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[ValueTracking] Fix crash in isGuaranteedNotToBeUndefOrPoison when V is in an unreachable block

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Summary:
This fixes PR45885 by fixing isGuaranteedNotToBeUndefOrPoison so it does not look into dominating
branch conditions of V when V is an instruction in an unreachable block.

Reviewers: spatel, nikic, lebedev.ri

Reviewed By: nikic

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79790
This commit is contained in:
Juneyoung Lee 2020-05-13 00:37:38 +09:00
parent 0796b170fb
commit d3eb51f062
2 changed files with 30 additions and 1 deletions
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7
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -4821,12 +4821,17 @@ bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V,
if (!CtxI || !CtxI->getParent() || !DT)
return false;
auto *DNode = DT->getNode(CtxI->getParent());
if (!DNode)
// Unreachable block
return false;
// If V is used as a branch condition before reaching CtxI, V cannot be
// undef or poison.
// br V, BB1, BB2
// BB1:
// CtxI ; V cannot be undef or poison here
auto Dominator = DT->getNode(CtxI->getParent())->getIDom();
auto *Dominator = DNode->getIDom();
while (Dominator) {
auto *TI = Dominator->getBlock()->getTerminator();

24
llvm/test/Transforms/DivRemPairs/PowerPC/pr45885.ll Normal file
View File

@ -0,0 +1,24 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -div-rem-pairs -S -mtriple=powerpc64-unknown-unknown | FileCheck %s
define void @g() {
; CHECK-LABEL: @g(
; CHECK-NEXT: if.end:
; CHECK-NEXT: ret void
; CHECK: for.cond:
; CHECK-NEXT: [[TMP0:%.*]] = mul i16 [[DIV_I:%.*]], [[REM_FROZEN:%.*]]
; CHECK-NEXT: [[REM_DECOMPOSED:%.*]] = sub i16 1, [[TMP0]]
; CHECK-NEXT: [[REM_FROZEN]] = freeze i16 [[REM_DECOMPOSED]]
; CHECK-NEXT: [[DIV_I]] = sdiv i16 1, [[REM_FROZEN]]
; CHECK-NEXT: br label [[FOR_COND:%.*]]
;
if.end:
ret void
for.cond: ; preds = %for.cond
%rem = srem i16 1, %rem
%div.i = sdiv i16 1, %rem
br label %for.cond
}