[LLVMdev] AVX spill alignment

[Cameron McInally]

Ah, thanks. That seems easy enough.

Sorry to be pedantic, but does that snippet also handle cases where the
frame pointer, %rbp, needs to be 32-byte aligned when dynamic allocas are
present?

I've looked at the ABI, but I don't see any guarantees about 32-byte frame
alignment for AVX. That can be trouble when spill slots are based off of the
frame pointer, not the stack pointer. Please correct me if I'm wrong.

I am working off of a 2.9ish branch, so I would like to cherry pick the
changes I need. If it's too much trouble to pinpoint the source, please say
so.

Tx,
Cameron

On Thursday, September 1, 2011, Jakob Stoklund Olesen <stoklund at 2pi.dk>
wrote:
>
> On Aug 25, 2011, at 4:17 PM, Cameron McInally wrote:
>
>> Hey guys,
>>
>> Are spills/reloads of AVX registers using aligned stores/loads?
>
> Yes.
>
>> I can't
>> seem to find the code that aligns the stack slots to 32-bytes. Could
>> someone point me in the right direction?
>
> The register class has 256-bit spill alignment:
>
> def VR256 : RegisterClass<"X86", [v32i8, v16i16, v8i32, v4i64, v8f32,
v4f64],
>                          256, (sequence "YMM%u", 0, 15)> {
>  let SubRegClasses = [(FR32 sub_ss), (FR64 sub_sd), (VR128 sub_xmm)];
> }
>
> /jakob
>
>
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