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[LoopPred] Fix a bug in unconditional latch bailout introduced in r362284 

This is a really silly bug that even a simple test w/an unconditional latch would have caught.  I tried to guard against the case, but put it in the wrong if check.  Oops.

llvm-svn: 362727
This commit is contained in:
Philip Reames 2019-06-06 18:02:36 +00:00
parent bd9e810b23
commit 101915cfda
2 changed files with 28 additions and 2 deletions
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4
llvm/lib/Transforms/Scalar/LoopPredication.cpp
View File

@ -850,7 +850,7 @@ Optional<LoopICmp> LoopPredication::parseLoopLatchICmp() {
}
auto *BI = dyn_cast<BranchInst>(LoopLatch->getTerminator());
if (!BI) {
if (!BI || !BI->isConditional()) {
LLVM_DEBUG(dbgs() << "Failed to match the latch terminator!\n");
return None;
}
@ -860,7 +860,7 @@ Optional<LoopICmp> LoopPredication::parseLoopLatchICmp() {
"One of the latch's destinations must be the header");
auto *ICI = dyn_cast<ICmpInst>(BI->getCondition());
if (!ICI || !BI->isConditional()) {
if (!ICI) {
LLVM_DEBUG(dbgs() << "Failed to match the latch condition!\n");
return None;
}

26
llvm/test/Transforms/LoopPredication/basic.ll
View File

@ -1853,3 +1853,29 @@ exit:
ret i32 0
}
; Negative test, make sure we don't crash on unconditional latches
; TODO: there's no reason we shouldn't be able to predicate the
; condition for an statically infinite loop.
define i32 @unconditional_latch(i32* %a, i32 %length) {
; CHECK-LABEL: @unconditional_latch(
; CHECK-NEXT: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ 400, [[LOOP_PREHEADER:%.*]] ]
; CHECK-NEXT: [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[I]], [[LENGTH:%.*]]
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 [[WITHIN_BOUNDS]], i32 9) [ "deopt"() ]
; CHECK-NEXT: store volatile i32 0, i32* [[A:%.*]]
; CHECK-NEXT: [[I_NEXT]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[LOOP]]
;
loop.preheader:
br label %loop
loop:
%i = phi i32 [ %i.next, %loop ], [ 400, %loop.preheader ]
%within.bounds = icmp ult i32 %i, %length
call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
store volatile i32 0, i32* %a
%i.next = add i32 %i, 1
br label %loop
}