[PATCH] D44365: [X86] Improve codegen of bitcasts of BUILD_VECTOR to MMX register.

Craig Topper via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Sun Mar 11 01:06:17 PST 2018


craig.topper created this revision.
craig.topper added reviewers: spatel, RKSimon.

The 64 bit BUILD_VECTOR is normally going to be promoted to 128 bits by widening each element. This changes the size of each element and requires a shuffle to compress it back down to 64-bits. We also do the copy from XMM to MMX through memory.

This patch pads the vector with undef elements and emits and explicit XMM->MMX copy operation.


Repository:
  rL LLVM

https://reviews.llvm.org/D44365

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/mmx-build-vector.ll
  test/CodeGen/X86/pr29222.ll
  test/CodeGen/X86/vec_insert-mmx.ll

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