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Add early exit on reassociation of 0 expression.

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Summary:

Before the patch a try to reassociate ((v * 16) * 0) * 1 fall into infinite loop

Reviewers: pankajchawla

Differential Revision: http://reviews.llvm.org/D41467

From: Evgeny Stupachenko <evstupac@gmail.com>
                         <evgeny.v.stupachenko@intel.com>
llvm-svn: 326861
This commit is contained in:
Evgeny Stupachenko 2018-03-07 02:17:08 +00:00
parent 1feeb98c08
commit 700479379c
2 changed files with 22 additions and 0 deletions
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3
lib/Transforms/Scalar/NaryReassociate.cpp
View File

@ -429,6 +429,9 @@ NaryReassociatePass::tryReassociateGEPAtIndex(GetElementPtrInst *GEP,
Instruction *NaryReassociatePass::tryReassociateBinaryOp(BinaryOperator *I) {
Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
// There is no need to reassociate 0.
if (SE->getSCEV(I)->isZero())
return nullptr;
if (auto *NewI = tryReassociateBinaryOp(LHS, RHS, I))
return NewI;
if (auto *NewI = tryReassociateBinaryOp(RHS, LHS, I))

19
test/Transforms/NaryReassociate/pr35710.ll Normal file
View File

@ -0,0 +1,19 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -nary-reassociate -S | FileCheck %s
; The test check that compilation does not fall into infinite loop.
define i8 @foo(i8 %v) local_unnamed_addr #0 {
; CHECK-LABEL: @foo(
; CHECK-NEXT: region.0:
; CHECK-NEXT: [[TMP0:%.*]] = mul nsw i8 16, [[V:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = mul nsw i8 0, [[TMP0]]
; CHECK-NEXT: [[TMP2:%.*]] = mul nsw i8 1, [[TMP1]]
; CHECK-NEXT: ret i8 [[TMP2]]
;
region.0:
%0 = mul nsw i8 16, %v
%1 = mul nsw i8 0, %0
%2 = mul nsw i8 1, %1
ret i8 %2
}