[llvm-commits] VECTOR_SUFFLE in avx - fixed - Please review

[Rotem, Nadav]

Craig,

It looks like some node (scalar_to_vector in our case) is legalized into an UNDEF and the result is replaced using "DAG.ReplaceAllUsesWith".  I don't think that we can do much about it. Let's do what Duncan said.

Nadav

From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Craig Topper
Sent: Wednesday, January 11, 2012 19:58
To: Duncan Sands
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] VECTOR_SUFFLE in avx - fixed - Please review

r147525 added canonicalizing to DAGCombiner that should make shuffles of two undefs turn into an undef. Is that code not working correctly for this case?

On Wed, Jan 11, 2012 at 3:55 AM, Duncan Sands <baldrick at free.fr<mailto:baldrick at free.fr>> wrote:
Hi Elena,

> Fixed a bug in VECTOR_SHUFFLE
> lc: X86ISelLowering.cpp:6480: llvm::SDValue llvm::X86TargetLowering::LowerVECTOR_SHUFFLE(llvm::SDValue, llvm::SelectionDAG&) const: Assertion `V1.getOpcode() != ISD::UNDEF&&  "Op 1 of shuffle should not be undef"' failed.

if V1 is undef but V2IsUndef is false then you can now fall through to the
following code.  How about at restoring the assertion, but putting it after
your test.  While there, maybe introduce V1IsUndef for neatness.

Ciao, Duncan.
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~Craig
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