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| author | Roman Lebedev <lebedev.ri@gmail.com> | 2019-12-02 17:34:55 +0300 |
|---|---|---|
| committer | Roman Lebedev <lebedev.ri@gmail.com> | 2019-12-02 18:06:15 +0300 |
| commit | 0f22e783a038b6983f0fe161eef6cf2add3a4156 (patch) | |
| tree | 9209adbad59a7e9cb742283e2dacfb75a884eff8 /llvm/test/Transforms/LoopUnroll | |
| parent | 241cbf201a6f4b7658697e3c76fc6e741d049a01 (diff) | |
| download | bcm5719-llvm-0f22e783a038b6983f0fe161eef6cf2add3a4156.tar.gz bcm5719-llvm-0f22e783a038b6983f0fe161eef6cf2add3a4156.zip | |
[InstCombine] Revert rL341831: relax one-use check in foldICmpAddConstant() (PR44100)
rL341831 moved one-use check higher up, restricting a few folds
that produced a single instruction from two instructions to the case
where the inner instruction would go away.
Original commit message:
> InstCombine: move hasOneUse check to the top of foldICmpAddConstant
>
> There were two combines not covered by the check before now,
> neither of which actually differed from normal in the benefit analysis.
>
> The most recent seems to be because it was just added at the top of the
> function (naturally). The older is from way back in 2008 (r46687)
> when we just didn't put those checks in so routinely, and has been
> diligently maintained since.
From the commit message alone, there doesn't seem to be a
deeper motivation, deeper problem that was trying to solve,
other than 'fixing the wrong one-use check'.
As i have briefly discusses in IRC with Tim, the original motivation
can no longer be recovered, too much time has passed.
However i believe that the original fold was doing the right thing,
we should be performing such a transformation even if the inner `add`
will not go away - that will still unchain the comparison from `add`,
it will no longer need to wait for `add` to compute.
Doing so doesn't seem to break any particular idioms,
as least as far as i can see.
References https://bugs.llvm.org/show_bug.cgi?id=44100
Diffstat (limited to 'llvm/test/Transforms/LoopUnroll')
| -rw-r--r-- | llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll b/llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll index 9f97358668b..e91bd2eff9c 100644 --- a/llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll +++ b/llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll @@ -578,10 +578,10 @@ define void @test8() { ; PROLOG: %lcmp.mod = icmp eq i64 ; PROLOG-NEXT: br i1 %lcmp.mod, label %innerH.prol.loopexit, label %innerH.prol.preheader ; PROLOG: latch.6: -; PROLOG-NEXT: %tmp4.7 = add nuw nsw i64 %tmp3, 8 ; PROLOG-NEXT: br i1 false, label %outerloop.loopexit.loopexit, label %latch.7 -; PROLOG: latch.7 -; PROLOG-NEXT: %tmp6.7 = icmp ult i64 %tmp4.7, 100 +; PROLOG: latch.7: +; PROLOG-NEXT: %tmp4.7 = add nuw nsw i64 %tmp3, 8 +; PROLOG-NEXT: %tmp6.7 = icmp ult i64 %tmp3, 92 ; PROLOG-NEXT: br i1 %tmp6.7, label %innerH, label %exit.unr-lcssa bb: br label %outerloop |
