[PATCH] D17032: [X86] Add a pass to change byte and word instructions to zero-extending versions.

[Kevin B. Smith via llvm-commits]

kbsmith1 created this revision.
kbsmith1 added reviewers: DavidKreitzer, spatel, qcolombet.
kbsmith1 added a subscriber: llvm-commits.

This change adds a pass (which will be currently turned off by default) that can change
byte and word instructions into zero extending instructions.  This is an attempt to improve
performance by eliminating some penalties associated with the byte and word versions
of load instructions only at this time.  My vision, however, is that this should be able to
be extended over time to provide much more optimization of byte and word instructions
into more efficient forms.
This is intended to eventually solve: https://llvm.org/bugs/show_bug.cgi?id=23155
but won't until turned on by default.

http://reviews.llvm.org/D17032

Files:
  lib/Target/X86/CMakeLists.txt
  lib/Target/X86/X86.h
  lib/Target/X86/X86FixupBWInsts.cpp
  lib/Target/X86/X86TargetMachine.cpp
  test/CodeGen/X86/fixup-bw-inst.ll

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