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Don't merge global constants with non-dbg metadata.

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!type metadata can not be dropped. An alternative to this is adding
!type metadata from the replaced globals to the replacement, but that
may weaken type tests and make them slower at the same time.

The merged global gets !dbg metadata from replaced globals, and can
end up with multiple debug locations.

llvm-svn: 297327
This commit is contained in:
Evgeniy Stepanov 2017-03-09 00:03:37 +00:00
parent 086cf9de9d
commit 4759b38338
3 changed files with 96 additions and 0 deletions
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26
lib/Transforms/IPO/ConstantMerge.cpp
View File

@ -60,6 +60,23 @@ static bool IsBetterCanonical(const GlobalVariable &A,
return A.hasGlobalUnnamedAddr();
}
static bool hasMetadataOtherThanDebugLoc(const GlobalVariable *GV) {
SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
GV->getAllMetadata(MDs);
for (const auto &V : MDs)
if (V.first != LLVMContext::MD_dbg)
return true;
return false;
}
static void copyDebugLocMetadata(const GlobalVariable *From,
GlobalVariable *To) {
SmallVector<DIGlobalVariableExpression *, 1> MDs;
From->getDebugInfo(MDs);
for (auto MD : MDs)
To->addDebugInfo(MD);
}
static unsigned getAlignment(GlobalVariable *GV) {
unsigned Align = GV->getAlignment();
if (Align)
@ -113,6 +130,10 @@ static bool mergeConstants(Module &M) {
if (GV->isWeakForLinker())
continue;
// Don't touch globals with metadata other then !dbg.
if (hasMetadataOtherThanDebugLoc(GV))
continue;
Constant *Init = GV->getInitializer();
// Check to see if the initializer is already known.
@ -155,6 +176,9 @@ static bool mergeConstants(Module &M) {
if (!Slot->hasGlobalUnnamedAddr() && !GV->hasGlobalUnnamedAddr())
continue;
if (hasMetadataOtherThanDebugLoc(GV))
continue;
if (!GV->hasGlobalUnnamedAddr())
Slot->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
@ -178,6 +202,8 @@ static bool mergeConstants(Module &M) {
getAlignment(Replacements[i].second)));
}
copyDebugLocMetadata(Replacements[i].first, Replacements[i].second);
// Eliminate any uses of the dead global.
Replacements[i].first->replaceAllUsesWith(Replacements[i].second);

38
test/Transforms/ConstantMerge/dont-merge.ll
View File

@ -42,3 +42,41 @@ define void @test3() {
call void asm sideeffect "T3A, T3B",""() ; invisible use of T3A and T3B
ret void
}
; Don't merge constants with !type annotations.
@T4A1 = internal constant i32 2, !type !0
@T4A2 = internal unnamed_addr constant i32 2, !type !1
@T4B1 = internal constant i32 3, !type !0
@T4B2 = internal unnamed_addr constant i32 3, !type !0
@T4C1 = internal constant i32 4, !type !0
@T4C2 = unnamed_addr constant i32 4
@T4D1 = unnamed_addr constant i32 5, !type !0
@T4D2 = internal constant i32 5
!0 = !{i64 0, !"typeinfo name for A"}
!1 = !{i64 0, !"typeinfo name for B"}
; CHECK: @T4A1
; CHECK: @T4A2
; CHECK: @T4B1
; CHECK: @T4B2
; CHECK: @T4C1
; CHECK: @T4C2
; CHECK: @T4D1
; CHECK: @T4D2
define void @test4(i32** %P1, i32** %P2, i32** %P3, i32** %P4, i32** %P5, i32** %P6, i32** %P7, i32** %P8) {
store i32* @T4A1, i32** %P1
store i32* @T4A2, i32** %P2
store i32* @T4B1, i32** %P3
store i32* @T4B2, i32** %P4
store i32* @T4C1, i32** %P5
store i32* @T4C2, i32** %P6
store i32* @T4D1, i32** %P7
store i32* @T4D2, i32** %P8
ret void
}

32
test/Transforms/ConstantMerge/merge-dbg.ll Normal file
View File

@ -0,0 +1,32 @@
; RUN: opt < %s -constmerge -S | FileCheck %s
; CHECK: = constant i32 1, !dbg [[A:![0-9]+]], !dbg [[B:![0-9]+]]
@a = internal constant i32 1, !dbg !0
@b = unnamed_addr constant i32 1, !dbg !9
define void @test1(i32** %P1, i32** %P2) {
store i32* @a, i32** %P1
store i32* @b, i32** %P2
ret void
}
!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!7, !8}
; CHECK: [[A]] = !DIGlobalVariableExpression(var: [[VA:![0-9]+]])
; CHECK: [[VA]] = distinct !DIGlobalVariable(name: "y"
; CHECK: [[B]] = !DIGlobalVariableExpression(var: [[VB:![0-9]+]])
; CHECK: [[VB]] = distinct !DIGlobalVariable(name: "x"
!0 = !DIGlobalVariableExpression(var: !1)
!1 = distinct !DIGlobalVariable(name: "x", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang version 5.0.0 (trunk 297227) (llvm/trunk 297234)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
!3 = !DIFile(filename: "1.cc", directory: "/build")
!4 = !{}
!5 = !{!0}
!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!7 = !{i32 2, !"Dwarf Version", i32 4}
!8 = !{i32 2, !"Debug Info Version", i32 3}
!9 = !DIGlobalVariableExpression(var: !10)
!10 = distinct !DIGlobalVariable(name: "y", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)