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

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

1 files changed, 66 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Util/clone-dicompileunit.ll b/llvm/test/Transforms/Util/clone-dicompileunit.ll
new file mode 100644
index 00000000000..3f7b5981752
--- /dev/null
+++ b/llvm/test/Transforms/Util/clone-dicompileunit.ll
@@ -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 "}