[llvm-commits] [llvm] r42554 - /llvm/trunk/lib/Target/X86/README.txt

[Bill Wendling]

Sure. I can try to whittle down the testcase that I'm working on.

-bw

On Oct 2, 2007, at 8:35 PM, Chris Lattner wrote:

> Hi Bill,
>
> This is not enough context to reproduce this issue.  Can you please
> include more in the .ll file?  Specifically, the movswl wouldn't
> exist if "tmp654" weren't live out I hope.  It would be best if
> the .ll fragments were actually compilable.
>
> -Chris
>
> On Oct 2, 2007, at 2:49 PM, Bill Wendling wrote:
>
>> Author: void
>> Date: Tue Oct  2 16:49:31 2007
>> New Revision: 42554
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=42554&view=rev
>> Log:
>> Another micro-opt.
>>
>> Modified:
>>     llvm/trunk/lib/Target/X86/README.txt
>>
>> Modified: llvm/trunk/lib/Target/X86/README.txt
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/
>> README.txt?rev=42554&r1=42553&r2=42554&view=diff
>>
>> ===================================================================== 
>> =
>> ========
>> --- llvm/trunk/lib/Target/X86/README.txt (original)
>> +++ llvm/trunk/lib/Target/X86/README.txt Tue Oct  2 16:49:31 2007
>> @@ -1306,3 +1306,19 @@
>>          movl      88(%esp), %eax
>> #481.12
>>
>>  //
>> ===------------------------------------------------------------------ 
>> -
>> --===//
>> +
>> +This code:
>> +
>> +	%tmp659 = icmp slt i16 %tmp654, 0		; <i1> [#uses=1]
>> +	br i1 %tmp659, label %cond_true662, label %cond_next715
>> +
>> +produces this:
>> +
>> +	testw	%cx, %cx
>> +	movswl	%cx, %esi
>> +	jns	LBB4_109	# cond_next715
>> +
>> +Shark tells us that using %cx in the testw instruction is sub-
>> optimal. It
>> +suggests using the 32-bit register (which is what ICC uses).
>> +
>> +//
>> ===------------------------------------------------------------------ 
>> -
>> --===//
>>
>>
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