[all-commits] [llvm/llvm-project] 961195: [InstCombine] Add test cases to show bad canonical...

[topperc via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 96119586c9968f3c1e56513d52956f5738cf4d26
      https://github.com/llvm/llvm-project/commit/96119586c9968f3c1e56513d52956f5738cf4d26
  Author: Craig Topper <craig.topper at intel.com>
  Date:   2019-11-07 (Thu, 07 Nov 2019)

  Changed paths:
    M llvm/test/Transforms/InstCombine/bitcast-vec-canon.ll

  Log Message:
  -----------
  [InstCombine] Add test cases to show bad canonicalization of bitcasts between x86_mmx and <1 x i64>.

As the test cases show, we end up with an insert/extract and a
bitcast to/from i64. x86_mmx is for some purposes conceptually a
vector. We shouldn't be adding scalar conversions around it.

Since _m64 is defined as <1 x i64> and intrinsics use x86_mmx
as their input/output these extra scalar operations prevent
the X86 backend from generating good code especially on 32-bit
targets where i64 gets split.