This is a fix for:
https://bugs.llvm.org/show_bug.cgi?id=43730
...and as shown there, we have existing test cases that show potential miscompiles.
We could just bail out for vector constants that contain any undef elements, or we can do as shown here:
allow the transform, but replace the undefs with a safe value.
For most of the tests shown, this results in a full splat constant (no undefs) which is probably a win
for further IR analysis because we conservatively don't match undefs in most cases. Codegen can probably
recover these kinds of undef lanes via demanded elements analysis if that's profitable.
Differential Revision: https://reviews.llvm.org/D69519
The `icmp sgt`/`icmp sle` variants are, too, miscompiles:
https://rise4fun.com/Alive/JFNPhttps://rise4fun.com/Alive/jHvL
A precondition 'x != 0' was forgotten by me.
While ensuring test coverage for `-1`, also add test coverage
for `0` mask. Mask `0` is allowed for all the folds,
mask `-1` is allowed for all the folds with unsigned `icmp` pred.
Constant mask `0` is missed though.
https://bugs.llvm.org/show_bug.cgi?id=42198
llvm-svn: 362910
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Summary:
https://bugs.llvm.org/show_bug.cgi?id=38123
This pattern will be produced by Implicit Integer Truncation sanitizer,
https://reviews.llvm.org/D48958https://bugs.llvm.org/show_bug.cgi?id=21530
in unsigned case, therefore it is probably a good idea to improve it.
https://rise4fun.com/Alive/Rny
^ there are more opportunities for folds, i will follow up with them afterwards.
Caveat: this somehow exposes a missing opportunities
in `test/Transforms/InstCombine/icmp-logical.ll`
It seems, the problem is in `foldLogOpOfMaskedICmps()` in `InstCombineAndOrXor.cpp`.
But i'm not quite sure what is wrong, because it calls `getMaskedTypeForICmpPair()`,
which calls `decomposeBitTestICmp()` which should already work for these cases...
As @spatel notes in https://reviews.llvm.org/D49179#1158760,
that code is a rather complex mess, so we'll let it slide.
Reviewers: spatel, craig.topper
Reviewed By: spatel
Subscribers: yamauchi, majnemer, t.p.northover, llvm-commits
Differential Revision: https://reviews.llvm.org/D49179
llvm-svn: 336834
Sanjay Patel