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IR: Consider two DISubprograms to be odr-equal if they have the same template parameters.

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In ValueMapper we create new operands for MDNodes and
rely on MDNode::replaceWithUniqued to create a new MDNode
with the specified operands. However this doesn't always
actually happen correctly for DISubprograms because when we
uniquify the new node, we only odr-compare it with existing nodes
(MDNodeSubsetEqualImpl<DISubprogram>::isDeclarationOfODRMember). Although
the TemplateParameters field can refer to a distinct DICompileUnit via
DITemplateTypeParameter::type -> DICompositeType::scope -> DISubprogram::unit,
it is not currently included in the odr comparison. As a result, we can end
up getting our original DISubprogram back, which means we will have a cloned
module referring to the DICompileUnit in the original module, which causes
a verification error.

The fix I implemented was to consider TemplateParameters to be one of the
odr-equal properties. But I'm a little uncomfortable with this. In general it
seems unsound to rely on distinct MDNodes never being reachable from nodes
which we only check odr-equality of. My only long term suggestion would be
to separate odr-uniquing from full uniquing.

Differential Revision: https://reviews.llvm.org/D29240

llvm-svn: 294240
This commit is contained in:
Peter Collingbourne 2017-02-06 21:23:03 +00:00
parent b408a28a3a
commit c382eafa00
2 changed files with 77 additions and 3 deletions
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14
lib/IR/LLVMContextImpl.h
View File

@ -612,17 +612,19 @@ template <> struct MDNodeSubsetEqualImpl<DISubprogram> {
typedef MDNodeKeyImpl<DISubprogram> KeyTy;
static bool isSubsetEqual(const KeyTy &LHS, const DISubprogram *RHS) {
return isDeclarationOfODRMember(LHS.IsDefinition, LHS.Scope,
LHS.LinkageName, RHS);
LHS.LinkageName, LHS.TemplateParams, RHS);
}
static bool isSubsetEqual(const DISubprogram *LHS, const DISubprogram *RHS) {
return isDeclarationOfODRMember(LHS->isDefinition(), LHS->getRawScope(),
LHS->getRawLinkageName(), RHS);
LHS->getRawLinkageName(),
LHS->getRawTemplateParams(), RHS);
}
/// Subprograms compare equal if they declare the same function in an ODR
/// type.
static bool isDeclarationOfODRMember(bool IsDefinition, const Metadata *Scope,
const MDString *LinkageName,
const Metadata *TemplateParams,
const DISubprogram *RHS) {
// Check whether the LHS is eligible.
if (IsDefinition || !Scope || !LinkageName)
@ -633,8 +635,14 @@ template <> struct MDNodeSubsetEqualImpl<DISubprogram> {
return false;
// Compare to the RHS.
// FIXME: We need to compare template parameters here to avoid incorrect
// collisions in mapMetadata when RF_MoveDistinctMDs and a ODR-DISubprogram
// has a non-ODR template parameter (i.e., a DICompositeType that does not
// have an identifier). Eventually we should decouple ODR logic from
// uniquing logic.
return IsDefinition == RHS->isDefinition() && Scope == RHS->getRawScope() &&
LinkageName == RHS->getRawLinkageName();
LinkageName == RHS->getRawLinkageName() &&
TemplateParams == RHS->getRawTemplateParams();
}
};

66
test/Transforms/Util/clone-dicompileunit.ll Normal file
View File

@ -0,0 +1,66 @@
; RUN: opt -run-twice -verify -disable-debug-info-type-map -S -o - %s | FileCheck %s
; Generated using:
; $ cat p.cpp
; void sink(void *);
; class A {
; public:
; template <typename> void m_fn2() { static int a; }
; virtual void m_fn1();
; };
; void foo() {
; class B : public A {
; public:
; B() { m_fn2<B>(); }
; };
; sink(new B);
; }
; $ clang++ -target x86_64-unknown-linux -fvisibility=hidden -O2 -g2 -flto -S p.cpp -o p.ll
; # then manually removed function/gv definitions
; Test that when the module is cloned it does not contain a reference to
; the original DICompileUnit as a result of a collision between the cloned
; DISubprogram for m_fn2<B> (which refers to the non-ODR entity B via
; template parameters) and the original DISubprogram.
; CHECK: DICompileUnit
; CHECK-NOT: DICompileUnit
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux"
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!28, !29}
!llvm.ident = !{!30}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 5.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3)
!1 = !DIFile(filename: "p.cpp", directory: "/usr/local/google/home/pcc/b682773-2-repro/small2")
!2 = !{}
!3 = !{!4}
!4 = !DIGlobalVariableExpression(var: !5)
!5 = distinct !DIGlobalVariable(name: "a", scope: !6, file: !1, line: 5, type: !27, isLocal: true, isDefinition: true)
!6 = distinct !DISubprogram(name: "m_fn2<B>", linkageName: "_ZN1A5m_fn2IZ3foovE1BEEvv", scope: !7, file: !1, line: 5, type: !8, isLocal: true, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !11, declaration: !23, variables: !24)
!7 = !DICompositeType(tag: DW_TAG_class_type, name: "A", file: !1, line: 3, flags: DIFlagFwdDecl, identifier: "_ZTS1A")
!8 = !DISubroutineType(types: !9)
!9 = !{null, !10}
!10 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !7, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
!11 = !{!12}
!12 = !DITemplateTypeParameter(type: !13)
!13 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "B", scope: !14, file: !1, line: 10, size: 64, elements: !17, vtableHolder: !7)
!14 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 9, type: !15, isLocal: false, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
!15 = !DISubroutineType(types: !16)
!16 = !{null}
!17 = !{!18, !19}
!18 = !DIDerivedType(tag: DW_TAG_inheritance, scope: !13, baseType: !7, flags: DIFlagPublic)
!19 = !DISubprogram(name: "B", scope: !13, file: !1, line: 12, type: !20, isLocal: false, isDefinition: false, scopeLine: 12, flags: DIFlagPublic | DIFlagPrototyped, isOptimized: true)
!20 = !DISubroutineType(types: !21)
!21 = !{null, !22}
!22 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
!23 = !DISubprogram(name: "m_fn2<B>", linkageName: "_ZN1A5m_fn2IZ3foovE1BEEvv", scope: !7, file: !1, line: 5, type: !8, isLocal: false, isDefinition: false, scopeLine: 5, flags: DIFlagPublic | DIFlagPrototyped, isOptimized: true, templateParams: !11)
!24 = !{!25}
!25 = !DILocalVariable(name: "this", arg: 1, scope: !6, type: !26, flags: DIFlagArtificial | DIFlagObjectPointer)
!26 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !7, size: 64)
!27 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!28 = !{i32 2, !"Dwarf Version", i32 4}
!29 = !{i32 2, !"Debug Info Version", i32 3}
!30 = !{!"clang version 5.0.0 "}