[llvm] r312196 - Don't add a fragment expression when GlobalSRA splits up a single-member struct
Adrian Prantl via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 31 10:38:52 PDT 2017
I decided against that variant because it would be marginally more expensive to extract the size from the debug info and this approach just reuses data we already have lying around.
-- adrian
> On Aug 31, 2017, at 9:57 AM, David Blaikie <dblaikie at gmail.com> wrote:
>
> Would it be better to measure the size and do this generally if the size is the same? Or would that not work/be harder?
>
> On Wed, Aug 30, 2017 at 5:07 PM Adrian Prantl via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
> Author: adrian
> Date: Wed Aug 30 17:06:18 2017
> New Revision: 312196
>
> URL: http://llvm.org/viewvc/llvm-project?rev=312196&view=rev <http://llvm.org/viewvc/llvm-project?rev=312196&view=rev>
> Log:
> Don't add a fragment expression when GlobalSRA splits up a single-member struct
>
> Fixes PR34390.
>
> https://bugs.llvm.org/show_bug.cgi?id=34390 <https://bugs.llvm.org/show_bug.cgi?id=34390>
>
> Added:
> llvm/trunk/test/DebugInfo/Generic/global-sra-single-member.ll
> Modified:
> llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
>
> Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=312196&r1=312195&r2=312196&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=312196&r1=312195&r2=312196&view=diff>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Wed Aug 30 17:06:18 2017
> @@ -420,15 +420,17 @@ static bool GlobalUsersSafeToSRA(GlobalV
> /// Copy over the debug info for a variable to its SRA replacements.
> static void transferSRADebugInfo(GlobalVariable *GV, GlobalVariable *NGV,
> uint64_t FragmentOffsetInBits,
> - uint64_t FragmentSizeInBits) {
> + uint64_t FragmentSizeInBits,
> + unsigned NumElements) {
> SmallVector<DIGlobalVariableExpression *, 1> GVs;
> GV->getDebugInfo(GVs);
> for (auto *GVE : GVs) {
> DIVariable *Var = GVE->getVariable();
> DIExpression *Expr = GVE->getExpression();
> - auto *NExpr = DIExpression::createFragmentExpression(
> - Expr, FragmentOffsetInBits, FragmentSizeInBits);
> - auto *NGVE = DIGlobalVariableExpression::get(GVE->getContext(), Var, NExpr);
> + if (NumElements > 1)
> + Expr = DIExpression::createFragmentExpression(Expr, FragmentOffsetInBits,
> + FragmentSizeInBits);
> + auto *NGVE = DIGlobalVariableExpression::get(GVE->getContext(), Var, Expr);
> NGV->addDebugInfo(NGVE);
> }
> }
> @@ -458,9 +460,10 @@ static GlobalVariable *SRAGlobal(GlobalV
>
> if (StructType *STy = dyn_cast<StructType>(Ty)) {
> uint64_t FragmentOffset = 0;
> - NewGlobals.reserve(STy->getNumElements());
> + unsigned NumElements = STy->getNumElements();
> + NewGlobals.reserve(NumElements);
> const StructLayout &Layout = *DL.getStructLayout(STy);
> - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
> + for (unsigned i = 0, e = NumElements; i != e; ++i) {
> Constant *In = Init->getAggregateElement(i);
> assert(In && "Couldn't get element of initializer?");
> GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
> @@ -484,7 +487,7 @@ static GlobalVariable *SRAGlobal(GlobalV
> // Copy over the debug info for the variable.
> FragmentOffset = alignTo(FragmentOffset, NewAlign);
> uint64_t Size = DL.getTypeSizeInBits(NGV->getValueType());
> - transferSRADebugInfo(GV, NGV, FragmentOffset, Size);
> + transferSRADebugInfo(GV, NGV, FragmentOffset, Size, NumElements);
> FragmentOffset += Size;
> }
> } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
> @@ -516,8 +519,8 @@ static GlobalVariable *SRAGlobal(GlobalV
> unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
> if (NewAlign > EltAlign)
> NGV->setAlignment(NewAlign);
> -
> - transferSRADebugInfo(GV, NGV, FragmentSizeInBits * i, FragmentSizeInBits);
> + transferSRADebugInfo(GV, NGV, FragmentSizeInBits * i, FragmentSizeInBits,
> + NumElements);
> }
> }
>
>
> Added: llvm/trunk/test/DebugInfo/Generic/global-sra-single-member.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Generic/global-sra-single-member.ll?rev=312196&view=auto <http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Generic/global-sra-single-member.ll?rev=312196&view=auto>
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/Generic/global-sra-single-member.ll (added)
> +++ llvm/trunk/test/DebugInfo/Generic/global-sra-single-member.ll Wed Aug 30 17:06:18 2017
> @@ -0,0 +1,53 @@
> +; RUN: opt -S -globalopt < %s | FileCheck %s
> +; struct {
> +; int f0;
> +; } static a;
> +; int main() {
> +; a.f0++;
> +; return 0;
> +; }
> +
> +source_filename = "pr34390.c"
> +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-apple-macosx10.12.0"
> +
> +%struct.anon = type { i32 }
> +
> +; CHECK: @a.0 = internal unnamed_addr global i32 0, align 4, !dbg ![[GVE:.*]]
> + at a = internal global %struct.anon zeroinitializer, align 4, !dbg !0
> +
> +define i32 @main() #0 !dbg !15 {
> +entry:
> + %retval = alloca i32, align 4
> + store i32 0, i32* %retval, align 4
> + %0 = load i32, i32* getelementptr inbounds (%struct.anon, %struct.anon* @a, i32 0, i32 0), align 4, !dbg !18
> + %inc = add nsw i32 %0, 1, !dbg !18
> + store i32 %inc, i32* getelementptr inbounds (%struct.anon, %struct.anon* @a, i32 0, i32 0), align 4, !dbg !18
> + ret i32 0, !dbg !19
> +}
> +
> +attributes #0 = { noinline nounwind optnone ssp uwtable }
> +
> +!llvm.dbg.cu <http://llvm.dbg.cu/> = !{!2}
> +!llvm.module.flags = !{!10, !11, !12, !13}
> +
> +; CHECK: ![[GVE]] = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
> +!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
> +!1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 3, type: !6, isLocal: true, isDefinition: true)
> +!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 (trunk 312175) (llvm/trunk 312146)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
> +!3 = !DIFile(filename: "test.c", directory: "/")
> +!4 = !{}
> +!5 = !{!0}
> +!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !3, line: 1, size: 32, elements: !7)
> +!7 = !{!8}
> +!8 = !DIDerivedType(tag: DW_TAG_member, name: "f0", scope: !6, file: !3, line: 2, baseType: !9, size: 32)
> +!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> +!10 = !{i32 2, !"Dwarf Version", i32 4}
> +!11 = !{i32 2, !"Debug Info Version", i32 3}
> +!12 = !{i32 1, !"wchar_size", i32 4}
> +!13 = !{i32 7, !"PIC Level", i32 2}
> +!15 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 4, type: !16, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: false, unit: !2, variables: !4)
> +!16 = !DISubroutineType(types: !17)
> +!17 = !{!9}
> +!18 = !DILocation(line: 5, column: 7, scope: !15)
> +!19 = !DILocation(line: 6, column: 3, scope: !15)
>
>
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