[llvm-commits] [llvm] r78714 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/exact-sdiv.ll

[Dan Gohman]

On Aug 11, 2009, at 3:16 PM, Eli Friedman wrote:


> On Tue, Aug 11, 2009 at 1:47 PM, Dan Gohman<gohman at apple.com> wrote:
>
>> Author: djg
>>
>> Date: Tue Aug 11 15:47:47 2009
>>
>> New Revision: 78714
>>
>>
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=78714&view=rev
>>
>> Log:
>>
>> Optimize exact sdiv by a constant power of 2 to ashr.
>>
>
> Do you think we want to optimize exact sdiv by any constant integer in
> instcombine, or should we put that off to CodeGen?  For example,
> should instcombine optimize "exact sdiv i32 %x, 3" to "mul i32 %x,
> 2863311531"?

Instcombine sounds reasonable for this kind of thing, provided that it
happens after any other instcombine rules that know about exact sdiv.

Dan