JIT: Tune CSE/Constant propagation to fix this SIMD example #70657
Description
Found during review of #70654
Vector128<byte> Test(Vector128<byte> a, Vector128<byte> b)
=> Vector128.GreaterThan(a, b);Current codegen:
G_M23213_IG01:
vzeroupper
G_M23213_IG02:
vmovupd xmm0, xmmword ptr [r8]
vpsubb xmm0, xmm0, xmmword ptr [reloc @RWD00]
vmovupd xmm1, xmmword ptr [r9]
vpsubb xmm1, xmm1, xmmword ptr [reloc @RWD00]
vpcmpgtb xmm0, xmm0, xmm1
vmovupd xmmword ptr [rdx], xmm0
mov rax, rdx
G_M23213_IG03:
ret
RWD00 dq 8080808080808080h, 8080808080808080h
; Total bytes of code: 41Here, before vpcmpgtb we subtract a constant vector from both xmm0 and xmm1 - CSE should be able to handle them and give constant propagation a hint that it should not propagate them back.
category:cq
theme:assertion-prop
skill-level:intermediate
cost:small
impact:medium