Benjamin Kramer 341c11da3b DAGCombine: fold "(zext x) == C" into "x == (trunc C)" if the trunc is lossless. ...

On x86 this allows to fold a load into the cmp, greatly reducing register pressure.
  movzbl	(%rdi), %eax
  cmpl	$47, %eax
->
  cmpb	$47, (%rdi)

This shaves 8k off gcc.o on i386. I'll leave applying the patch in README.txt to Chris :)

llvm-svn: 130005

2011-04-22 18:47:44 +00:00

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