[PATCH] D142602: [X86] Expand transform (icmp eq/ne (ABS A), C) -> (and/or (icmp eq/ne A, C), (icmp eq/ne A, -C))

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added a comment.

In D142602#4121033 <https://reviews.llvm.org/D142602#4121033>, @RKSimon wrote:

> Also I'm curious how well this could work on pre-SSSE3 codegen - where we don't have PABS instructions at all

Pre `ssse3` abs gets the following codegen:

  0000000000000000 <abs_v2i64>:
     0:	66 0f 6f c8          	movdqa %xmm0,%xmm1
     4:	66 0f 72 e1 1f       	psrad  $0x1f,%xmm1
     9:	66 0f 70 c9 f5       	pshufd $0xf5,%xmm1,%xmm1
     e:	66 0f ef c1          	pxor   %xmm1,%xmm0
    12:	66 0f fb c1          	psubq  %xmm1,%xmm0
    16:	c3                   	ret    
    17:	66 0f 1f 84 00 00 00 	nopw   0x0(%rax,%rax,1)
    1e:	00 00 
  
  0000000000000020 <abs_v4i32>:
    20:	66 0f 6f c8          	movdqa %xmm0,%xmm1
    24:	66 0f 72 e1 1f       	psrad  $0x1f,%xmm1
    29:	66 0f ef c1          	pxor   %xmm1,%xmm0
    2d:	66 0f fa c1          	psubd  %xmm1,%xmm0
    31:	c3                   	ret    
    32:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
    39:	00 00 00 
    3c:	0f 1f 40 00          	nopl   0x0(%rax)
  
  0000000000000040 <abs_v8i16>:
    40:	66 0f ef c9          	pxor   %xmm1,%xmm1
    44:	66 0f f9 c8          	psubw  %xmm0,%xmm1
    48:	66 0f ee c1          	pmaxsw %xmm1,%xmm0
    4c:	c3                   	ret    
    4d:	0f 1f 00             	nopl   (%rax)
  
  0000000000000050 <abs_v16i8>:
    50:	66 0f ef c9          	pxor   %xmm1,%xmm1
    54:	66 0f f8 c8          	psubb  %xmm0,%xmm1
    58:	66 0f da c1          	pminub %xmm1,%xmm0
    5c:	c3                   	ret    

Probably makes sense for i64 but for the rest will make this only if the node already exists.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142602/new/

https://reviews.llvm.org/D142602