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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/114514] v16qi >> 7 can be optimized with vpcmpgtb
Date: Thu, 28 Mar 2024 23:14:04 +0000	[thread overview]
Message-ID: <bug-114514-4-yxVpZeic8d@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-114514-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114514

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
For non constant clang produces:
```
signedshiftright:
        movzbl  %dil, %eax
        movd    %eax, %xmm1
        psrlw   %xmm1, %xmm0
        pcmpeqd %xmm2, %xmm2
        psrlw   %xmm1, %xmm2
        movdqa  .LCPI0_0(%rip), %xmm3           # xmm3 =
[32896,32896,32896,32896,32896,32896,32896,32896]
        psrlw   %xmm1, %xmm3
        psrlw   $8, %xmm2
        punpcklbw       %xmm2, %xmm2            # xmm2 =
xmm2[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
        pshuflw $0, %xmm2, %xmm1                # xmm1 = xmm2[0,0,0,0,4,5,6,7]
        pshufd  $0, %xmm1, %xmm1                # xmm1 = xmm1[0,0,0,0]
        pand    %xmm1, %xmm0
        pxor    %xmm3, %xmm0
        psubb   %xmm3, %xmm0
        retq

unsignedshiftrtight:
        movzbl  %dil, %eax
        movd    %eax, %xmm1
        psrlw   %xmm1, %xmm0
        pcmpeqd %xmm2, %xmm2
        psrlw   %xmm1, %xmm2
        psrlw   $8, %xmm2
        punpcklbw       %xmm2, %xmm2            # xmm2 =
xmm2[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
        pshuflw $0, %xmm2, %xmm1                # xmm1 = xmm2[0,0,0,0,4,5,6,7]
        pshufd  $0, %xmm1, %xmm1                # xmm1 = xmm1[0,0,0,0]
        pand    %xmm1, %xmm0
        retq
```

I am not sure which way is faster here though.

  parent reply	other threads:[~2024-03-28 23:14 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-28  9:38 [Bug target/114514] New: " liuhongt at gcc dot gnu.org
2024-03-28 23:09 ` [Bug target/114514] " pinskia at gcc dot gnu.org
2024-03-28 23:14 ` pinskia at gcc dot gnu.org [this message]
2024-03-29  1:03 ` liuhongt at gcc dot gnu.org

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