[flang][debug] Don't generate debug for compiler-generated variables

[abidh]

Flang generates many globals to handle derived types. There was a check in debug info to filter them based on the information that their names start with a period. This changed since PR#104859 where 'X' is being used instead of '.'.

This PR fixes this issue by also adding 'X' in that list. As user variables gets lower cased by the NameUniquer, there is no risk that those will be filtered out. I added a test for that to be sure.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

Author: Abid Qadeer (abidh)

Changes

Flang generates many globals to handle derived types. There was a check in debug info to filter them based on the information that their names start with a period. This changed since PR#104859 where 'X' is being used instead of '.'.

This PR fixes this issue by also adding 'X' in that list. As user variables gets lower cased by the NameUniquer, there is no risk that those will be filtered out. I added a test for that to be sure.

---

Full diff: https://github.com/llvm/llvm-project/pull/112423.diff

4 Files Affected:

• (modified) flang/lib/Optimizer/Transforms/AddDebugInfo.cpp (+7-4)
• (added) flang/test/Integration/debug-extra-global.f90 (+14)
• (modified) flang/test/Transforms/debug-derived-type-1.fir (+5-5)
• (added) flang/test/Transforms/debug-extra-global.fir (+18)

diff --git a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
index 400a8648dd7e07..f31c86cf678635 100644
--- a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
+++ b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
@@ -211,10 +211,13 @@ void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
   if (result.first != fir::NameUniquer::NameKind::VARIABLE)
     return;
 
-  // Discard entries that describe a derived type. Usually start with '.c.',
-  // '.dt.' or '.n.'. It would be better if result of the deconstruct had a flag
-  // for such values so that we dont have to look at string values.
-  if (!result.second.name.empty() && result.second.name[0] == '.')
+  // Discard entries that describe a derived type. They start with either '.' or
+  // 'X'. We filter both of them out. Note that NameUniquer makes the name lower
+  // case so user variables should be safe. It would be better if result of the
+  // deconstruct had a flag for such values so that we dont have to look at
+  // string values.
+  if (!result.second.name.empty() &&
+      (result.second.name[0] == '.' || result.second.name[0] == 'X'))
     return;
 
   unsigned line = getLineFromLoc(globalOp.getLoc());
diff --git a/flang/test/Integration/debug-extra-global.f90 b/flang/test/Integration/debug-extra-global.f90
new file mode 100644
index 00000000000000..c0ad2e306386da
--- /dev/null
+++ b/flang/test/Integration/debug-extra-global.f90
@@ -0,0 +1,14 @@
+! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck  %s
+
+program test
+ type t1
+   integer :: XcX
+   integer :: xdtx
+ end type
+  type(t1) :: var
+  var%XcX = 2
+  var%xdtx = 3
+end
+
+! Test that there is no debug info for compiler generated globals.
+! CHECK-NOT: DIGlobalVariable
diff --git a/flang/test/Transforms/debug-derived-type-1.fir b/flang/test/Transforms/debug-derived-type-1.fir
index cfbd361a91e726..b1c6076c9c212a 100644
--- a/flang/test/Transforms/debug-derived-type-1.fir
+++ b/flang/test/Transforms/debug-derived-type-1.fir
@@ -8,15 +8,15 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<!llvm.ptr<272>, d
     %0 = fir.zero_bits !fir.type<_QMm_employeeTt_employee{t_person:!fir.type<_QMm_employeeTt_person{t_address:!fir.type<_QMm_employeeTt_address{house_number:i32}>,name:!fir.char<1,20>}>,hired_date:!fir.type<_QMm_employeeTt_date{year:i32,month:i32,day:i32}>,monthly_salary:f32}>
     fir.has_value %0 : !fir.type<_QMm_employeeTt_employee{t_person:!fir.type<_QMm_employeeTt_person{t_address:!fir.type<_QMm_employeeTt_address{house_number:i32}>,name:!fir.char<1,20>}>,hired_date:!fir.type<_QMm_employeeTt_date{year:i32,month:i32,day:i32}>,monthly_salary:f32}>
   } loc(#loc5)
-  fir.global @_QMt1Evar : !fir.type<_QMt1Tt_t1{age:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}> {
-    %0 = fir.zero_bits !fir.type<_QMt1Tt_t1{age:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}>
-    fir.has_value %0 : !fir.type<_QMt1Tt_t1{age:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}>
+  fir.global @_QMt1Evar : !fir.type<_QMt1Tt_t1{XcX:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}> {
+    %0 = fir.zero_bits !fir.type<_QMt1Tt_t1{XcX:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}>
+    fir.has_value %0 : !fir.type<_QMt1Tt_t1{XcX:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}>
   } loc(#loc6)
   fir.global @_QMtest_1Exyz : !fir.type<_QMtest_1Tsometype{m_array:!fir.array<3xi32>,m_vt1:!fir.box<!fir.heap<!fir.type<_QMtest_1Tt1{name:!fir.char<1,20>,height:f32}>>>,v2:i32,m_alloc:!fir.box<!fir.heap<!fir.array<?xi32>>>,v3:i32,m_first:!fir.box<!fir.heap<!fir.char<1,?>>>,v4:i32,m_p1:!fir.box<!fir.ptr<i32>>,v5:i32,m_p2:!fir.box<!fir.ptr<i32>>,v6:i32,m_p3:!fir.box<!fir.ptr<!fir.array<?xi32>>>,v7:i32}> {
     %0 = fir.zero_bits !fir.type<_QMtest_1Tsometype{m_array:!fir.array<3xi32>,m_vt1:!fir.box<!fir.heap<!fir.type<_QMtest_1Tt1{name:!fir.char<1,20>,height:f32}>>>,v2:i32,m_alloc:!fir.box<!fir.heap<!fir.array<?xi32>>>,v3:i32,m_first:!fir.box<!fir.heap<!fir.char<1,?>>>,v4:i32,m_p1:!fir.box<!fir.ptr<i32>>,v5:i32,m_p2:!fir.box<!fir.ptr<i32>>,v6:i32,m_p3:!fir.box<!fir.ptr<!fir.array<?xi32>>>,v7:i32}>
     fir.has_value %0 : !fir.type<_QMtest_1Tsometype{m_array:!fir.array<3xi32>,m_vt1:!fir.box<!fir.heap<!fir.type<_QMtest_1Tt1{name:!fir.char<1,20>,height:f32}>>>,v2:i32,m_alloc:!fir.box<!fir.heap<!fir.array<?xi32>>>,v3:i32,m_first:!fir.box<!fir.heap<!fir.char<1,?>>>,v4:i32,m_p1:!fir.box<!fir.ptr<i32>>,v5:i32,m_p2:!fir.box<!fir.ptr<i32>>,v6:i32,m_p3:!fir.box<!fir.ptr<!fir.array<?xi32>>>,v7:i32}>
   } loc(#loc12)
-  fir.type_info @_QMt1Tt_t1 noinit nodestroy nofinal : !fir.type<_QMt1Tt_t1{age:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}> loc(#loc7)
+  fir.type_info @_QMt1Tt_t1 noinit nodestroy nofinal : !fir.type<_QMt1Tt_t1{XcX:i32,points:!fir.array<3xcomplex<f32>>,cond:!fir.logical<1>,name:!fir.char<1,20>,ratio:f64}> loc(#loc7)
   fir.type_info @_QMm_employeeTt_address noinit nodestroy nofinal : !fir.type<_QMm_employeeTt_address{house_number:i32}> loc(#loc1)
   fir.type_info @_QMm_employeeTt_person noinit nodestroy nofinal extends !fir.type<_QMm_employeeTt_address{house_number:i32}> : !fir.type<_QMm_employeeTt_person{t_address:!fir.type<_QMm_employeeTt_address{house_number:i32}>,name:!fir.char<1,20>}> loc(#loc2)
   fir.type_info @_QMm_employeeTt_date noinit nodestroy nofinal : !fir.type<_QMm_employeeTt_date{year:i32,month:i32,day:i32}> loc(#loc3)
@@ -68,7 +68,7 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<!llvm.ptr<272>, d
 // CHECK-DAG: #[[ELME3:.*]] = #llvm.di_derived_type<tag = DW_TAG_member, name = "monthly_salary", baseType = #[[REAL4_TY]], sizeInBits = 32, alignInBits = 32, offsetInBits = 288>
 // CHECK-DAG: #[[EMP:.*]] = #llvm.di_composite_type<{{.*}}tag = DW_TAG_structure_type, name = "t_employee"{{.*}}line = 46, scope = #[[MOD]], sizeInBits = 320, elements = #[[ELME1]], #[[ELME2]], #[[ELME3]]>
 
-// CHECK-DAG: #[[ELM1:.*]] = #llvm.di_derived_type<tag = DW_TAG_member, name = "age", baseType = #[[INT_TY]], sizeInBits = 32, alignInBits = 32>
+// CHECK-DAG: #[[ELM1:.*]] = #llvm.di_derived_type<tag = DW_TAG_member, name = "XcX", baseType = #[[INT_TY]], sizeInBits = 32, alignInBits = 32>
 // CHECK-DAG: #[[ELM2:.*]] = #llvm.di_derived_type<tag = DW_TAG_member, name = "points", baseType = #[[CMX_ARR]], sizeInBits = 192, alignInBits = 32, offsetInBits = 32>
 // CHECK-DAG: #[[ELM3:.*]] = #llvm.di_derived_type<tag = DW_TAG_member, name = "cond", baseType = #[[LOG_TY]], sizeInBits = 8, alignInBits = 8, offsetInBits = 224>
 // CHECK-DAG: #[[ELM4:.*]] = #llvm.di_derived_type<tag = DW_TAG_member, name = "name", baseType = #[[STR_TY]], sizeInBits = 160, alignInBits = 8, offsetInBits = 232>
diff --git a/flang/test/Transforms/debug-extra-global.fir b/flang/test/Transforms/debug-extra-global.fir
new file mode 100644
index 00000000000000..d3bc22ad0c59b0
--- /dev/null
+++ b/flang/test/Transforms/debug-extra-global.fir
@@ -0,0 +1,18 @@
+// RUN: fir-opt --add-debug-info --mlir-print-debuginfo %s | FileCheck %s
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
+  fir.global linkonce_odr @_QFEXnXxcx constant target : !fir.char<1,3> {
+    %0 = fir.string_lit "xcx"(3) : !fir.char<1,3>
+    fir.has_value %0 : !fir.char<1,3>
+  } loc(#loc1)
+  fir.global linkonce_odr @_QFEXnXxdtx constant target : !fir.char<1,4> {
+    %0 = fir.string_lit "xdtx"(4) : !fir.char<1,4>
+    fir.has_value %0 : !fir.char<1,4>
+  } loc(#loc1)
+}
+#loc1 = loc("derived.f90":24:1)
+
+// Test that no di_global_variable gets created for these compile generated
+// globals.
+
+// CHECK-NOT: #di_global_variable

[jeanPerier]

nit inlined, LGTM otherwise.

[jeanPerier]

Please move the result.second.name[0] == '.' || result.second.name[0] == 'X' part into some static fir::NameUniquer::isSpecialSymbol(llvm::StringRef name) helper in Optimizer/Support/InternalNames so that the usages of these delimiters are better centralized and advertise.

Long term, it may be better to have some compiler generated flag attributes on the global/declare for such variables (and others) rather than relying on the names.
In semantics, these variables are tagged with the CompilerCreated symbol attribute, but it is currently not represented in FIR.

[abidh]

Thanks for the suggestion. I have moved the code into a separate function.

[jeanPerier]

Suggested change

	CHECK: !DIGlobalVariable(name: "xcx", linkageName: "_QMmExcx"{{.*}})
	! CHECK: !DIGlobalVariable(name: "xcx", linkageName: "_QMmExcx"{{.*}})

[abidh]

Thanks for catching this. Fixed.

[jeanPerier]

Thanks for the update