This adds more poison folding optimizations to InstSimplify.

Since all binary operators propagate poison, these are fine.

Also, the precondition of `select cond, undef, x` -> `x` is relaxed to allow the case when `x` is undef.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D104661

Prep work before some cleanup in narrowMaskedBinOp

The reversion apparently deleted the test/Transforms directory.

Will be re-reverting again.

llvm-svn: 358552

As it's causing some bot failures (and per request from kbarton).

This reverts commit r358543/ab70da07.

llvm-svn: 358546

This, in instcombine, allows conversions to i8/i16/i32 (very
common cases) even if the resulting type is not legal according
to the data layout. This can often open up extra combine
opportunities.

Differential Revision: https://reviews.llvm.org/D42424

llvm-svn: 324174

Looks like it's causing timeouts out on at least ppc64le
buildbots.

llvm-svn: 323959

This, in instcombine, allows conversions to i8/i16/i32 (very
common cases) even if the resulting type is not legal according
to the data layout. This can often open up extra combine
opportunities.

Differential Revision: https://reviews.llvm.org/D42424

llvm-svn: 323951

This is guarded by shouldChangeType(), so the tests show that
we don't do the fold if the narrower type is not legal. Note
that there is a proposal (D42424) that would change the results
for the specific cases shown in these tests. That difference is
also discussed in PR35792:
https://bugs.llvm.org/show_bug.cgi?id=35792

Alive proofs for the cases handled here as well as the bitwise 
logic binops that we should already do better on:
https://rise4fun.com/Alive/c97
https://rise4fun.com/Alive/Lc5E
https://rise4fun.com/Alive/kdf

llvm-svn: 323437

llvm-svn: 323436