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[globalopt] Change so that emitting fragments doesn't use the type size of DIVariables

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When turning on -debug-info-kind=constructor we ran into a "fragment covers
entire variable" error during thinlto. The fragment is currently always
emitted if there is no type size, but sometimes the variable has a
forward declared struct type which doesn't have a size.

This changes the code to get the type size from the GlobalVariable instead.

Differential Revision: https://reviews.llvm.org/D85572
This commit is contained in:
Amy Huang 2020-08-11 14:50:56 -07:00
parent 88e8651c48
commit ae7dfdd3ba
2 changed files with 69 additions and 8 deletions
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14
lib/Transforms/IPO/GlobalOpt.cpp
View File

@ -468,19 +468,16 @@ 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) {
uint64_t FragmentSizeInBits,
uint64_t VarSize) {
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 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 (FragmentSizeInBits < VarSize) {
if (auto E = DIExpression::createFragmentExpression(
Expr, FragmentOffsetInBits, FragmentSizeInBits))
Expr = *E;
@ -505,6 +502,7 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
assert(GV->hasLocalLinkage());
Constant *Init = GV->getInitializer();
Type *Ty = Init->getType();
uint64_t VarSize = DL.getTypeSizeInBits(Ty);
std::map<unsigned, GlobalVariable *> NewGlobals;
@ -560,7 +558,7 @@ 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);
transferSRADebugInfo(GV, NGV, FragmentOffsetInBits, Size, VarSize);
} else {
uint64_t EltSize = DL.getTypeAllocSize(ElTy);
Align EltAlign = DL.getABITypeAlign(ElTy);
@ -573,7 +571,7 @@ static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) {
if (NewAlign > EltAlign)
NGV->setAlignment(NewAlign);
transferSRADebugInfo(GV, NGV, FragmentSizeInBits * ElementIdx,
FragmentSizeInBits);
FragmentSizeInBits, VarSize);
}
}

63
test/DebugInfo/Generic/global-sra-struct-fwd-decl.ll Normal file
View File

@ -0,0 +1,63 @@
; 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;
; }
; (IR is modified so that d's struct type is forward declared.)
; Check that the global variable "d" is not
; emitted as a fragment if its struct type is
; forward declared but d.c has zero length, so
; a fragment shouldn't be emitted.
source_filename = "t.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: "t.c", directory: "/")
!7 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !3, line: 3, flags: DIFlagFwdDecl)
!10 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
!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)