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[DCE] Don't remove non-willreturn calls

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In both ADCE and BDCE (via DemandedBits) we should not remove
instructions that are not guaranteed to return. This issue was
pointed out by fhahn in the recent llvm-dev thread.

Differential Revision: https://reviews.llvm.org/D96993
This commit is contained in:
Nikita Popov 2021-02-18 22:29:19 +01:00
parent c1001d823d
commit 93b123f786
10 changed files with 15 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
lib/Analysis/DemandedBits.cpp
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@ -80,7 +80,7 @@ void DemandedBitsWrapperPass::print(raw_ostream &OS, const Module *M) const {
static bool isAlwaysLive(Instruction *I) {
return I->isTerminator() || isa<DbgInfoIntrinsic>(I) || I->isEHPad() ||
I->mayHaveSideEffects();
I->mayHaveSideEffects() || !I->willReturn();
}
void DemandedBits::determineLiveOperandBits(

2
lib/Transforms/Scalar/ADCE.cpp
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@ -325,7 +325,7 @@ void AggressiveDeadCodeElimination::initialize() {
bool AggressiveDeadCodeElimination::isAlwaysLive(Instruction &I) {
// TODO -- use llvm::isInstructionTriviallyDead
if (I.isEHPad() || I.mayHaveSideEffects()) {
if (I.isEHPad() || I.mayHaveSideEffects() || !I.willReturn()) {
// Skip any value profile instrumentation calls if they are
// instrumenting constants.
if (isInstrumentsConstant(I))

4
test/Feature/OperandBundles/adce.ll
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@ -5,8 +5,8 @@
; bundles since the presence of unknown operand bundles implies
; arbitrary memory effects.
declare void @readonly_function() readonly nounwind
declare void @readnone_function() readnone nounwind
declare void @readonly_function() readonly nounwind willreturn
declare void @readnone_function() readnone nounwind willreturn
define void @test0() {
; CHECK-LABEL: @test0(

4
test/LTO/X86/parallel.ll
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@ -11,7 +11,7 @@ target triple = "x86_64-unknown-linux-gnu"
; CHECK0-NOT: bar
; CHECK0: T foo
; CHECK0-NOT: bar
define void @foo() {
define void @foo() mustprogress {
call void @bar()
ret void
}
@ -19,7 +19,7 @@ define void @foo() {
; CHECK1-NOT: foo
; CHECK1: T bar
; CHECK1-NOT: foo
define void @bar() {
define void @bar() mustprogress {
call void @foo()
ret void
}

2
test/Transforms/ADCE/dce_pure_call.ll
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@ -1,6 +1,6 @@
; RUN: opt -adce -S < %s | not grep call
declare i32 @strlen(i8*) readonly nounwind
declare i32 @strlen(i8*) readonly nounwind willreturn
define void @test() {
call i32 @strlen( i8* null ) ; <i32>:1 [#uses=0]

3
test/Transforms/ADCE/willreturn.ll
View File

@ -4,9 +4,10 @@
declare void @may_not_return(i32) nounwind readnone
declare void @will_return(i32) nounwind readnone willreturn
; FIXME: This is a miscompile.
define void @test(i32 %a) {
; CHECK-LABEL: @test(
; CHECK-NEXT: [[B:%.*]] = add i32 [[A:%.*]], 1
; CHECK-NEXT: call void @may_not_return(i32 [[B]])
; CHECK-NEXT: ret void
;
%b = add i32 %a, 1

2
test/Transforms/BDCE/dce-pure.ll
View File

@ -1,7 +1,7 @@
; RUN: opt -bdce -S < %s | FileCheck %s
; RUN: opt -passes=bdce -S < %s | FileCheck %s
declare i32 @strlen(i8*) readonly nounwind
declare i32 @strlen(i8*) readonly nounwind willreturn
define void @test1() {
call i32 @strlen( i8* null )

2
test/Transforms/BDCE/dead-void-ro.ll
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@ -14,5 +14,5 @@ define void @PR34211(i16* %p) {
declare void @no_side_effects_so_dead(i16) #0
attributes #0 = { nounwind readnone }
attributes #0 = { nounwind readnone willreturn }

3
test/Transforms/BDCE/willreturn.ll
View File

@ -4,9 +4,10 @@
declare void @may_not_return(i32) nounwind readnone
declare void @will_return(i32) nounwind readnone willreturn
; FIXME: This is a miscompile.
define void @test(i32 %a) {
; CHECK-LABEL: @test(
; CHECK-NEXT: [[B:%.*]] = add i32 [[A:%.*]], 1
; CHECK-NEXT: call void @may_not_return(i32 [[B]])
; CHECK-NEXT: ret void
;
%b = add i32 %a, 1

4
test/tools/gold/X86/parallel.ll
View File

@ -14,7 +14,7 @@ target triple = "x86_64-unknown-linux-gnu"
; CHECK0-NOT: bar
; CHECK0: T foo
; CHECK0-NOT: bar
define void @foo() {
define void @foo() mustprogress {
call void @bar()
ret void
}
@ -24,7 +24,7 @@ define void @foo() {
; CHECK1-NOT: foo
; CHECK1: T bar
; CHECK1-NOT: foo
define void @bar() {
define void @bar() mustprogress {
call void @foo()
ret void
}