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[DCE] Salvage debug info from dead insts

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This results in small increases in the size of the .debug_loc section
and the number of unique source variables in a stage2 build of opt.

llvm-svn: 325301
This commit is contained in:
Vedant Kumar 2018-02-15 22:26:18 +00:00
parent 42ad8b2929
commit 02a33aae11
2 changed files with 11 additions and 4 deletions
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3
lib/Transforms/Scalar/DCE.cpp
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@ -50,6 +50,7 @@ namespace {
for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
Instruction *Inst = &*DI++;
if (isInstructionTriviallyDead(Inst, TLI)) {
salvageDebugInfo(*Inst);
Inst->eraseFromParent();
Changed = true;
++DIEEliminated;
@ -76,6 +77,8 @@ static bool DCEInstruction(Instruction *I,
SmallSetVector<Instruction *, 16> &WorkList,
const TargetLibraryInfo *TLI) {
if (isInstructionTriviallyDead(I, TLI)) {
salvageDebugInfo(*I);
// Null out all of the instruction's operands to see if any operand becomes
// dead as we go.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {

12
test/Transforms/DCE/basic.ll
View File

@ -1,11 +1,15 @@
; RUN: opt -dce -S < %s | FileCheck %s
; RUN: opt -passes=dce -S < %s | FileCheck %s
; RUN: opt -debugify -dce -S < %s | FileCheck %s
; RUN: opt -passes='module(debugify),function(dce)' -S < %s | FileCheck %s
; CHECK-LABEL: @test
define void @test() {
; CHECK-NOT: add
%add = add i32 1, 2
; CHECK-NOT: sub
; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 1, metadata [[add:![0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 2, DW_OP_stack_value))
%sub = sub i32 %add, 1
; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 1, metadata [[sub:![0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 2, DW_OP_constu, 1, DW_OP_minus, DW_OP_stack_value))
; CHECK-NEXT: ret void
ret void
}
; CHECK: [[add]] = !DILocalVariable
; CHECK: [[sub]] = !DILocalVariable