[llvm-commits] Patch for X86 to use subregs

[Christopher Lamb]

On Jul 28, 2007, at 1:48 AM, Evan Cheng wrote:

> Very cool! I need to read it more carefully.

> But I see you are lowering zext to a single insert_subreg. Is that  
> right? It won't zero out the top part, no?

It's only lowering (zext i32 to i64) to an insert_subreg on x86-64  
where all writes to 32-bit registers implicitly zero-extend into the  
upper 32-bits.

--
Chris

> Sent from my iPhone
>
> On Jul 28, 2007, at 12:17 AM, Christopher Lamb  
> <christopher.lamb at gmail.com> wrote:
>
>> This patch changes the X86 back end to use the new subreg  
>> operations for appropriate truncate and extend operations. This  
>> should allow regression testing of the subreg feature going  
>> forward, as it's now used in a public target.
>>
>> The patch passed DejaGnu and all of SingleSource on my x86  
>> machine, but there are changes for x86-64 as well which I haven't  
>> been able to test. Output assembly for x86-64 appears sane, but  
>> I'd appreciate someone giving the patch a try on their x86-64  
>> system. Other 32-bit x86 testing is also appreciated.
>>
>> Thanks
>> --
>> Christopher Lamb
>>
>> <x86_subregs.patch>
>>
>>
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--
Christopher Lamb



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