[PATCH] Improve out-of-SSA coalescing
Richard Biener
rguenther@suse.de
Wed Sep 25 13:29:00 GMT 2013
On Wed, 25 Sep 2013, Richard Biener wrote:
>
> This loosens the restriction of only coalescing SSA names with
> the same base variable by ignoring that restriction for DECL_INGORED_P
> base variables (ok, all of them can and should be anonymous SSA names
> now, but code obviously hasn't catched up 100%).
>
> This improves the code generated for the loop in the testcase to
>
> <fallthru>
> .p2align 4,,10
> .p2align 3
> .L4:
> xorps %xmm1, %xmm1
> cvtsi2ss %eax, %xmm1
> addl $1, %eax
> cmpl %edi, %eax
> addss %xmm1, %xmm0
> jne .L4
>
> from
>
> jmp .L4
> .p2align 4,,10
> .p2align 3
> .L6:
> movaps %xmm0, %xmm1
> .L4:
> xorps %xmm0, %xmm0
> cvtsi2ss %eax, %xmm0
> addl $1, %eax
> cmpl %edi, %eax
> addss %xmm1, %xmm0
> jne .L6
>
> avoiding the copy on the backedge and the loop entry jump. Overall
> this is similar to what Jeff was after with his latest adjustment
> of this code.
>
> Bootstrap and regtest ongoing on x86_64-unknown-linux-gnu.
For some reason it miscompiles GCC itself. Hmm. Cannot spot the
obvious error yet.
Richard.
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