[PATCH] D150360: [InstSimplify] Optimize compares with multiple selects as operands

[Tejas Joshi via Phabricator via llvm-commits]

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In case of a comparison with two select instructions having the same
condition, try to simplify the comparison by checking whether all
combinations of branches of the select result in the same value. Returns
the common value if so, otherwise returns null.
For example, if we have:
 %tmp1 = select i1 %cmp, i32 1, i32 %param
 %tmp2 = select i1 %cmp, i32 9, i32 %param
 %cmp2 = icmp slt i32 %tmp2, %tmp1
We can simplify %cmp2 to false, because both branches of both the selects
will result false.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150360

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/icmp-with-selects.ll

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