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[MemorySSA] Do not create memoryaccesses for debug info intrinsics.

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Summary:
Do not model debuginfo intrinsics in MemorySSA.
Regularly these are non-memory modifying instructions. With -disable-basicaa, they were being modelled as Defs.

Reviewers: george.burgess.iv

Subscribers: aprantl, Prazek, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67307

llvm-svn: 371565
This commit is contained in:
Alina Sbirlea 2019-09-10 22:35:27 +00:00
parent aac114ca14
commit f7b4022db1
2 changed files with 63 additions and 2 deletions
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11
llvm/lib/Analysis/MemorySSA.cpp
View File

@ -285,6 +285,11 @@ instructionClobbersQuery(const MemoryDef *MD, const MemoryLocation &UseLoc,
case Intrinsic::invariant_end:
case Intrinsic::assume:
return {false, NoAlias};
case Intrinsic::dbg_addr:
case Intrinsic::dbg_declare:
case Intrinsic::dbg_label:
case Intrinsic::dbg_value:
llvm_unreachable("debuginfo shouldn't have associated defs!");
default:
break;
}
@ -1725,11 +1730,13 @@ MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I,
AliasAnalysisType *AAP,
const MemoryUseOrDef *Template) {
// The assume intrinsic has a control dependency which we model by claiming
// that it writes arbitrarily. Ignore that fake memory dependency here.
// that it writes arbitrarily. Debuginfo intrinsics may be considered
// clobbers when we have a nonstandard AA pipeline. Ignore these fake memory
// dependencies here.
// FIXME: Replace this special casing with a more accurate modelling of
// assume's control dependency.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
if (II->getIntrinsicID() == Intrinsic::assume)
if (II->getIntrinsicID() == Intrinsic::assume || isa<DbgInfoIntrinsic>(II))
return nullptr;
bool Def, Use;

54
llvm/test/Analysis/MemorySSA/debugvalue2.ll Normal file
View File

@ -0,0 +1,54 @@
; RUN: opt -disable-basicaa -print-memoryssa -disable-output %s 2>&1 | FileCheck %s
; Note that the test crashes the MemorySSA verification when doing loop-rotate,
; if debuginfo is modelled in MemorySSA, due to the fact that MemorySSA is not
; updated when adding/removing debuginfo intrinsics.
target triple = "x86_64-unknown-linux-gnu"
; CHECK-LABEL: @overflow_iter_var
; CHECK-NOT: MemoryDef
define void @overflow_iter_var() !dbg !11 {
entry:
call void @llvm.dbg.value(metadata i16 0, metadata !16, metadata !DIExpression()), !dbg !18
br label %for.cond
for.cond: ; preds = %for.body, %entry
call void @llvm.dbg.value(metadata i16 0, metadata !16, metadata !DIExpression()), !dbg !18
call void @llvm.dbg.value(metadata i16 undef, metadata !20, metadata !DIExpression()), !dbg !21
br i1 undef, label %for.end, label %for.body
for.body: ; preds = %for.cond
%0 = load i16, i16* undef, align 1
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
; Function Attrs: nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
attributes #1 = { nounwind readnone speculatable willreturn }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!10}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, nameTableKind: None)
!1 = !DIFile(filename: "2_loops.c", directory: "/")
!2 = !{}
!3 = !{}
!6 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, size: 4096, elements: !8)
!7 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
!8 = !{!9}
!9 = !DISubrange(count: 256)
!10 = !{i32 2, !"Debug Info Version", i32 3}
!11 = distinct !DISubprogram(name: "overflow_iter_var", scope: !1, file: !1, line: 20, type: !12, scopeLine: 21, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
!12 = !DISubroutineType(types: !13)
!13 = !{null, !14, !14}
!14 = !DIBasicType(name: "unsigned int", size: 16, encoding: DW_ATE_unsigned)
!16 = !DILocalVariable(name: "i", scope: !17, file: !1, line: 23, type: !14)
!17 = distinct !DILexicalBlock(scope: !11, file: !1, line: 23, column: 3)
!18 = !DILocation(line: 0, scope: !17)
!20 = !DILocalVariable(name: "stop1", arg: 1, scope: !11, file: !1, line: 20, type: !14)
!21 = !DILocation(line: 0, scope: !11)