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GlobalDCE: Teach isEmptyFunction() to ignore debug intrinsics.

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This fixes PR39669.
https://bugs.llvm.org/show_bug.cgi?id=39669

llvm-svn: 347065
This commit is contained in:
Adrian Prantl 2018-11-16 17:47:21 +00:00
parent 6b91a7a285
commit 707bb8fc2f
2 changed files with 34 additions and 6 deletions
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15
lib/Transforms/IPO/GlobalDCE.cpp
View File

@ -19,6 +19,7 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/IPO.h"
@ -75,13 +76,17 @@ ModulePass *llvm::createGlobalDCEPass() {
return new GlobalDCELegacyPass();
}
/// Returns true if F contains only a single "ret" instruction.
/// Returns true if F is effectively empty.
static bool isEmptyFunction(Function *F) {
BasicBlock &Entry = F->getEntryBlock();
if (Entry.size() != 1 || !isa<ReturnInst>(Entry.front()))
return false;
ReturnInst &RI = cast<ReturnInst>(Entry.front());
return RI.getReturnValue() == nullptr;
for (auto &I : Entry) {
if (isa<DbgInfoIntrinsic>(I))
continue;
if (auto *RI = dyn_cast<ReturnInst>(&I))
return !RI->getReturnValue();
break;
}
return false;
}
/// Compute the set of GlobalValue that depends from V.

25
test/Transforms/GlobalDCE/global_ctors.ll
View File

@ -1,14 +1,37 @@
; RUN: opt -S -globaldce < %s | FileCheck %s
; Test that the presence of debug intrinsics isn't affecting GlobalDCE.
; CHECK: @llvm.global_ctors = appending global [1 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_notremovable }]
; CHECK-NOT: @_GLOBAL__I_a
declare void @_notremovable()
@llvm.global_ctors = appending global [2 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }, { i32, void ()* } { i32 65535, void ()* @_notremovable }]
@llvm.global_ctors = appending global [3 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }, { i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_b }, { i32, void ()* } { i32 65535, void ()* @_notremovable }]
@x = internal unnamed_addr constant i8 undef, align 1
; Function Attrs: nounwind readnone
define internal void @_GLOBAL__I_a() #1 section "__TEXT,__StaticInit,regular,pure_instructions" {
entry:
ret void
}
; Function Attrs: nounwind readnone
define internal void @_GLOBAL__I_b() #1 section "__TEXT,__StaticInit,regular,pure_instructions" {
entry:
tail call void @llvm.dbg.value(metadata i8* @x, metadata !4, metadata !DIExpression(DW_OP_deref, DW_OP_constu, 0, DW_OP_swap, DW_OP_xderef)), !dbg !5
ret void
}
; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.module.flags = !{!0}
!llvm.dbg.cu = !{!1}
!0 = !{i32 2, !"Debug Info Version", i32 3}
!1 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !2, emissionKind: FullDebug)
!2 = !DIFile(filename: "filename", directory: "directory")
!3 = distinct !DISubprogram(name: "h1", unit: !1)
!4 = !DILocalVariable(name: "b", arg: 1, scope: !3)
!5 = !DILocation(scope: !3)