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[SimplifyCFG] Don't split musttail call from ret

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Summary:
When inserting an `unreachable` after a noreturn call, we must ensure
that it's not a musttail call to avoid breaking the IR invariants for
musttail calls.

Reviewers: fedor.sergeev, majnemer

Reviewed By: majnemer

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60080

llvm-svn: 357485
This commit is contained in:
Joseph Tremoulet 2019-04-02 15:48:58 +00:00
parent 6a27c48be2
commit fb4d9f7287
2 changed files with 21 additions and 3 deletions
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2
llvm/lib/Transforms/Utils/Local.cpp
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@ -2054,7 +2054,7 @@ static bool markAliveBlocks(Function &F,
Changed = true;
break;
}
if (CI->doesNotReturn()) {
if (CI->doesNotReturn() && !CI->isMustTailCall()) {
// If we found a call to a no-return function, insert an unreachable
// instruction after it. Make sure there isn't *already* one there
// though.

22
llvm/test/Transforms/SimplifyCFG/noreturn-call.ll
View File

@ -1,11 +1,29 @@
; RUN: opt < %s -simplifycfg -S | grep unreachable
; RUN: opt < %s -simplifycfg -S | FileCheck %s
; PR1796
declare void @Finisher(i32) noreturn
define void @YYY(i32) {
; Make sure we optimize a sequence of two calls (second unreachable);
define void @double_call(i32) {
; CHECK-LABEL: @double_call(
; CHECK-NEXT: tail call void @Finisher(i32 %0) #0
; CHECK-NEXT: unreachable
;
tail call void @Finisher(i32 %0) noreturn
tail call void @Finisher(i32 %0) noreturn
ret void
}
; Make sure we DON'T try to optimize a musttail call (the IR invariant
; is that it must be followed by [optional bitcast then] ret).
define void @must_tail(i32) {
; CHECK-LABEL: @must_tail(
; CHECK-NEXT: musttail call void @Finisher(i32 %0) #0
; CHECK-NEXT: ret void
;
musttail call void @Finisher(i32 %0) #0
ret void
}
; CHECK: attributes #0 = { noreturn }
attributes #0 = { noreturn }