Sanjay Patel 39e602b6c4 [InstCombine] try to fold binop with phi operands ...

This is an alternate version of D115914 that handles/tests all binary opcodes.

I suspect that we don't see these patterns too often because -simplifycfg
would convert the minimal cases into selects rather than leave them in phi form
(note: instcombine has logic holes for combining the select patterns too though,
so that's another potential patch).

We only create a new binop in a predecessor that unconditionally branches to
the final block.
https://alive2.llvm.org/ce/z/C57M2F
https://alive2.llvm.org/ce/z/WHwAoU (not safe to speculate an sdiv for example)
https://alive2.llvm.org/ce/z/rdVUvW (but it is ok on this path)

Differential Revision: https://reviews.llvm.org/D117110

2022-01-22 15:00:06 -05:00

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