[llvm-commits] [PATCH] Add a instcombine optimization.

[Benjamin Kramer]

On 08.07.2010, at 09:12, Duncan Sands wrote:

> Hi Benjamin,
> 
>> The attached patch adds a new transformation to instcombine:
>> (X>s -1) ? C1 : C2 -->  ((X>>s 31)&  (C2 - C1)) + C1
> 
> how about (X >s -1) ? C1 : C2 -->  ((X >>s 31) & (C2 xor C1)) xor C1
> instead?  It might interact better with other bit fiddling optimizations.
> Otherwise the patch looks good.

Hmm, but we wont get a lea on x86 with xor. I don't think xor is profitable
unless we extend the optimization to transform non-const C1 and C2 too.