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[InstCombine] Fix div handling

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When we optimize select basing on fact that div by 0 is undef
we should not traverse the instruction which are not guaranteed to
transfer execution to next instruction. Guard intrinsic is an example.

Reviewers: spatel, craig.topper
Reviewed By: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D47576

llvm-svn: 333864
This commit is contained in:
Serguei Katkov 2018-06-04 02:52:36 +00:00
parent 56aff921dc
commit 8b2aa5885a
2 changed files with 5 additions and 6 deletions
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4
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -581,9 +581,9 @@ bool InstCombiner::simplifyDivRemOfSelectWithZeroOp(BinaryOperator &I) {
Type *CondTy = SelectCond->getType();
while (BBI != BBFront) {
--BBI;
// If we found a call to a function, we can't assume it will return, so
// If we found an instruction that we can't assume will return, so
// information from below it cannot be propagated above it.
if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
if (!isGuaranteedToTransferExecutionToSuccessor(&*BBI))
break;
// Replace uses of the select or its condition with the known values.

7
test/Transforms/InstCombine/sdiv-guard.ll
View File

@ -3,11 +3,11 @@
declare void @llvm.experimental.guard(i1, ...)
; FIXME: If %flag is false then %s == 0 and guard should be triggered.
; Regression test. If %flag is false then %s == 0 and guard should be triggered.
define i32 @a(i1 %flag, i32 %X) nounwind readnone {
; CHECK-LABEL: @a(
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[X:%.*]], 0
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[X:%.*]], 0
; CHECK-NEXT: [[CMP:%.*]] = and i1 [[CMP1]], [[FLAG:%.*]]
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 [[CMP]]) #1 [ "deopt"() ]
; CHECK-NEXT: [[R:%.*]] = sdiv i32 100, [[X]]
; CHECK-NEXT: ret i32 [[R]]
@ -18,4 +18,3 @@ define i32 @a(i1 %flag, i32 %X) nounwind readnone {
%r = sdiv i32 100, %s
ret i32 %r
}