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llvm-mirror/test/Transforms/LoopSimplify/unreachable-loop-pred.ll
Anna Thomas 5f5dc1a4be [BasicBlockUtils] Check for unreachable preds before updating LI in UpdateAnalysisInformation
Summary:
We are incorrectly updating the LI when loop-simplify generates
dedicated exit blocks for a loop. The issue is that there's an implicit
assumption that the Preds passed into UpdateAnalysisInformation are
reachable. However, this is not true and breaks LI by incorrectly
updating the header of a loop.

One such case is when we generate dedicated exits when the exit block is
a landing pad (through SplitLandingPadPredecessors). There maybe other
cases as well, since we do not guarantee that Preds passed in are
reachable basic blocks.

The added test case shows how loop-simplify breaks LI for the outer loop (and DT in turn)
after we try to generate the LoopSimplifyForm.

Reviewers: davide, chandlerc, sanjoy

Reviewed By: davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D41519

llvm-svn: 321653
2018-01-02 16:25:50 +00:00

70 lines
1.8 KiB
LLVM

; RUN: opt -S -loop-simplify -disable-output -verify-loop-info -verify-dom-info < %s
; PR5235
; When loopsimplify inserts a preheader for this loop, it should add the new
; block to the enclosing loop and not get confused by the unreachable
; bogus loop entry.
define void @is_extract_cab() nounwind {
entry:
br label %header
header: ; preds = %if.end206, %cond.end66, %if.end23
br label %while.body115
while.body115: ; preds = %9, %if.end192, %if.end101
br i1 undef, label %header, label %while.body115
foo:
br label %while.body115
}
; When loopsimplify generates dedicated exit block for blocks that are landing
; pads (i.e. innerLoopExit in this test), we should not get confused with the
; unreachable pred (unreachableB) to innerLoopExit.
define align 8 void @baz(i32 %trip) personality i32* ()* @wobble {
entry:
br label %outerHeader
outerHeader:
invoke void @foo()
to label %innerPreheader unwind label %innerLoopExit
innerPreheader:
br label %innerH
innerH:
%tmp50 = invoke i8 * undef()
to label %innerLatch unwind label %innerLoopExit
innerLatch:
%cmp = icmp slt i32 %trip, 42
br i1 %cmp, label %innerH, label %retblock
unreachableB: ; No predecessors!
%tmp62 = invoke i8 * undef()
to label %retblock unwind label %innerLoopExit
; undedicated exit block (preds from inner and outer loop)
; Also has unreachableB as pred.
innerLoopExit:
%tmp65 = landingpad { i8*, i32 }
cleanup
invoke void @foo()
to label %outerHeader unwind label %unwindblock
unwindblock:
%tmp67 = landingpad { i8*, i32 }
cleanup
ret void
retblock:
ret void
}
; Function Attrs: nounwind
declare i32* @wobble()
; Function Attrs: uwtable
declare void @foo()