[DebugInfo] Add num_extra_inhabitants to debug info #112590

augusto2112 · 2024-10-16T18:02:09Z

An extra inhabitant is a bit pattern that does not represent a valid
value for instances of a given type. The number of extra inhabitants is
the number of those bit configurations.

This is used by Swift to save space when composing types. For example,
because Bool only needs 2 bit patterns to represent all of its values
(true and false), an Optional only occupies 1 byte in memory by
using a bit configuration that is unused by Bool. Which bit patterns are
unused are part of the ABI of the language.

Since Swift generics are not monomorphized, by using dynamic libraries
you can have generic types whose size, alignment, etc, are known only
at runtime (which is why this feature is needed).

This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF
as an Apple extension.

llvmbot · 2024-10-16T18:02:54Z

@llvm/pr-subscribers-debuginfo

Author: Augusto Noronha (augusto2112)

Changes

An extra inhabitant is a bit pattern that does not represent a valid value for instances of a given type. The number of extra inhabitants is the number of those bit configurations.

This is used by Swift to save space when composing types. For example, because Bool only needs 2 bit patterns to represent all of its values (true and false), an Optional<Bool> only occupies 1 byte in memory by using a bit configuration that is unused by Bool.

This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF as an Apple extension.

Patch is 55.36 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/112590.diff

15 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/Dwarf.def (+1)
(modified) llvm/include/llvm/IR/DIBuilder.h (+10-2)
(modified) llvm/include/llvm/IR/DebugInfoMetadata.h (+73-54)
(modified) llvm/lib/AsmParser/LLParser.cpp (+11-7)
(modified) llvm/lib/Bitcode/Reader/MetadataLoader.cpp (+9-7)
(modified) llvm/lib/Bitcode/Writer/BitcodeWriter.cpp (+2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (+8)
(modified) llvm/lib/IR/AsmWriter.cpp (+2)
(modified) llvm/lib/IR/DIBuilder.cpp (+9-5)
(modified) llvm/lib/IR/DebugInfoMetadata.cpp (+28-25)
(modified) llvm/lib/IR/LLVMContextImpl.h (+18-8)
(modified) llvm/test/Assembler/debug-info.ll (+8-2)
(added) llvm/test/DebugInfo/AArch64/num_extra_inhabitants.ll (+30)
(modified) llvm/unittests/IR/DebugTypeODRUniquingTest.cpp (+18-17)
(modified) llvm/unittests/IR/MetadataTest.cpp (+19-14)

diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.def b/llvm/include/llvm/BinaryFormat/Dwarf.def
index d55947fc5103ac..66b397b1935943 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.def
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.def
@@ -636,6 +636,7 @@ HANDLE_DW_AT(0x3fed, APPLE_property, 0, APPLE)
 HANDLE_DW_AT(0x3fee, APPLE_objc_direct, 0, APPLE)
 HANDLE_DW_AT(0x3fef, APPLE_sdk, 0, APPLE)
 HANDLE_DW_AT(0x3ff0, APPLE_origin, 0, APPLE)
+HANDLE_DW_AT(0x3ff1, APPLE_num_extra_inhabitants, 0, APPLE)
 
 // Attribute form encodings.
 HANDLE_DW_FORM(0x01, addr, 2, DWARF)
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index a5655f630fc4f0..6b311b61152b2a 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -225,9 +225,13 @@ namespace llvm {
     /// \param SizeInBits  Size of the type.
     /// \param Encoding    DWARF encoding code, e.g., dwarf::DW_ATE_float.
     /// \param Flags       Optional DWARF attributes, e.g., DW_AT_endianity.
+    /// \param NumExtraInhabitants The number of extra inhabitants of the type.
+    /// An extra inhabitant is a bit pattern that does not represent a valid
+    /// value for instances of a given type.
     DIBasicType *createBasicType(StringRef Name, uint64_t SizeInBits,
                                  unsigned Encoding,
-                                 DINode::DIFlags Flags = DINode::FlagZero);
+                                 DINode::DIFlags Flags = DINode::FlagZero,
+                                 uint32_t NumExtraInhabitants = 0);
 
     /// Create debugging information entry for a string
     /// type.
@@ -484,11 +488,15 @@ namespace llvm {
     /// \param Elements     Struct elements.
     /// \param RunTimeLang  Optional parameter, Objective-C runtime version.
     /// \param UniqueIdentifier A unique identifier for the struct.
+    /// \param NumExtraInhabitants The number of extra inhabitants of the type.
+    /// An extra inhabitant is a bit pattern that does not represent a valid
+    /// value for instances of a given type.
     DICompositeType *createStructType(
         DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
         uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
         DIType *DerivedFrom, DINodeArray Elements, unsigned RunTimeLang = 0,
-        DIType *VTableHolder = nullptr, StringRef UniqueIdentifier = "");
+        DIType *VTableHolder = nullptr, StringRef UniqueIdentifier = "", 
+        uint32_t NumExtraInhabitants = 0);
 
     /// Create debugging information entry for an union.
     /// \param Scope        Scope in which this union is defined.
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index d2b4e900438d37..1043a5cf24bd76 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -712,31 +712,38 @@ class DIType : public DIScope {
   DIFlags Flags;
   uint64_t SizeInBits;
   uint64_t OffsetInBits;
+  uint32_t NumExtraInhabitants;
 
 protected:
   DIType(LLVMContext &C, unsigned ID, StorageType Storage, unsigned Tag,
          unsigned Line, uint64_t SizeInBits, uint32_t AlignInBits,
-         uint64_t OffsetInBits, DIFlags Flags, ArrayRef<Metadata *> Ops)
+         uint64_t OffsetInBits, uint32_t NumExtraInhabitants, DIFlags Flags,
+         ArrayRef<Metadata *> Ops)
       : DIScope(C, ID, Storage, Tag, Ops) {
-    init(Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    init(Line, SizeInBits, AlignInBits, OffsetInBits, NumExtraInhabitants,
+         Flags);
   }
   ~DIType() = default;
 
   void init(unsigned Line, uint64_t SizeInBits, uint32_t AlignInBits,
-            uint64_t OffsetInBits, DIFlags Flags) {
+            uint64_t OffsetInBits, uint32_t NumExtraInhabitants,
+            DIFlags Flags) {
     this->Line = Line;
     this->Flags = Flags;
     this->SizeInBits = SizeInBits;
     this->SubclassData32 = AlignInBits;
     this->OffsetInBits = OffsetInBits;
+    this->NumExtraInhabitants = NumExtraInhabitants;
   }
 
   /// Change fields in place.
   void mutate(unsigned Tag, unsigned Line, uint64_t SizeInBits,
-              uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags) {
+              uint32_t AlignInBits, uint64_t OffsetInBits,
+              uint32_t NumExtraInhabitants, DIFlags Flags) {
     assert(isDistinct() && "Only distinct nodes can mutate");
     setTag(Tag);
-    init(Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    init(Line, SizeInBits, AlignInBits, OffsetInBits, NumExtraInhabitants,
+         Flags);
   }
 
 public:
@@ -749,6 +756,7 @@ class DIType : public DIScope {
   uint32_t getAlignInBits() const;
   uint32_t getAlignInBytes() const { return getAlignInBits() / CHAR_BIT; }
   uint64_t getOffsetInBits() const { return OffsetInBits; }
+  uint32_t getNumExtraInhabitants() const { return NumExtraInhabitants; }
   DIFlags getFlags() const { return Flags; }
 
   DIScope *getScope() const { return cast_or_null<DIScope>(getRawScope()); }
@@ -820,49 +828,55 @@ class DIBasicType : public DIType {
 
   DIBasicType(LLVMContext &C, StorageType Storage, unsigned Tag,
               uint64_t SizeInBits, uint32_t AlignInBits, unsigned Encoding,
-              DIFlags Flags, ArrayRef<Metadata *> Ops)
+              uint32_t NumExtraInhabitants, DIFlags Flags,
+              ArrayRef<Metadata *> Ops)
       : DIType(C, DIBasicTypeKind, Storage, Tag, 0, SizeInBits, AlignInBits, 0,
-               Flags, Ops),
+               NumExtraInhabitants, Flags, Ops),
         Encoding(Encoding) {}
   ~DIBasicType() = default;
 
   static DIBasicType *getImpl(LLVMContext &Context, unsigned Tag,
                               StringRef Name, uint64_t SizeInBits,
                               uint32_t AlignInBits, unsigned Encoding,
-                              DIFlags Flags, StorageType Storage,
-                              bool ShouldCreate = true) {
+                              uint32_t NumExtraInhabitants, DIFlags Flags,
+                              StorageType Storage, bool ShouldCreate = true) {
     return getImpl(Context, Tag, getCanonicalMDString(Context, Name),
-                   SizeInBits, AlignInBits, Encoding, Flags, Storage,
-                   ShouldCreate);
+                   SizeInBits, AlignInBits, Encoding, NumExtraInhabitants,
+                   Flags, Storage, ShouldCreate);
   }
   static DIBasicType *getImpl(LLVMContext &Context, unsigned Tag,
                               MDString *Name, uint64_t SizeInBits,
                               uint32_t AlignInBits, unsigned Encoding,
-                              DIFlags Flags, StorageType Storage,
-                              bool ShouldCreate = true);
+                              uint32_t NumExtraInhabitants, DIFlags Flags,
+                              StorageType Storage, bool ShouldCreate = true);
 
   TempDIBasicType cloneImpl() const {
     return getTemporary(getContext(), getTag(), getName(), getSizeInBits(),
-                        getAlignInBits(), getEncoding(), getFlags());
+                        getAlignInBits(), getEncoding(),
+                        getNumExtraInhabitants(), getFlags());
   }
 
 public:
   DEFINE_MDNODE_GET(DIBasicType, (unsigned Tag, StringRef Name),
-                    (Tag, Name, 0, 0, 0, FlagZero))
+                    (Tag, Name, 0, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, StringRef Name, uint64_t SizeInBits),
-                    (Tag, Name, SizeInBits, 0, 0, FlagZero))
+                    (Tag, Name, SizeInBits, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, MDString *Name, uint64_t SizeInBits),
-                    (Tag, Name, SizeInBits, 0, 0, FlagZero))
+                    (Tag, Name, SizeInBits, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, StringRef Name, uint64_t SizeInBits,
-                     uint32_t AlignInBits, unsigned Encoding, DIFlags Flags),
-                    (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags))
+                     uint32_t AlignInBits, unsigned Encoding,
+                     uint32_t NumExtraInhabitants, DIFlags Flags),
+                    (Tag, Name, SizeInBits, AlignInBits, Encoding,
+                     NumExtraInhabitants, Flags))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, MDString *Name, uint64_t SizeInBits,
-                     uint32_t AlignInBits, unsigned Encoding, DIFlags Flags),
-                    (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags))
+                     uint32_t AlignInBits, unsigned Encoding,
+                     uint32_t NumExtraInhabitants, DIFlags Flags),
+                    (Tag, Name, SizeInBits, AlignInBits, Encoding,
+                     NumExtraInhabitants, Flags))
 
   TempDIBasicType clone() const { return cloneImpl(); }
 
@@ -890,7 +904,7 @@ class DIStringType : public DIType {
                uint64_t SizeInBits, uint32_t AlignInBits, unsigned Encoding,
                ArrayRef<Metadata *> Ops)
       : DIType(C, DIStringTypeKind, Storage, Tag, 0, SizeInBits, AlignInBits, 0,
-               FlagZero, Ops),
+               0, FlagZero, Ops),
         Encoding(Encoding) {}
   ~DIStringType() = default;
 
@@ -1016,7 +1030,7 @@ class DIDerivedType : public DIType {
                 std::optional<PtrAuthData> PtrAuthData, DIFlags Flags,
                 ArrayRef<Metadata *> Ops)
       : DIType(C, DIDerivedTypeKind, Storage, Tag, Line, SizeInBits,
-               AlignInBits, OffsetInBits, Flags, Ops),
+               AlignInBits, OffsetInBits, 0, Flags, Ops),
         DWARFAddressSpace(DWARFAddressSpace) {
     if (PtrAuthData)
       SubclassData32 = PtrAuthData->RawData;
@@ -1157,39 +1171,43 @@ class DICompositeType : public DIType {
 
   DICompositeType(LLVMContext &C, StorageType Storage, unsigned Tag,
                   unsigned Line, unsigned RuntimeLang, uint64_t SizeInBits,
-                  uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags,
+                  uint32_t AlignInBits, uint64_t OffsetInBits,
+                  uint32_t NumExtraInhabitants, DIFlags Flags,
                   ArrayRef<Metadata *> Ops)
       : DIType(C, DICompositeTypeKind, Storage, Tag, Line, SizeInBits,
-               AlignInBits, OffsetInBits, Flags, Ops),
+               AlignInBits, OffsetInBits, NumExtraInhabitants, Flags, Ops),
         RuntimeLang(RuntimeLang) {}
   ~DICompositeType() = default;
 
   /// Change fields in place.
   void mutate(unsigned Tag, unsigned Line, unsigned RuntimeLang,
               uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
-              DIFlags Flags) {
+              uint32_t NumExtraInhabitants, DIFlags Flags) {
     assert(isDistinct() && "Only distinct nodes can mutate");
     assert(getRawIdentifier() && "Only ODR-uniqued nodes should mutate");
     this->RuntimeLang = RuntimeLang;
-    DIType::mutate(Tag, Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    DIType::mutate(Tag, Line, SizeInBits, AlignInBits, OffsetInBits,
+                   NumExtraInhabitants, Flags);
   }
 
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, StringRef Name, Metadata *File,
           unsigned Line, DIScope *Scope, DIType *BaseType, uint64_t SizeInBits,
-          uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags,
-          DINodeArray Elements, unsigned RuntimeLang, DIType *VTableHolder,
+          uint32_t AlignInBits, uint64_t OffsetInBits,
+          uint32_t NumExtraInhabitants, DIFlags Flags, DINodeArray Elements,
+          unsigned RuntimeLang, DIType *VTableHolder,
           DITemplateParameterArray TemplateParams, StringRef Identifier,
           DIDerivedType *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
           DINodeArray Annotations, StorageType Storage,
           bool ShouldCreate = true) {
-    return getImpl(
-        Context, Tag, getCanonicalMDString(Context, Name), File, Line, Scope,
-        BaseType, SizeInBits, AlignInBits, OffsetInBits, Flags, Elements.get(),
-        RuntimeLang, VTableHolder, TemplateParams.get(),
-        getCanonicalMDString(Context, Identifier), Discriminator, DataLocation,
-        Associated, Allocated, Rank, Annotations.get(), Storage, ShouldCreate);
+    return getImpl(Context, Tag, getCanonicalMDString(Context, Name), File,
+                   Line, Scope, BaseType, SizeInBits, AlignInBits, OffsetInBits,
+                   Flags, Elements.get(), RuntimeLang, VTableHolder,
+                   TemplateParams.get(),
+                   getCanonicalMDString(Context, Identifier), Discriminator,
+                   DataLocation, Associated, Allocated, Rank, Annotations.get(),
+                   NumExtraInhabitants, Storage, ShouldCreate);
   }
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, MDString *Name, Metadata *File,
@@ -1199,7 +1217,8 @@ class DICompositeType : public DIType {
           Metadata *VTableHolder, Metadata *TemplateParams,
           MDString *Identifier, Metadata *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
-          Metadata *Annotations, StorageType Storage, bool ShouldCreate = true);
+          Metadata *Annotations, uint32_t NumExtraInhabitants,
+          StorageType Storage, bool ShouldCreate = true);
 
   TempDICompositeType cloneImpl() const {
     return getTemporary(
@@ -1208,7 +1227,7 @@ class DICompositeType : public DIType {
         getFlags(), getElements(), getRuntimeLang(), getVTableHolder(),
         getTemplateParams(), getIdentifier(), getDiscriminator(),
         getRawDataLocation(), getRawAssociated(), getRawAllocated(),
-        getRawRank(), getAnnotations());
+        getRawRank(), getAnnotations(), getNumExtraInhabitants());
   }
 
 public:
@@ -1222,11 +1241,11 @@ class DICompositeType : public DIType {
        StringRef Identifier = "", DIDerivedType *Discriminator = nullptr,
        Metadata *DataLocation = nullptr, Metadata *Associated = nullptr,
        Metadata *Allocated = nullptr, Metadata *Rank = nullptr,
-       DINodeArray Annotations = nullptr),
+       DINodeArray Annotations = nullptr, uint32_t NumExtraInhabitants = 0),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
-       OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
-       Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations))
+       OffsetInBits, NumExtraInhabitants, Flags, Elements, RuntimeLang,
+       VTableHolder, TemplateParams, Identifier, Discriminator, DataLocation,
+       Associated, Allocated, Rank, Annotations))
   DEFINE_MDNODE_GET(
       DICompositeType,
       (unsigned Tag, MDString *Name, Metadata *File, unsigned Line,
@@ -1236,11 +1255,12 @@ class DICompositeType : public DIType {
        Metadata *TemplateParams = nullptr, MDString *Identifier = nullptr,
        Metadata *Discriminator = nullptr, Metadata *DataLocation = nullptr,
        Metadata *Associated = nullptr, Metadata *Allocated = nullptr,
-       Metadata *Rank = nullptr, Metadata *Annotations = nullptr),
+       Metadata *Rank = nullptr, Metadata *Annotations = nullptr,
+       uint32_t NumExtraInhabitants = 0),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
        OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
        Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations))
+       Annotations, NumExtraInhabitants))
 
   TempDICompositeType clone() const { return cloneImpl(); }
 
@@ -1255,8 +1275,8 @@ class DICompositeType : public DIType {
   getODRType(LLVMContext &Context, MDString &Identifier, unsigned Tag,
              MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
              Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
-             uint64_t OffsetInBits, DIFlags Flags, Metadata *Elements,
-             unsigned RuntimeLang, Metadata *VTableHolder,
+             uint64_t OffsetInBits, uint32_t NumExtraInhabitants, DIFlags Flags,
+             Metadata *Elements, unsigned RuntimeLang, Metadata *VTableHolder,
              Metadata *TemplateParams, Metadata *Discriminator,
              Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
              Metadata *Rank, Metadata *Annotations);
@@ -1272,15 +1292,14 @@ class DICompositeType : public DIType {
   ///
   /// If not \a LLVMContext::isODRUniquingDebugTypes(), this function returns
   /// nullptr.
-  static DICompositeType *
-  buildODRType(LLVMContext &Context, MDString &Identifier, unsigned Tag,
-               MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
-               Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
-               uint64_t OffsetInBits, DIFlags Flags, Metadata *Elements,
-               unsigned RuntimeLang, Metadata *VTableHolder,
-               Metadata *TemplateParams, Metadata *Discriminator,
-               Metadata *DataLocation, Metadata *Associated,
-               Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
+  static DICompositeType *buildODRType(
+      LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
+      Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,
+      uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
+      uint32_t NumExtraInhabitants, DIFlags Flags, Metadata *Elements,
+      unsigned RuntimeLang, Metadata *VTableHolder, Metadata *TemplateParams,
+      Metadata *Discriminator, Metadata *DataLocation, Metadata *Associated,
+      Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
 
   DIType *getBaseType() const { return cast_or_null<DIType>(getRawBaseType()); }
   DINodeArray getElements() const {
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 5b9bddeb7cfe82..af9155636a2239 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -5329,12 +5329,14 @@ bool LLParser::parseDIBasicType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(size, MDUnsignedField, (0, UINT64_MAX));                            \
   OPTIONAL(align, MDUnsignedField, (0, UINT32_MAX));                           \
   OPTIONAL(encoding, DwarfAttEncodingField, );                                 \
+  OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           \
   OPTIONAL(flags, DIFlagField, );
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
   Result = GET_OR_DISTINCT(DIBasicType, (Context, tag.Val, name.Val, size.Val,
-                                         align.Val, encoding.Val, flags.Val));
+                                         align.Val, encoding.Val,
+                                         num_extra_inhabitants.Val, flags.Val));
   return false;
 }
 
@@ -5432,7 +5434,8 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(associated, MDField, );                                             \
   OPTIONAL(allocated, MDField, );                                              \
   OPTIONAL(rank, MDSignedOrMDField, );                                         \
-  OPTIONAL(annotations, MDField, );
+  OPTIONAL(annotations, MDField, );                                            \
+  OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
@@ -5447,10 +5450,11 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   if (identifier.Val)
     if (auto *CT = DICompositeType::buildODRType(
             Context, *identifier.Val, tag.Val, name.Val, file.Val, line.Val,
-            scope.Val, baseType.Val, size.Val, align.Val, offset.Val, flags.Val,
-            elements.Val, runtimeLang.Val, vtableHolder.Val, templateParams.Val,
-            discriminator.Val, dataLocation.Val, associated.Val, allocated.Val,
-            Rank, annotations.Val)) {
+            scope.Val, baseType.Val, size.Val, align.Val, offset.Val,
+            num_extra_inhabitants.Val, flags.Val, elements.Val, runtimeLang.Val,
+            vtableHolder.Val, templateParams.Val, discriminator.Val,
+            dataLocation.Val, asso...
[truncated]

llvmbot · 2024-10-16T18:02:54Z

@llvm/pr-subscribers-llvm-ir

Author: Augusto Noronha (augusto2112)

Changes

An extra inhabitant is a bit pattern that does not represent a valid value for instances of a given type. The number of extra inhabitants is the number of those bit configurations.

This is used by Swift to save space when composing types. For example, because Bool only needs 2 bit patterns to represent all of its values (true and false), an Optional<Bool> only occupies 1 byte in memory by using a bit configuration that is unused by Bool.

This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF as an Apple extension.

Patch is 55.36 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/112590.diff

15 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/Dwarf.def (+1)
(modified) llvm/include/llvm/IR/DIBuilder.h (+10-2)
(modified) llvm/include/llvm/IR/DebugInfoMetadata.h (+73-54)
(modified) llvm/lib/AsmParser/LLParser.cpp (+11-7)
(modified) llvm/lib/Bitcode/Reader/MetadataLoader.cpp (+9-7)
(modified) llvm/lib/Bitcode/Writer/BitcodeWriter.cpp (+2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (+8)
(modified) llvm/lib/IR/AsmWriter.cpp (+2)
(modified) llvm/lib/IR/DIBuilder.cpp (+9-5)
(modified) llvm/lib/IR/DebugInfoMetadata.cpp (+28-25)
(modified) llvm/lib/IR/LLVMContextImpl.h (+18-8)
(modified) llvm/test/Assembler/debug-info.ll (+8-2)
(added) llvm/test/DebugInfo/AArch64/num_extra_inhabitants.ll (+30)
(modified) llvm/unittests/IR/DebugTypeODRUniquingTest.cpp (+18-17)
(modified) llvm/unittests/IR/MetadataTest.cpp (+19-14)

diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.def b/llvm/include/llvm/BinaryFormat/Dwarf.def
index d55947fc5103ac..66b397b1935943 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.def
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.def
@@ -636,6 +636,7 @@ HANDLE_DW_AT(0x3fed, APPLE_property, 0, APPLE)
 HANDLE_DW_AT(0x3fee, APPLE_objc_direct, 0, APPLE)
 HANDLE_DW_AT(0x3fef, APPLE_sdk, 0, APPLE)
 HANDLE_DW_AT(0x3ff0, APPLE_origin, 0, APPLE)
+HANDLE_DW_AT(0x3ff1, APPLE_num_extra_inhabitants, 0, APPLE)
 
 // Attribute form encodings.
 HANDLE_DW_FORM(0x01, addr, 2, DWARF)
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index a5655f630fc4f0..6b311b61152b2a 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -225,9 +225,13 @@ namespace llvm {
     /// \param SizeInBits  Size of the type.
     /// \param Encoding    DWARF encoding code, e.g., dwarf::DW_ATE_float.
     /// \param Flags       Optional DWARF attributes, e.g., DW_AT_endianity.
+    /// \param NumExtraInhabitants The number of extra inhabitants of the type.
+    /// An extra inhabitant is a bit pattern that does not represent a valid
+    /// value for instances of a given type.
     DIBasicType *createBasicType(StringRef Name, uint64_t SizeInBits,
                                  unsigned Encoding,
-                                 DINode::DIFlags Flags = DINode::FlagZero);
+                                 DINode::DIFlags Flags = DINode::FlagZero,
+                                 uint32_t NumExtraInhabitants = 0);
 
     /// Create debugging information entry for a string
     /// type.
@@ -484,11 +488,15 @@ namespace llvm {
     /// \param Elements     Struct elements.
     /// \param RunTimeLang  Optional parameter, Objective-C runtime version.
     /// \param UniqueIdentifier A unique identifier for the struct.
+    /// \param NumExtraInhabitants The number of extra inhabitants of the type.
+    /// An extra inhabitant is a bit pattern that does not represent a valid
+    /// value for instances of a given type.
     DICompositeType *createStructType(
         DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
         uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
         DIType *DerivedFrom, DINodeArray Elements, unsigned RunTimeLang = 0,
-        DIType *VTableHolder = nullptr, StringRef UniqueIdentifier = "");
+        DIType *VTableHolder = nullptr, StringRef UniqueIdentifier = "", 
+        uint32_t NumExtraInhabitants = 0);
 
     /// Create debugging information entry for an union.
     /// \param Scope        Scope in which this union is defined.
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index d2b4e900438d37..1043a5cf24bd76 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -712,31 +712,38 @@ class DIType : public DIScope {
   DIFlags Flags;
   uint64_t SizeInBits;
   uint64_t OffsetInBits;
+  uint32_t NumExtraInhabitants;
 
 protected:
   DIType(LLVMContext &C, unsigned ID, StorageType Storage, unsigned Tag,
          unsigned Line, uint64_t SizeInBits, uint32_t AlignInBits,
-         uint64_t OffsetInBits, DIFlags Flags, ArrayRef<Metadata *> Ops)
+         uint64_t OffsetInBits, uint32_t NumExtraInhabitants, DIFlags Flags,
+         ArrayRef<Metadata *> Ops)
       : DIScope(C, ID, Storage, Tag, Ops) {
-    init(Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    init(Line, SizeInBits, AlignInBits, OffsetInBits, NumExtraInhabitants,
+         Flags);
   }
   ~DIType() = default;
 
   void init(unsigned Line, uint64_t SizeInBits, uint32_t AlignInBits,
-            uint64_t OffsetInBits, DIFlags Flags) {
+            uint64_t OffsetInBits, uint32_t NumExtraInhabitants,
+            DIFlags Flags) {
     this->Line = Line;
     this->Flags = Flags;
     this->SizeInBits = SizeInBits;
     this->SubclassData32 = AlignInBits;
     this->OffsetInBits = OffsetInBits;
+    this->NumExtraInhabitants = NumExtraInhabitants;
   }
 
   /// Change fields in place.
   void mutate(unsigned Tag, unsigned Line, uint64_t SizeInBits,
-              uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags) {
+              uint32_t AlignInBits, uint64_t OffsetInBits,
+              uint32_t NumExtraInhabitants, DIFlags Flags) {
     assert(isDistinct() && "Only distinct nodes can mutate");
     setTag(Tag);
-    init(Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    init(Line, SizeInBits, AlignInBits, OffsetInBits, NumExtraInhabitants,
+         Flags);
   }
 
 public:
@@ -749,6 +756,7 @@ class DIType : public DIScope {
   uint32_t getAlignInBits() const;
   uint32_t getAlignInBytes() const { return getAlignInBits() / CHAR_BIT; }
   uint64_t getOffsetInBits() const { return OffsetInBits; }
+  uint32_t getNumExtraInhabitants() const { return NumExtraInhabitants; }
   DIFlags getFlags() const { return Flags; }
 
   DIScope *getScope() const { return cast_or_null<DIScope>(getRawScope()); }
@@ -820,49 +828,55 @@ class DIBasicType : public DIType {
 
   DIBasicType(LLVMContext &C, StorageType Storage, unsigned Tag,
               uint64_t SizeInBits, uint32_t AlignInBits, unsigned Encoding,
-              DIFlags Flags, ArrayRef<Metadata *> Ops)
+              uint32_t NumExtraInhabitants, DIFlags Flags,
+              ArrayRef<Metadata *> Ops)
       : DIType(C, DIBasicTypeKind, Storage, Tag, 0, SizeInBits, AlignInBits, 0,
-               Flags, Ops),
+               NumExtraInhabitants, Flags, Ops),
         Encoding(Encoding) {}
   ~DIBasicType() = default;
 
   static DIBasicType *getImpl(LLVMContext &Context, unsigned Tag,
                               StringRef Name, uint64_t SizeInBits,
                               uint32_t AlignInBits, unsigned Encoding,
-                              DIFlags Flags, StorageType Storage,
-                              bool ShouldCreate = true) {
+                              uint32_t NumExtraInhabitants, DIFlags Flags,
+                              StorageType Storage, bool ShouldCreate = true) {
     return getImpl(Context, Tag, getCanonicalMDString(Context, Name),
-                   SizeInBits, AlignInBits, Encoding, Flags, Storage,
-                   ShouldCreate);
+                   SizeInBits, AlignInBits, Encoding, NumExtraInhabitants,
+                   Flags, Storage, ShouldCreate);
   }
   static DIBasicType *getImpl(LLVMContext &Context, unsigned Tag,
                               MDString *Name, uint64_t SizeInBits,
                               uint32_t AlignInBits, unsigned Encoding,
-                              DIFlags Flags, StorageType Storage,
-                              bool ShouldCreate = true);
+                              uint32_t NumExtraInhabitants, DIFlags Flags,
+                              StorageType Storage, bool ShouldCreate = true);
 
   TempDIBasicType cloneImpl() const {
     return getTemporary(getContext(), getTag(), getName(), getSizeInBits(),
-                        getAlignInBits(), getEncoding(), getFlags());
+                        getAlignInBits(), getEncoding(),
+                        getNumExtraInhabitants(), getFlags());
   }
 
 public:
   DEFINE_MDNODE_GET(DIBasicType, (unsigned Tag, StringRef Name),
-                    (Tag, Name, 0, 0, 0, FlagZero))
+                    (Tag, Name, 0, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, StringRef Name, uint64_t SizeInBits),
-                    (Tag, Name, SizeInBits, 0, 0, FlagZero))
+                    (Tag, Name, SizeInBits, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, MDString *Name, uint64_t SizeInBits),
-                    (Tag, Name, SizeInBits, 0, 0, FlagZero))
+                    (Tag, Name, SizeInBits, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, StringRef Name, uint64_t SizeInBits,
-                     uint32_t AlignInBits, unsigned Encoding, DIFlags Flags),
-                    (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags))
+                     uint32_t AlignInBits, unsigned Encoding,
+                     uint32_t NumExtraInhabitants, DIFlags Flags),
+                    (Tag, Name, SizeInBits, AlignInBits, Encoding,
+                     NumExtraInhabitants, Flags))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, MDString *Name, uint64_t SizeInBits,
-                     uint32_t AlignInBits, unsigned Encoding, DIFlags Flags),
-                    (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags))
+                     uint32_t AlignInBits, unsigned Encoding,
+                     uint32_t NumExtraInhabitants, DIFlags Flags),
+                    (Tag, Name, SizeInBits, AlignInBits, Encoding,
+                     NumExtraInhabitants, Flags))
 
   TempDIBasicType clone() const { return cloneImpl(); }
 
@@ -890,7 +904,7 @@ class DIStringType : public DIType {
                uint64_t SizeInBits, uint32_t AlignInBits, unsigned Encoding,
                ArrayRef<Metadata *> Ops)
       : DIType(C, DIStringTypeKind, Storage, Tag, 0, SizeInBits, AlignInBits, 0,
-               FlagZero, Ops),
+               0, FlagZero, Ops),
         Encoding(Encoding) {}
   ~DIStringType() = default;
 
@@ -1016,7 +1030,7 @@ class DIDerivedType : public DIType {
                 std::optional<PtrAuthData> PtrAuthData, DIFlags Flags,
                 ArrayRef<Metadata *> Ops)
       : DIType(C, DIDerivedTypeKind, Storage, Tag, Line, SizeInBits,
-               AlignInBits, OffsetInBits, Flags, Ops),
+               AlignInBits, OffsetInBits, 0, Flags, Ops),
         DWARFAddressSpace(DWARFAddressSpace) {
     if (PtrAuthData)
       SubclassData32 = PtrAuthData->RawData;
@@ -1157,39 +1171,43 @@ class DICompositeType : public DIType {
 
   DICompositeType(LLVMContext &C, StorageType Storage, unsigned Tag,
                   unsigned Line, unsigned RuntimeLang, uint64_t SizeInBits,
-                  uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags,
+                  uint32_t AlignInBits, uint64_t OffsetInBits,
+                  uint32_t NumExtraInhabitants, DIFlags Flags,
                   ArrayRef<Metadata *> Ops)
       : DIType(C, DICompositeTypeKind, Storage, Tag, Line, SizeInBits,
-               AlignInBits, OffsetInBits, Flags, Ops),
+               AlignInBits, OffsetInBits, NumExtraInhabitants, Flags, Ops),
         RuntimeLang(RuntimeLang) {}
   ~DICompositeType() = default;
 
   /// Change fields in place.
   void mutate(unsigned Tag, unsigned Line, unsigned RuntimeLang,
               uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
-              DIFlags Flags) {
+              uint32_t NumExtraInhabitants, DIFlags Flags) {
     assert(isDistinct() && "Only distinct nodes can mutate");
     assert(getRawIdentifier() && "Only ODR-uniqued nodes should mutate");
     this->RuntimeLang = RuntimeLang;
-    DIType::mutate(Tag, Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    DIType::mutate(Tag, Line, SizeInBits, AlignInBits, OffsetInBits,
+                   NumExtraInhabitants, Flags);
   }
 
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, StringRef Name, Metadata *File,
           unsigned Line, DIScope *Scope, DIType *BaseType, uint64_t SizeInBits,
-          uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags,
-          DINodeArray Elements, unsigned RuntimeLang, DIType *VTableHolder,
+          uint32_t AlignInBits, uint64_t OffsetInBits,
+          uint32_t NumExtraInhabitants, DIFlags Flags, DINodeArray Elements,
+          unsigned RuntimeLang, DIType *VTableHolder,
           DITemplateParameterArray TemplateParams, StringRef Identifier,
           DIDerivedType *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
           DINodeArray Annotations, StorageType Storage,
           bool ShouldCreate = true) {
-    return getImpl(
-        Context, Tag, getCanonicalMDString(Context, Name), File, Line, Scope,
-        BaseType, SizeInBits, AlignInBits, OffsetInBits, Flags, Elements.get(),
-        RuntimeLang, VTableHolder, TemplateParams.get(),
-        getCanonicalMDString(Context, Identifier), Discriminator, DataLocation,
-        Associated, Allocated, Rank, Annotations.get(), Storage, ShouldCreate);
+    return getImpl(Context, Tag, getCanonicalMDString(Context, Name), File,
+                   Line, Scope, BaseType, SizeInBits, AlignInBits, OffsetInBits,
+                   Flags, Elements.get(), RuntimeLang, VTableHolder,
+                   TemplateParams.get(),
+                   getCanonicalMDString(Context, Identifier), Discriminator,
+                   DataLocation, Associated, Allocated, Rank, Annotations.get(),
+                   NumExtraInhabitants, Storage, ShouldCreate);
   }
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, MDString *Name, Metadata *File,
@@ -1199,7 +1217,8 @@ class DICompositeType : public DIType {
           Metadata *VTableHolder, Metadata *TemplateParams,
           MDString *Identifier, Metadata *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
-          Metadata *Annotations, StorageType Storage, bool ShouldCreate = true);
+          Metadata *Annotations, uint32_t NumExtraInhabitants,
+          StorageType Storage, bool ShouldCreate = true);
 
   TempDICompositeType cloneImpl() const {
     return getTemporary(
@@ -1208,7 +1227,7 @@ class DICompositeType : public DIType {
         getFlags(), getElements(), getRuntimeLang(), getVTableHolder(),
         getTemplateParams(), getIdentifier(), getDiscriminator(),
         getRawDataLocation(), getRawAssociated(), getRawAllocated(),
-        getRawRank(), getAnnotations());
+        getRawRank(), getAnnotations(), getNumExtraInhabitants());
   }
 
 public:
@@ -1222,11 +1241,11 @@ class DICompositeType : public DIType {
        StringRef Identifier = "", DIDerivedType *Discriminator = nullptr,
        Metadata *DataLocation = nullptr, Metadata *Associated = nullptr,
        Metadata *Allocated = nullptr, Metadata *Rank = nullptr,
-       DINodeArray Annotations = nullptr),
+       DINodeArray Annotations = nullptr, uint32_t NumExtraInhabitants = 0),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
-       OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
-       Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations))
+       OffsetInBits, NumExtraInhabitants, Flags, Elements, RuntimeLang,
+       VTableHolder, TemplateParams, Identifier, Discriminator, DataLocation,
+       Associated, Allocated, Rank, Annotations))
   DEFINE_MDNODE_GET(
       DICompositeType,
       (unsigned Tag, MDString *Name, Metadata *File, unsigned Line,
@@ -1236,11 +1255,12 @@ class DICompositeType : public DIType {
        Metadata *TemplateParams = nullptr, MDString *Identifier = nullptr,
        Metadata *Discriminator = nullptr, Metadata *DataLocation = nullptr,
        Metadata *Associated = nullptr, Metadata *Allocated = nullptr,
-       Metadata *Rank = nullptr, Metadata *Annotations = nullptr),
+       Metadata *Rank = nullptr, Metadata *Annotations = nullptr,
+       uint32_t NumExtraInhabitants = 0),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
        OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
        Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations))
+       Annotations, NumExtraInhabitants))
 
   TempDICompositeType clone() const { return cloneImpl(); }
 
@@ -1255,8 +1275,8 @@ class DICompositeType : public DIType {
   getODRType(LLVMContext &Context, MDString &Identifier, unsigned Tag,
              MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
              Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
-             uint64_t OffsetInBits, DIFlags Flags, Metadata *Elements,
-             unsigned RuntimeLang, Metadata *VTableHolder,
+             uint64_t OffsetInBits, uint32_t NumExtraInhabitants, DIFlags Flags,
+             Metadata *Elements, unsigned RuntimeLang, Metadata *VTableHolder,
              Metadata *TemplateParams, Metadata *Discriminator,
              Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
              Metadata *Rank, Metadata *Annotations);
@@ -1272,15 +1292,14 @@ class DICompositeType : public DIType {
   ///
   /// If not \a LLVMContext::isODRUniquingDebugTypes(), this function returns
   /// nullptr.
-  static DICompositeType *
-  buildODRType(LLVMContext &Context, MDString &Identifier, unsigned Tag,
-               MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
-               Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
-               uint64_t OffsetInBits, DIFlags Flags, Metadata *Elements,
-               unsigned RuntimeLang, Metadata *VTableHolder,
-               Metadata *TemplateParams, Metadata *Discriminator,
-               Metadata *DataLocation, Metadata *Associated,
-               Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
+  static DICompositeType *buildODRType(
+      LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
+      Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,
+      uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
+      uint32_t NumExtraInhabitants, DIFlags Flags, Metadata *Elements,
+      unsigned RuntimeLang, Metadata *VTableHolder, Metadata *TemplateParams,
+      Metadata *Discriminator, Metadata *DataLocation, Metadata *Associated,
+      Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
 
   DIType *getBaseType() const { return cast_or_null<DIType>(getRawBaseType()); }
   DINodeArray getElements() const {
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 5b9bddeb7cfe82..af9155636a2239 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -5329,12 +5329,14 @@ bool LLParser::parseDIBasicType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(size, MDUnsignedField, (0, UINT64_MAX));                            \
   OPTIONAL(align, MDUnsignedField, (0, UINT32_MAX));                           \
   OPTIONAL(encoding, DwarfAttEncodingField, );                                 \
+  OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           \
   OPTIONAL(flags, DIFlagField, );
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
   Result = GET_OR_DISTINCT(DIBasicType, (Context, tag.Val, name.Val, size.Val,
-                                         align.Val, encoding.Val, flags.Val));
+                                         align.Val, encoding.Val,
+                                         num_extra_inhabitants.Val, flags.Val));
   return false;
 }
 
@@ -5432,7 +5434,8 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(associated, MDField, );                                             \
   OPTIONAL(allocated, MDField, );                                              \
   OPTIONAL(rank, MDSignedOrMDField, );                                         \
-  OPTIONAL(annotations, MDField, );
+  OPTIONAL(annotations, MDField, );                                            \
+  OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
@@ -5447,10 +5450,11 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   if (identifier.Val)
     if (auto *CT = DICompositeType::buildODRType(
             Context, *identifier.Val, tag.Val, name.Val, file.Val, line.Val,
-            scope.Val, baseType.Val, size.Val, align.Val, offset.Val, flags.Val,
-            elements.Val, runtimeLang.Val, vtableHolder.Val, templateParams.Val,
-            discriminator.Val, dataLocation.Val, associated.Val, allocated.Val,
-            Rank, annotations.Val)) {
+            scope.Val, baseType.Val, size.Val, align.Val, offset.Val,
+            num_extra_inhabitants.Val, flags.Val, elements.Val, runtimeLang.Val,
+            vtableHolder.Val, templateParams.Val, discriminator.Val,
+            dataLocation.Val, asso...
[truncated]

llvmbot · 2024-10-16T18:02:55Z

@llvm/pr-subscribers-llvm-binary-utilities

Author: Augusto Noronha (augusto2112)

Changes

An extra inhabitant is a bit pattern that does not represent a valid value for instances of a given type. The number of extra inhabitants is the number of those bit configurations.

This is used by Swift to save space when composing types. For example, because Bool only needs 2 bit patterns to represent all of its values (true and false), an Optional<Bool> only occupies 1 byte in memory by using a bit configuration that is unused by Bool.

This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF as an Apple extension.

Patch is 55.36 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/112590.diff

15 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/Dwarf.def (+1)
(modified) llvm/include/llvm/IR/DIBuilder.h (+10-2)
(modified) llvm/include/llvm/IR/DebugInfoMetadata.h (+73-54)
(modified) llvm/lib/AsmParser/LLParser.cpp (+11-7)
(modified) llvm/lib/Bitcode/Reader/MetadataLoader.cpp (+9-7)
(modified) llvm/lib/Bitcode/Writer/BitcodeWriter.cpp (+2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (+8)
(modified) llvm/lib/IR/AsmWriter.cpp (+2)
(modified) llvm/lib/IR/DIBuilder.cpp (+9-5)
(modified) llvm/lib/IR/DebugInfoMetadata.cpp (+28-25)
(modified) llvm/lib/IR/LLVMContextImpl.h (+18-8)
(modified) llvm/test/Assembler/debug-info.ll (+8-2)
(added) llvm/test/DebugInfo/AArch64/num_extra_inhabitants.ll (+30)
(modified) llvm/unittests/IR/DebugTypeODRUniquingTest.cpp (+18-17)
(modified) llvm/unittests/IR/MetadataTest.cpp (+19-14)

diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.def b/llvm/include/llvm/BinaryFormat/Dwarf.def
index d55947fc5103ac..66b397b1935943 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.def
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.def
@@ -636,6 +636,7 @@ HANDLE_DW_AT(0x3fed, APPLE_property, 0, APPLE)
 HANDLE_DW_AT(0x3fee, APPLE_objc_direct, 0, APPLE)
 HANDLE_DW_AT(0x3fef, APPLE_sdk, 0, APPLE)
 HANDLE_DW_AT(0x3ff0, APPLE_origin, 0, APPLE)
+HANDLE_DW_AT(0x3ff1, APPLE_num_extra_inhabitants, 0, APPLE)
 
 // Attribute form encodings.
 HANDLE_DW_FORM(0x01, addr, 2, DWARF)
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index a5655f630fc4f0..6b311b61152b2a 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -225,9 +225,13 @@ namespace llvm {
     /// \param SizeInBits  Size of the type.
     /// \param Encoding    DWARF encoding code, e.g., dwarf::DW_ATE_float.
     /// \param Flags       Optional DWARF attributes, e.g., DW_AT_endianity.
+    /// \param NumExtraInhabitants The number of extra inhabitants of the type.
+    /// An extra inhabitant is a bit pattern that does not represent a valid
+    /// value for instances of a given type.
     DIBasicType *createBasicType(StringRef Name, uint64_t SizeInBits,
                                  unsigned Encoding,
-                                 DINode::DIFlags Flags = DINode::FlagZero);
+                                 DINode::DIFlags Flags = DINode::FlagZero,
+                                 uint32_t NumExtraInhabitants = 0);
 
     /// Create debugging information entry for a string
     /// type.
@@ -484,11 +488,15 @@ namespace llvm {
     /// \param Elements     Struct elements.
     /// \param RunTimeLang  Optional parameter, Objective-C runtime version.
     /// \param UniqueIdentifier A unique identifier for the struct.
+    /// \param NumExtraInhabitants The number of extra inhabitants of the type.
+    /// An extra inhabitant is a bit pattern that does not represent a valid
+    /// value for instances of a given type.
     DICompositeType *createStructType(
         DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
         uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
         DIType *DerivedFrom, DINodeArray Elements, unsigned RunTimeLang = 0,
-        DIType *VTableHolder = nullptr, StringRef UniqueIdentifier = "");
+        DIType *VTableHolder = nullptr, StringRef UniqueIdentifier = "", 
+        uint32_t NumExtraInhabitants = 0);
 
     /// Create debugging information entry for an union.
     /// \param Scope        Scope in which this union is defined.
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index d2b4e900438d37..1043a5cf24bd76 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -712,31 +712,38 @@ class DIType : public DIScope {
   DIFlags Flags;
   uint64_t SizeInBits;
   uint64_t OffsetInBits;
+  uint32_t NumExtraInhabitants;
 
 protected:
   DIType(LLVMContext &C, unsigned ID, StorageType Storage, unsigned Tag,
          unsigned Line, uint64_t SizeInBits, uint32_t AlignInBits,
-         uint64_t OffsetInBits, DIFlags Flags, ArrayRef<Metadata *> Ops)
+         uint64_t OffsetInBits, uint32_t NumExtraInhabitants, DIFlags Flags,
+         ArrayRef<Metadata *> Ops)
       : DIScope(C, ID, Storage, Tag, Ops) {
-    init(Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    init(Line, SizeInBits, AlignInBits, OffsetInBits, NumExtraInhabitants,
+         Flags);
   }
   ~DIType() = default;
 
   void init(unsigned Line, uint64_t SizeInBits, uint32_t AlignInBits,
-            uint64_t OffsetInBits, DIFlags Flags) {
+            uint64_t OffsetInBits, uint32_t NumExtraInhabitants,
+            DIFlags Flags) {
     this->Line = Line;
     this->Flags = Flags;
     this->SizeInBits = SizeInBits;
     this->SubclassData32 = AlignInBits;
     this->OffsetInBits = OffsetInBits;
+    this->NumExtraInhabitants = NumExtraInhabitants;
   }
 
   /// Change fields in place.
   void mutate(unsigned Tag, unsigned Line, uint64_t SizeInBits,
-              uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags) {
+              uint32_t AlignInBits, uint64_t OffsetInBits,
+              uint32_t NumExtraInhabitants, DIFlags Flags) {
     assert(isDistinct() && "Only distinct nodes can mutate");
     setTag(Tag);
-    init(Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    init(Line, SizeInBits, AlignInBits, OffsetInBits, NumExtraInhabitants,
+         Flags);
   }
 
 public:
@@ -749,6 +756,7 @@ class DIType : public DIScope {
   uint32_t getAlignInBits() const;
   uint32_t getAlignInBytes() const { return getAlignInBits() / CHAR_BIT; }
   uint64_t getOffsetInBits() const { return OffsetInBits; }
+  uint32_t getNumExtraInhabitants() const { return NumExtraInhabitants; }
   DIFlags getFlags() const { return Flags; }
 
   DIScope *getScope() const { return cast_or_null<DIScope>(getRawScope()); }
@@ -820,49 +828,55 @@ class DIBasicType : public DIType {
 
   DIBasicType(LLVMContext &C, StorageType Storage, unsigned Tag,
               uint64_t SizeInBits, uint32_t AlignInBits, unsigned Encoding,
-              DIFlags Flags, ArrayRef<Metadata *> Ops)
+              uint32_t NumExtraInhabitants, DIFlags Flags,
+              ArrayRef<Metadata *> Ops)
       : DIType(C, DIBasicTypeKind, Storage, Tag, 0, SizeInBits, AlignInBits, 0,
-               Flags, Ops),
+               NumExtraInhabitants, Flags, Ops),
         Encoding(Encoding) {}
   ~DIBasicType() = default;
 
   static DIBasicType *getImpl(LLVMContext &Context, unsigned Tag,
                               StringRef Name, uint64_t SizeInBits,
                               uint32_t AlignInBits, unsigned Encoding,
-                              DIFlags Flags, StorageType Storage,
-                              bool ShouldCreate = true) {
+                              uint32_t NumExtraInhabitants, DIFlags Flags,
+                              StorageType Storage, bool ShouldCreate = true) {
     return getImpl(Context, Tag, getCanonicalMDString(Context, Name),
-                   SizeInBits, AlignInBits, Encoding, Flags, Storage,
-                   ShouldCreate);
+                   SizeInBits, AlignInBits, Encoding, NumExtraInhabitants,
+                   Flags, Storage, ShouldCreate);
   }
   static DIBasicType *getImpl(LLVMContext &Context, unsigned Tag,
                               MDString *Name, uint64_t SizeInBits,
                               uint32_t AlignInBits, unsigned Encoding,
-                              DIFlags Flags, StorageType Storage,
-                              bool ShouldCreate = true);
+                              uint32_t NumExtraInhabitants, DIFlags Flags,
+                              StorageType Storage, bool ShouldCreate = true);
 
   TempDIBasicType cloneImpl() const {
     return getTemporary(getContext(), getTag(), getName(), getSizeInBits(),
-                        getAlignInBits(), getEncoding(), getFlags());
+                        getAlignInBits(), getEncoding(),
+                        getNumExtraInhabitants(), getFlags());
   }
 
 public:
   DEFINE_MDNODE_GET(DIBasicType, (unsigned Tag, StringRef Name),
-                    (Tag, Name, 0, 0, 0, FlagZero))
+                    (Tag, Name, 0, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, StringRef Name, uint64_t SizeInBits),
-                    (Tag, Name, SizeInBits, 0, 0, FlagZero))
+                    (Tag, Name, SizeInBits, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, MDString *Name, uint64_t SizeInBits),
-                    (Tag, Name, SizeInBits, 0, 0, FlagZero))
+                    (Tag, Name, SizeInBits, 0, 0, 0, FlagZero))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, StringRef Name, uint64_t SizeInBits,
-                     uint32_t AlignInBits, unsigned Encoding, DIFlags Flags),
-                    (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags))
+                     uint32_t AlignInBits, unsigned Encoding,
+                     uint32_t NumExtraInhabitants, DIFlags Flags),
+                    (Tag, Name, SizeInBits, AlignInBits, Encoding,
+                     NumExtraInhabitants, Flags))
   DEFINE_MDNODE_GET(DIBasicType,
                     (unsigned Tag, MDString *Name, uint64_t SizeInBits,
-                     uint32_t AlignInBits, unsigned Encoding, DIFlags Flags),
-                    (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags))
+                     uint32_t AlignInBits, unsigned Encoding,
+                     uint32_t NumExtraInhabitants, DIFlags Flags),
+                    (Tag, Name, SizeInBits, AlignInBits, Encoding,
+                     NumExtraInhabitants, Flags))
 
   TempDIBasicType clone() const { return cloneImpl(); }
 
@@ -890,7 +904,7 @@ class DIStringType : public DIType {
                uint64_t SizeInBits, uint32_t AlignInBits, unsigned Encoding,
                ArrayRef<Metadata *> Ops)
       : DIType(C, DIStringTypeKind, Storage, Tag, 0, SizeInBits, AlignInBits, 0,
-               FlagZero, Ops),
+               0, FlagZero, Ops),
         Encoding(Encoding) {}
   ~DIStringType() = default;
 
@@ -1016,7 +1030,7 @@ class DIDerivedType : public DIType {
                 std::optional<PtrAuthData> PtrAuthData, DIFlags Flags,
                 ArrayRef<Metadata *> Ops)
       : DIType(C, DIDerivedTypeKind, Storage, Tag, Line, SizeInBits,
-               AlignInBits, OffsetInBits, Flags, Ops),
+               AlignInBits, OffsetInBits, 0, Flags, Ops),
         DWARFAddressSpace(DWARFAddressSpace) {
     if (PtrAuthData)
       SubclassData32 = PtrAuthData->RawData;
@@ -1157,39 +1171,43 @@ class DICompositeType : public DIType {
 
   DICompositeType(LLVMContext &C, StorageType Storage, unsigned Tag,
                   unsigned Line, unsigned RuntimeLang, uint64_t SizeInBits,
-                  uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags,
+                  uint32_t AlignInBits, uint64_t OffsetInBits,
+                  uint32_t NumExtraInhabitants, DIFlags Flags,
                   ArrayRef<Metadata *> Ops)
       : DIType(C, DICompositeTypeKind, Storage, Tag, Line, SizeInBits,
-               AlignInBits, OffsetInBits, Flags, Ops),
+               AlignInBits, OffsetInBits, NumExtraInhabitants, Flags, Ops),
         RuntimeLang(RuntimeLang) {}
   ~DICompositeType() = default;
 
   /// Change fields in place.
   void mutate(unsigned Tag, unsigned Line, unsigned RuntimeLang,
               uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
-              DIFlags Flags) {
+              uint32_t NumExtraInhabitants, DIFlags Flags) {
     assert(isDistinct() && "Only distinct nodes can mutate");
     assert(getRawIdentifier() && "Only ODR-uniqued nodes should mutate");
     this->RuntimeLang = RuntimeLang;
-    DIType::mutate(Tag, Line, SizeInBits, AlignInBits, OffsetInBits, Flags);
+    DIType::mutate(Tag, Line, SizeInBits, AlignInBits, OffsetInBits,
+                   NumExtraInhabitants, Flags);
   }
 
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, StringRef Name, Metadata *File,
           unsigned Line, DIScope *Scope, DIType *BaseType, uint64_t SizeInBits,
-          uint32_t AlignInBits, uint64_t OffsetInBits, DIFlags Flags,
-          DINodeArray Elements, unsigned RuntimeLang, DIType *VTableHolder,
+          uint32_t AlignInBits, uint64_t OffsetInBits,
+          uint32_t NumExtraInhabitants, DIFlags Flags, DINodeArray Elements,
+          unsigned RuntimeLang, DIType *VTableHolder,
           DITemplateParameterArray TemplateParams, StringRef Identifier,
           DIDerivedType *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
           DINodeArray Annotations, StorageType Storage,
           bool ShouldCreate = true) {
-    return getImpl(
-        Context, Tag, getCanonicalMDString(Context, Name), File, Line, Scope,
-        BaseType, SizeInBits, AlignInBits, OffsetInBits, Flags, Elements.get(),
-        RuntimeLang, VTableHolder, TemplateParams.get(),
-        getCanonicalMDString(Context, Identifier), Discriminator, DataLocation,
-        Associated, Allocated, Rank, Annotations.get(), Storage, ShouldCreate);
+    return getImpl(Context, Tag, getCanonicalMDString(Context, Name), File,
+                   Line, Scope, BaseType, SizeInBits, AlignInBits, OffsetInBits,
+                   Flags, Elements.get(), RuntimeLang, VTableHolder,
+                   TemplateParams.get(),
+                   getCanonicalMDString(Context, Identifier), Discriminator,
+                   DataLocation, Associated, Allocated, Rank, Annotations.get(),
+                   NumExtraInhabitants, Storage, ShouldCreate);
   }
   static DICompositeType *
   getImpl(LLVMContext &Context, unsigned Tag, MDString *Name, Metadata *File,
@@ -1199,7 +1217,8 @@ class DICompositeType : public DIType {
           Metadata *VTableHolder, Metadata *TemplateParams,
           MDString *Identifier, Metadata *Discriminator, Metadata *DataLocation,
           Metadata *Associated, Metadata *Allocated, Metadata *Rank,
-          Metadata *Annotations, StorageType Storage, bool ShouldCreate = true);
+          Metadata *Annotations, uint32_t NumExtraInhabitants,
+          StorageType Storage, bool ShouldCreate = true);
 
   TempDICompositeType cloneImpl() const {
     return getTemporary(
@@ -1208,7 +1227,7 @@ class DICompositeType : public DIType {
         getFlags(), getElements(), getRuntimeLang(), getVTableHolder(),
         getTemplateParams(), getIdentifier(), getDiscriminator(),
         getRawDataLocation(), getRawAssociated(), getRawAllocated(),
-        getRawRank(), getAnnotations());
+        getRawRank(), getAnnotations(), getNumExtraInhabitants());
   }
 
 public:
@@ -1222,11 +1241,11 @@ class DICompositeType : public DIType {
        StringRef Identifier = "", DIDerivedType *Discriminator = nullptr,
        Metadata *DataLocation = nullptr, Metadata *Associated = nullptr,
        Metadata *Allocated = nullptr, Metadata *Rank = nullptr,
-       DINodeArray Annotations = nullptr),
+       DINodeArray Annotations = nullptr, uint32_t NumExtraInhabitants = 0),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
-       OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
-       Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations))
+       OffsetInBits, NumExtraInhabitants, Flags, Elements, RuntimeLang,
+       VTableHolder, TemplateParams, Identifier, Discriminator, DataLocation,
+       Associated, Allocated, Rank, Annotations))
   DEFINE_MDNODE_GET(
       DICompositeType,
       (unsigned Tag, MDString *Name, Metadata *File, unsigned Line,
@@ -1236,11 +1255,12 @@ class DICompositeType : public DIType {
        Metadata *TemplateParams = nullptr, MDString *Identifier = nullptr,
        Metadata *Discriminator = nullptr, Metadata *DataLocation = nullptr,
        Metadata *Associated = nullptr, Metadata *Allocated = nullptr,
-       Metadata *Rank = nullptr, Metadata *Annotations = nullptr),
+       Metadata *Rank = nullptr, Metadata *Annotations = nullptr,
+       uint32_t NumExtraInhabitants = 0),
       (Tag, Name, File, Line, Scope, BaseType, SizeInBits, AlignInBits,
        OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder, TemplateParams,
        Identifier, Discriminator, DataLocation, Associated, Allocated, Rank,
-       Annotations))
+       Annotations, NumExtraInhabitants))
 
   TempDICompositeType clone() const { return cloneImpl(); }
 
@@ -1255,8 +1275,8 @@ class DICompositeType : public DIType {
   getODRType(LLVMContext &Context, MDString &Identifier, unsigned Tag,
              MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
              Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
-             uint64_t OffsetInBits, DIFlags Flags, Metadata *Elements,
-             unsigned RuntimeLang, Metadata *VTableHolder,
+             uint64_t OffsetInBits, uint32_t NumExtraInhabitants, DIFlags Flags,
+             Metadata *Elements, unsigned RuntimeLang, Metadata *VTableHolder,
              Metadata *TemplateParams, Metadata *Discriminator,
              Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
              Metadata *Rank, Metadata *Annotations);
@@ -1272,15 +1292,14 @@ class DICompositeType : public DIType {
   ///
   /// If not \a LLVMContext::isODRUniquingDebugTypes(), this function returns
   /// nullptr.
-  static DICompositeType *
-  buildODRType(LLVMContext &Context, MDString &Identifier, unsigned Tag,
-               MDString *Name, Metadata *File, unsigned Line, Metadata *Scope,
-               Metadata *BaseType, uint64_t SizeInBits, uint32_t AlignInBits,
-               uint64_t OffsetInBits, DIFlags Flags, Metadata *Elements,
-               unsigned RuntimeLang, Metadata *VTableHolder,
-               Metadata *TemplateParams, Metadata *Discriminator,
-               Metadata *DataLocation, Metadata *Associated,
-               Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
+  static DICompositeType *buildODRType(
+      LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
+      Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,
+      uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
+      uint32_t NumExtraInhabitants, DIFlags Flags, Metadata *Elements,
+      unsigned RuntimeLang, Metadata *VTableHolder, Metadata *TemplateParams,
+      Metadata *Discriminator, Metadata *DataLocation, Metadata *Associated,
+      Metadata *Allocated, Metadata *Rank, Metadata *Annotations);
 
   DIType *getBaseType() const { return cast_or_null<DIType>(getRawBaseType()); }
   DINodeArray getElements() const {
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 5b9bddeb7cfe82..af9155636a2239 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -5329,12 +5329,14 @@ bool LLParser::parseDIBasicType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(size, MDUnsignedField, (0, UINT64_MAX));                            \
   OPTIONAL(align, MDUnsignedField, (0, UINT32_MAX));                           \
   OPTIONAL(encoding, DwarfAttEncodingField, );                                 \
+  OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           \
   OPTIONAL(flags, DIFlagField, );
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
   Result = GET_OR_DISTINCT(DIBasicType, (Context, tag.Val, name.Val, size.Val,
-                                         align.Val, encoding.Val, flags.Val));
+                                         align.Val, encoding.Val,
+                                         num_extra_inhabitants.Val, flags.Val));
   return false;
 }
 
@@ -5432,7 +5434,8 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(associated, MDField, );                                             \
   OPTIONAL(allocated, MDField, );                                              \
   OPTIONAL(rank, MDSignedOrMDField, );                                         \
-  OPTIONAL(annotations, MDField, );
+  OPTIONAL(annotations, MDField, );                                            \
+  OPTIONAL(num_extra_inhabitants, MDUnsignedField, (0, UINT32_MAX));           
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
@@ -5447,10 +5450,11 @@ bool LLParser::parseDICompositeType(MDNode *&Result, bool IsDistinct) {
   if (identifier.Val)
     if (auto *CT = DICompositeType::buildODRType(
             Context, *identifier.Val, tag.Val, name.Val, file.Val, line.Val,
-            scope.Val, baseType.Val, size.Val, align.Val, offset.Val, flags.Val,
-            elements.Val, runtimeLang.Val, vtableHolder.Val, templateParams.Val,
-            discriminator.Val, dataLocation.Val, associated.Val, allocated.Val,
-            Rank, annotations.Val)) {
+            scope.Val, baseType.Val, size.Val, align.Val, offset.Val,
+            num_extra_inhabitants.Val, flags.Val, elements.Val, runtimeLang.Val,
+            vtableHolder.Val, templateParams.Val, discriminator.Val,
+            dataLocation.Val, asso...
[truncated]

github-actions · 2024-10-16T18:05:47Z

✅ With the latest revision this PR passed the C/C++ code formatter.

pogo59

A count of invalid bit patterns doesn't seem that helpful to the debugger. What would it do with this information? How would it know what the actual invalid bit patterns are? For example, an enum with two enumerators with values equal to 0 and 5 would have exactly the same number of "extra inhabitants" as bool.

llvm/test/DebugInfo/AArch64/num_extra_inhabitants.ll

augusto2112 · 2024-10-16T22:06:38Z

What would it do with this information?

This information is used to calculate the layout of types. For example, since Bool has extra inhabitants, the debugger needs that information to calculate that Optional will only use 1 byte.

Since Swift generics are not monomorphized, by using dynamic libraries you can have generic types whose size, alignment, etc, are known only at runtime (which is why this feature is needed).

How would it know what the actual invalid bit patterns are? For example, an enum with two enumerators with values equal to 0 and 5 would have exactly the same number of "extra inhabitants" as bool.

This is part of the ABI of the language (which is why I added the attribute as an Apple extension). You are correct that if you have an enum with two enumerators equal to 0 and 5 you can't know which bit patterns are extra inhabitants. But for enums that don't specify what the integer representation is, two enumerators means that all bit patterns outside 0 and 1 are extra inhabitants.

dwblaikie · 2024-10-17T16:26:23Z

Can you include some of these details in the description/commit message?
(this bit, or something like it, especially: "Since Swift generics are not monomorphized, by using dynamic libraries you can have generic types whose size, alignment, etc, are known only at runtime (which is why this feature is needed).")

augusto2112 · 2024-10-17T17:39:13Z

Can you include some of these details in the description/commit message? (this bit, or something like it, especially: "Since Swift generics are not monomorphized, by using dynamic libraries you can have generic types whose size, alignment, etc, are known only at runtime (which is why this feature is needed).")

Ok, I updated the commit message.

dwblaikie · 2024-10-17T17:42:53Z

Oh, do you have a link to the ABI documentation that describes/shows how "num extra inhabitants" would be enough to know which bit patterns are available for extra inhabitants?

augusto2112 · 2024-10-17T17:52:27Z

Oh, do you have a link to the ABI documentation that describes/shows how "num extra inhabitants" would be enough to know which bit patterns are available for extra inhabitants?

There's some documentation at https://github.com/swiftlang/swift/blob/main/docs/ABIStabilityManifesto.md and https://github.com/swiftlang/swift/blob/main/docs/ABI/TypeLayout.rst, although it doesn't seem to be complete, unfortunately.

An extra inhabitant is a bit pattern that does not represent a valid value for instances of a given type. The number of extra inhabitants is the number of those bit configurations. This is used by Swift to save space when composing types. For example, because Bool only needs 2 bit patterns to represent all of its values (true and false), an Optional<Bool> only occupies 1 byte in memory by using a bit configuration that is unused by Bool. Which bit patterns are unused are part of the ABI of the language. Since Swift generics are not monomorphized, by using dynamic libraries you can have generic types whose size, alignment, etc, are known only at runtime (which is why this feature is needed). This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF as an Apple extension.

llvm/include/llvm/IR/DIBuilder.h

llvm/include/llvm/BinaryFormat/Dwarf.def

adrian-prantl · 2024-11-01T23:36:17Z

llvm/include/llvm/IR/DebugInfoMetadata.h

@@ -712,31 +712,38 @@ class DIType : public DIScope {
  DIFlags Flags;
  uint64_t SizeInBits;
  uint64_t OffsetInBits;
+  uint32_t NumExtraInhabitants;


Does the Swift frontend ever use the OffsetInBits? If not, we could store the extra inhabitants in there. (That would be an implementation detail of DIType and DIType would assert that you don't try to set both extra inhabitants and an offset).

For everything else (Bitcode, Interface, assembler) leave it as it.

Swift uses OffsetInBits for DIDerivedType but not for DIBasicType or DICompositeType. OffsetInBits is used by other compilers in DICompositeType though. I prototyped what you suggested here but I think it'd make things significantly more complex and error prone for little gain. For example, when printing a DICompositeType we wouldn't be able to know if the field is an offset or the number of extra inhabitants, unless we add a flag tracking that on DIType (or tracking that in DICompositeType and making getOffsetInBits virtual) which I think would defeat the purpose of sharing the field for both types...

An extra inhabitant is a bit pattern that does not represent a valid value for instances of a given type. The number of extra inhabitants is the number of those bit configurations. This is used by Swift to save space when composing types. For example, because Bool only needs 2 bit patterns to represent all of its values (true and false), an Optional<Bool> only occupies 1 byte in memory by using a bit configuration that is unused by Bool. Which bit patterns are unused are part of the ABI of the language. Since Swift generics are not monomorphized, by using dynamic libraries you can have generic types whose size, alignment, etc, are known only at runtime (which is why this feature is needed). This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF as an Apple extension. (cherry picked from commit f6617d6)

An extra inhabitant is a bit pattern that does not represent a valid value for instances of a given type. The number of extra inhabitants is the number of those bit configurations. This is used by Swift to save space when composing types. For example, because Bool only needs 2 bit patterns to represent all of its values (true and false), an Optional<Bool> only occupies 1 byte in memory by using a bit configuration that is unused by Bool. Which bit patterns are unused are part of the ABI of the language. Since Swift generics are not monomorphized, by using dynamic libraries you can have generic types whose size, alignment, etc, are known only at runtime (which is why this feature is needed). This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF as an Apple extension. (cherry picked from commit f6617d6) (cherry picked from commit cdc3876)

[Next][Cherry-pick][DebugInfo] Add num_extra_inhabitants to debug info (llvm#112590)

which ended up passing 0 for the Discriminator arg, Discriminator for the DataLocation arg, etc. The DICompositeType::get's new NumExtraInhabitants parameter is at the end, and has a default value, so no change in the caller is necessary. See comment on #112590

zmodem · 2024-11-08T10:00:54Z

llvm/lib/IR/DIBuilder.cpp

@@ -551,7 +555,7 @@ DIBuilder::createVariantPart(DIScope *Scope, StringRef Name, DIFile *File,
  auto *R = DICompositeType::get(
      VMContext, dwarf::DW_TAG_variant_part, Name, File, LineNumber,
      getNonCompileUnitScope(Scope), nullptr, SizeInBits, AlignInBits, 0, Flags,
-      Elements, 0, nullptr, nullptr, UniqueIdentifier, Discriminator);
+      Elements, 0, nullptr, nullptr, UniqueIdentifier, 0, Discriminator);


This looks wrong. DICompositeType::get takes the new NumExtraInhabitants parameter at the end. Your change is now passing 0 for Discriminator, Discriminator for the DataLocation parameter, etc. That broke rustc's test suite, see (parts of) https://crbug.com/377743159

Since DICompositeType::get's NumExtraInhabitants was added at the end, and with a default value, no change here is necessary.

I've followed up in 546066e

Thanks @zmodem

This happened previously too with a similar change to the ::get APIs. Wonder if it's worth doing something about this to catch these types of issues at compile time. E.g., using stronger types is my first instinct.

[Cherry-pick][DebugInfo] Add num_extra_inhabitants to debug info (llvm#112590)

which ended up passing 0 for the Discriminator arg, Discriminator for the DataLocation arg, etc. The DICompositeType::get's new NumExtraInhabitants parameter is at the end, and has a default value, so no change in the caller is necessary. See comment on llvm#112590

augusto2112 requested review from bulbazord and adrian-prantl October 16, 2024 18:02

llvmbot added debuginfo llvm:ir llvm:binary-utilities labels Oct 16, 2024

augusto2112 force-pushed the extra-inhabitant-deb branch from bef3e90 to afdd5be Compare October 16, 2024 20:29

pogo59 reviewed Oct 16, 2024

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llvm/test/DebugInfo/AArch64/num_extra_inhabitants.ll Show resolved Hide resolved

augusto2112 force-pushed the extra-inhabitant-deb branch from afdd5be to 8f01a60 Compare October 16, 2024 23:20

augusto2112 force-pushed the extra-inhabitant-deb branch from 8f01a60 to 0d8591a Compare October 17, 2024 17:38

augusto2112 force-pushed the extra-inhabitant-deb branch from 0d8591a to e335415 Compare October 17, 2024 17:43

augusto2112 requested review from felipepiovezan and JDevlieghere October 17, 2024 22:27

augusto2112 force-pushed the extra-inhabitant-deb branch from 0103ccf to 7db0516 Compare November 1, 2024 23:29

adrian-prantl reviewed Nov 1, 2024

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augusto2112 added 2 commits November 4, 2024 14:08

address comments

5684f83

Fix test

ef9a771

augusto2112 merged commit f6617d6 into llvm:main Nov 6, 2024
8 checks passed

augusto2112 added a commit to swiftlang/llvm-project that referenced this pull request Nov 7, 2024

Merge pull request #9536 from augusto2112/next-cp-down-stream-xi

43d9053

[Next][Cherry-pick][DebugInfo] Add num_extra_inhabitants to debug info (llvm#112590)

zmodem reviewed Nov 8, 2024

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augusto2112 added a commit to swiftlang/llvm-project that referenced this pull request Nov 8, 2024

Merge pull request #9534 from augusto2112/cp-down-stream-xi

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[Cherry-pick][DebugInfo] Add num_extra_inhabitants to debug info (llvm#112590)

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[DebugInfo] Add num_extra_inhabitants to debug info #112590

[DebugInfo] Add num_extra_inhabitants to debug info #112590

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[DebugInfo] Add num_extra_inhabitants to debug info #112590

[DebugInfo] Add num_extra_inhabitants to debug info #112590

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augusto2112 commented Oct 16, 2024 •

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