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[NewGVN] Don't derive incorrect implications.

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In the testcase attached,  we believe %tmp1 implies %tmp4.
where:
  br i1 %tmp1, label %bb2, label %bb7
  br i1 %tmp4, label %bb5, label %bb7

because Wwhile looking at PredicateInfo stuffs we end up calling
isImpliedTrueByMatchingCmp() with the arguments backwards.

Differential Revision:  https://reviews.llvm.org/D32718

llvm-svn: 301849
This commit is contained in:
Davide Italiano 2017-05-01 22:26:28 +00:00
parent 0b683165b5
commit 41fbe9a72a
2 changed files with 28 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
lib/Transforms/Scalar/NewGVN.cpp
View File

@ -1628,15 +1628,15 @@ const Expression *NewGVN::performSymbolicCmpEvaluation(Instruction *I) {
if (PBranch->TrueEdge) {
// If we know the previous predicate is true and we are in the true
// edge then we may be implied true or false.
if (CmpInst::isImpliedTrueByMatchingCmp(OurPredicate,
BranchPredicate)) {
if (CmpInst::isImpliedTrueByMatchingCmp(BranchPredicate,
OurPredicate)) {
addPredicateUsers(PI, I);
return createConstantExpression(
ConstantInt::getTrue(CI->getType()));
}
if (CmpInst::isImpliedFalseByMatchingCmp(OurPredicate,
BranchPredicate)) {
if (CmpInst::isImpliedFalseByMatchingCmp(BranchPredicate,
OurPredicate)) {
addPredicateUsers(PI, I);
return createConstantExpression(
ConstantInt::getFalse(CI->getType()));

24
test/Transforms/NewGVN/pr32852.ll Normal file
View File

@ -0,0 +1,24 @@
; Make sure GVN doesn't incorrectly think the branch terminating
; bb2 has a constant condition.
; RUN: opt -S -newgvn %s | FileCheck %s
@a = common global i32 0
@patatino = private unnamed_addr constant [3 x i8] c"0\0A\00"
define void @tinkywinky() {
bb:
%tmp = load i32, i32* @a
%tmp1 = icmp sge i32 %tmp, 0
br i1 %tmp1, label %bb2, label %bb7
bb2:
%tmp4 = icmp sgt i32 %tmp, 0
; CHECK: br i1 %tmp4, label %bb5, label %bb7
br i1 %tmp4, label %bb5, label %bb7
bb5:
%tmp6 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @patatino, i32 0, i32 0))
br label %bb7
bb7:
ret void
}
declare i32 @printf(i8*, ...)