[llvm-commits] [llvm] r62789 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp lib/CodeGen/SelectionDAG/SelectionDAG.cpp test/CodeGen/X86/negate-add-zero.ll

[Chris Lattner]

On Jan 22, 2009, at 1:58 PM, Dan Gohman wrote:

> Author: djg
> Date: Thu Jan 22 15:58:43 2009
> New Revision: 62789
>
> URL: http://llvm.org/viewvc/llvm-project?rev=62789&view=rev
> Log:
> Don't create ISD::FNEG nodes after legalize if they aren't legal.
>
> Simplify x+0 to x in unsafe-fp-math mode. This avoids a bunch of
> redundant work in many cases, because in unsafe-fp-math mode,
> ISD::FADD with a constant is considered free to negate, so the
> DAGCombiner often negates x+0 to -0-x thinking it's free, when
> in reality the end result is -x, which is more expensive than x.
>
> Also, combine x*0 to 0.
>
> This fixes PR3374.

awesome, thanks Dan!  Can you please use the 'more reduced' testcase  
in the PR, just to reduce the test size?

Thanks,

-Chris