[GlobalOpt] Fix global SRA incorrect alignment on some elements (#115328

)

The logic had a flaw where the alignment from the original aggregate is
unintentionally retained for elements when the calculated known
alignment is not higher than the element's ABI type alignment.

Fixes #115282.

llvm/lib/Transforms/IPO/GlobalOpt.cpp

@@ -575,15 +575,16 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
         *GV->getParent(), Ty, false, GlobalVariable::InternalLinkage,
         Initializer, GV->getName() + "." + Twine(NameSuffix++), GV,
         GV->getThreadLocalMode(), GV->getAddressSpace());
+    // Start out by copying attributes from the original, including alignment.
     NGV->copyAttributesFrom(GV);
     NewGlobals.insert({OffsetForTy, NGV});
 
     // Calculate the known alignment of the field.  If the original aggregate
-    // had 256 byte alignment for example, something might depend on that:
+    // had 256 byte alignment for example, then the element at a given offset
+    // may also have a known alignment, and something might depend on that:
     // propagate info to each field.
     Align NewAlign = commonAlignment(StartAlignment, OffsetForTy);
-    if (NewAlign > DL.getABITypeAlign(Ty))
-      NGV->setAlignment(NewAlign);
+    NGV->setAlignment(NewAlign);
 
     // Copy over the debug info for the variable.
     transferSRADebugInfo(GV, NGV, OffsetForTy * 8,

llvm/test/DebugInfo/X86/global-sra-struct-fit-segment.ll

@@ -20,7 +20,7 @@
 %struct.BSS1 = type <{ [12 x i8] }>
 
 ;CHECK: @.BSS1.0 = internal unnamed_addr global i32 0, align 32, !dbg ![[GVE1:.*]]
-;CHECK: @.BSS1.1 = internal unnamed_addr global i32 0, align 32, !dbg ![[GVE2:.*]], !dbg ![[GVE4:.*]]
+;CHECK: @.BSS1.1 = internal unnamed_addr global i32 0, align 4, !dbg ![[GVE2:.*]], !dbg ![[GVE4:.*]]
 ;CHECK: @.BSS1.2 = internal unnamed_addr global i32 0, align 8, !dbg ![[GVE3:.*]]
 
 @.BSS1 = internal global %struct.BSS1 zeroinitializer, align 32, !dbg !0, !dbg !7, !dbg !10, !dbg !27, !dbg !29

llvm/test/DebugInfo/X86/global-sra-struct-part-overlap-segment.ll

@@ -26,7 +26,7 @@
 
 @.BSS3 = internal unnamed_addr global %struct.BSS3 zeroinitializer, align 32, !dbg !0, !dbg !7, !dbg !29
 ;CHECK: @.BSS3.0 = internal unnamed_addr global double 0.000000e+00, align 32, !dbg ![[GVE1:.*]], !dbg ![[GVE2:.*]]
-;CHECK: @.BSS3.1 = internal unnamed_addr global double 0.000000e+00, align 32, !dbg ![[GVE3:.*]], !dbg ![[GVE4:.*]], !dbg ![[GVE6:.*]]
+;CHECK: @.BSS3.1 = internal unnamed_addr global double 0.000000e+00, align 8, !dbg ![[GVE3:.*]], !dbg ![[GVE4:.*]], !dbg ![[GVE6:.*]]
 ;CHECK: @.BSS3.2 = internal unnamed_addr global double 0.000000e+00, align 16, !dbg ![[GVE5:.*]]
 
 @.C363_mymod_bar_ = internal constant [2 x i8] c"IF"

llvm/test/Transforms/GlobalOpt/globalsra-align.ll

@@ -15,9 +15,9 @@ target datalayout = "p:16:32:64" ; 16-bit pointers with 32-bit ABI alignment and
 
 ;.
 ; CHECK: @[[A_4:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 8
-; CHECK: @[[A_5:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 16
+; CHECK: @[[A_5:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 8
 ; CHECK: @[[A_6:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 16
-; CHECK: @[[A_7:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 16
+; CHECK: @[[A_7:[a-zA-Z0-9_$"\\.-]+]] = internal unnamed_addr externally_initialized global ptr null, align 8
 ;.
 define ptr @reduce_align_0() {
 ; CHECK-LABEL: @reduce_align_0(
@@ -31,7 +31,7 @@ define ptr @reduce_align_0() {
 
 define ptr @reduce_align_1() {
 ; CHECK-LABEL: @reduce_align_1(
-; CHECK-NEXT:    [[X:%.*]] = load ptr, ptr @a.5, align 16
+; CHECK-NEXT:    [[X:%.*]] = load ptr, ptr @a.5, align 8
 ; CHECK-NEXT:    ret ptr [[X]]
 ;
   %x = load ptr, ptr getelementptr inbounds ([3 x [7 x ptr]], ptr @a, i64 0, i64 2, i64 1), align 4
@@ -51,7 +51,7 @@ define ptr @reduce_align_2() {
 
 define ptr @reduce_align_3() {
 ; CHECK-LABEL: @reduce_align_3(
-; CHECK-NEXT:    [[X:%.*]] = load ptr, ptr @a.7, align 16
+; CHECK-NEXT:    [[X:%.*]] = load ptr, ptr @a.7, align 8
 ; CHECK-NEXT:    ret ptr [[X]]
 ;
   %x = load ptr, ptr getelementptr inbounds ([3 x [7 x ptr]], ptr @a, i64 0, i64 2, i64 3), align 4

llvm/test/Transforms/GlobalOpt/pr115282.ll

@@ -0,0 +1,51 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; RUN: opt < %s -passes=globalopt -S | FileCheck %s
+
+@params = internal global [4 x i32] zeroinitializer, align 32
+
+;.
+; CHECK: @params.0 = internal unnamed_addr global i32 0, align 32
+; CHECK: @params.1 = internal unnamed_addr global i32 0, align 4
+; CHECK: @params.2 = internal unnamed_addr global i32 0, align 8
+; CHECK: @params.3 = internal unnamed_addr global i32 0, align 4
+;.
+define void @set(i32 %a, i32 %b, i32 %c, i32 %d) {
+; CHECK-LABEL: define void @set(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]], i32 [[C:%.*]], i32 [[D:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:    store i32 [[A]], ptr @params.0, align 32
+; CHECK-NEXT:    store i32 [[B]], ptr @params.1, align 4
+; CHECK-NEXT:    store i32 [[C]], ptr @params.2, align 8
+; CHECK-NEXT:    store i32 [[D]], ptr @params.3, align 4
+; CHECK-NEXT:    ret void
+;
+  store i32 %a, ptr @params
+  store i32 %b, ptr getelementptr ([4 x i32], ptr @params, i32 0, i32 1)
+  store i32 %c, ptr getelementptr ([4 x i32], ptr @params, i32 0, i32 2)
+  store i32 %d, ptr getelementptr ([4 x i32], ptr @params, i32 0, i32 3)
+  ret void
+}
+
+%S = type { i32, i32, i32, i32 }
+
+define %S @get() {
+; CHECK-LABEL: define %S @get() local_unnamed_addr {
+; CHECK-NEXT:    [[A:%.*]] = load i32, ptr @params.0, align 32
+; CHECK-NEXT:    [[SA:%.*]] = insertvalue [[S:%.*]] undef, i32 [[A]], 0
+; CHECK-NEXT:    [[B:%.*]] = load i32, ptr @params.1, align 4
+; CHECK-NEXT:    [[SB:%.*]] = insertvalue [[S]] [[SA]], i32 [[B]], 1
+; CHECK-NEXT:    [[C:%.*]] = load i32, ptr @params.2, align 8
+; CHECK-NEXT:    [[SC:%.*]] = insertvalue [[S]] [[SB]], i32 [[C]], 2
+; CHECK-NEXT:    [[D:%.*]] = load i32, ptr @params.3, align 4
+; CHECK-NEXT:    [[SD:%.*]] = insertvalue [[S]] [[SC]], i32 [[D]], 3
+; CHECK-NEXT:    ret [[S]] [[SD]]
+;
+  %a = load i32, ptr @params
+  %sa = insertvalue %S undef, i32 %a, 0
+  %b = load i32, ptr getelementptr ([4 x i32], ptr @params, i32 0, i32 1)
+  %sb = insertvalue %S %sa, i32 %b, 1
+  %c = load i32, ptr getelementptr ([4 x i32], ptr @params, i32 0, i32 2)
+  %sc = insertvalue %S %sb, i32 %c, 2
+  %d = load i32, ptr getelementptr ([4 x i32], ptr @params, i32 0, i32 3)
+  %sd = insertvalue %S %sc, i32 %d, 3
+  ret %S %sd
+}