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[NewGVN] Fix handling of assumes

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This patch fixes two bugs:

* test1: Previously assume(a >= 5) concluded that a == 5. That's only
         valid for assume(a == 5)...
* test2: If operands were swapped, additional users were added to the
         wrong cmp operand. This resulted in an "unsettled iteration"
         assertion failure.

Patch by Nikita Popov

Differential Revision: https://reviews.llvm.org/D46974

llvm-svn: 333007
This commit is contained in:
Florian Hahn 2018-05-22 17:38:22 +00:00
parent 44192f816f
commit 2b00b41048
2 changed files with 30 additions and 4 deletions
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8
lib/Transforms/Scalar/NewGVN.cpp
View File

@ -1585,11 +1585,11 @@ NewGVN::performSymbolicPredicateInfoEvaluation(Instruction *I) const {
SwappedOps ? Cmp->getSwappedPredicate() : Cmp->getPredicate();
if (isa<PredicateAssume>(PI)) {
// If the comparison is true when the operands are equal, then we know the
// operands are equal, because assumes must always be true.
if (CmpInst::isTrueWhenEqual(Predicate)) {
// If we assume the operands are equal, then they are equal.
if (Predicate == CmpInst::ICMP_EQ) {
addPredicateUsers(PI, I);
addAdditionalUsers(Cmp->getOperand(0), I);
addAdditionalUsers(SwappedOps ? Cmp->getOperand(1) : Cmp->getOperand(0),
I);
return createVariableOrConstant(FirstOp);
}
}

26
test/Transforms/NewGVN/assumes.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: opt < %s -newgvn -S | FileCheck %s
; CHECK-LABEL: @test1
; CHECK: ret i32 %arg
define i32 @test1(i32 %arg) {
%cmp = icmp sge i32 %arg, 5
call void @llvm.assume(i1 %cmp)
ret i32 %arg
}
; CHECK-LABEL: @test2
; CHECK: ret i32 %arg
define i32 @test2(i32 %arg, i1 %b) {
br label %bb
bb:
%a = phi i32 [ 1, %0 ], [ 2, %bb ]
%cmp = icmp eq i32 %arg, %a
call void @llvm.assume(i1 %cmp)
br i1 %b, label %bb, label %end
end:
ret i32 %arg
}
declare void @llvm.assume(i1 %cond)