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[globalopt] Don't emit DWARF fragments for members 

of a struct that cover the whole struct

This can happen when the rest of the
members of are zero length. Following
the same pattern applied to the SROA
pass in:
d7f6f1636d

Fixes: https://bugs.llvm.org/show_bug.cgi?id=45335

Differential Revision: https://reviews.llvm.org/D78720
This commit is contained in:
David Spickett 2020-04-23 14:40:57 +01:00
parent 09f6b9792b
commit 3929429347
2 changed files with 79 additions and 6 deletions
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16
llvm/lib/Transforms/IPO/GlobalOpt.cpp
View File

@ -467,14 +467,19 @@ static bool CanDoGlobalSRA(GlobalVariable *GV) {
/// 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,
unsigned NumElements) {
uint64_t FragmentSizeInBits) {
SmallVector<DIGlobalVariableExpression *, 1> GVs;
GV->getDebugInfo(GVs);
for (auto *GVE : GVs) {
DIVariable *Var = GVE->getVariable();
Optional<uint64_t> VarSize = Var->getSizeInBits();
DIExpression *Expr = GVE->getExpression();
if (NumElements > 1) {
// If the FragmentSize is smaller than the variable,
// emit a fragment expression.
// If the variable size is unknown a fragment must be
// emitted to be safe.
if (!VarSize || FragmentSizeInBits < *VarSize) {
if (auto E = DIExpression::createFragmentExpression(
Expr, FragmentOffsetInBits, FragmentSizeInBits))
Expr = *E;
@ -556,8 +561,7 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
// Copy over the debug info for the variable.
uint64_t Size = DL.getTypeAllocSizeInBits(NGV->getValueType());
uint64_t FragmentOffsetInBits = Layout.getElementOffsetInBits(ElementIdx);
transferSRADebugInfo(GV, NGV, FragmentOffsetInBits, Size,
STy->getNumElements());
transferSRADebugInfo(GV, NGV, FragmentOffsetInBits, Size);
} else {
uint64_t EltSize = DL.getTypeAllocSize(ElTy);
Align EltAlign(DL.getABITypeAlignment(ElTy));
@ -570,7 +574,7 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
if (NewAlign > EltAlign)
NGV->setAlignment(NewAlign);
transferSRADebugInfo(GV, NGV, FragmentSizeInBits * ElementIdx,
FragmentSizeInBits, GetSRASequentialNumElements(Ty));
FragmentSizeInBits);
}
}

69
llvm/test/DebugInfo/Generic/global-sra-struct-zero-length.ll Normal file
View File

@ -0,0 +1,69 @@
; RUN: opt -S -globalopt < %s | FileCheck %s
; Generated at -O2 -g from:
; typedef struct {
; } a;
; static struct {
; long b;
; a c;
; } d;
; e() {
; long f = d.b + 1;
; d.b = f;
; }
; (with some simplification by hand)
; Check that the global variable "d" is not
; emitted as a fragment after the member "c"
; is removed.
; d.b is referenced, but d.c has zero length.
; So a fragment covering d.b would be the same
; size as d itself.
source_filename = "pr45335.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.anon = type { i64, %struct.a }
%struct.a = type {}
; CHECK: @d.0 = internal unnamed_addr global i64 0, align 8, !dbg ![[GVE:.*]]
@d = internal global %struct.anon zeroinitializer, align 8, !dbg !0
; Function Attrs: noinline nounwind uwtable
define dso_local i32 @e() #0 !dbg !18 {
entry:
%0 = load i64, i64* getelementptr inbounds (%struct.anon, %struct.anon* @d, i32 0, i32 0), align 8
%add = add nsw i64 %0, 1
call void @llvm.dbg.value(metadata i64 %add, metadata !24, metadata !DIExpression()), !dbg !25
store i64 %add, i64* getelementptr inbounds (%struct.anon, %struct.anon* @d, i32 0, i32 0), align 8
ret i32 undef
}
; Function Attrs: nounwind readnone speculatable willreturn
declare void @llvm.dbg.declare(metadata, metadata, metadata)
; Function Attrs: nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!14, !15}
; CHECK: ![[GVE]] = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "d", scope: !2, file: !3, line: 6, type: !7, isLocal: true, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !{}, globals: !{!0}, splitDebugInlining: false, nameTableKind: None)
!3 = !DIFile(filename: "pr45335.c", directory: "/")
!7 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !3, line: 3, size: 64, elements: !8)
!8 = !{!9, !11}
!9 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !7, file: !3, line: 4, baseType: !10, size: 64)
!10 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
!11 = !DIDerivedType(tag: DW_TAG_member, name: "c", scope: !7, file: !3, line: 5, baseType: !12, offset: 64)
!12 = !DIDerivedType(tag: DW_TAG_typedef, name: "a", file: !3, line: 2, baseType: !13)
!13 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !3, line: 1, elements: !{})
!14 = !{i32 7, !"Dwarf Version", i32 4}
!15 = !{i32 2, !"Debug Info Version", i32 3}
!18 = distinct !DISubprogram(name: "e", scope: !3, file: !3, line: 7, type: !19, scopeLine: 7, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !{})
!19 = !DISubroutineType(types: !{!21})
!21 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!24 = !DILocalVariable(name: "f", scope: !18, file: !3, line: 8, type: !10)
!25 = !DILocation(line: 0, scope: !18)