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From: "zhaoweiliew at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/95424] Failure to optimize division with
 numerator of 1
Date: Fri, 31 Dec 2021 01:16:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95424

Zhao Wei Liew <zhaoweiliew at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #52091|0                           |1
        is obsolete|                            |

--- Comment #2 from Zhao Wei Liew <zhaoweiliew at gmail dot com> ---
Created attachment 52097
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D52097&action=3Dedit
Optimization for both unsigned and signed integer X

I've attached a new patch which does the optimization for both the unsigned=
 and
the signed case.

With this patch, x86-64 gcc -std=3Dc++20 -O3 produces the following assembl=
y:

f(int):
        lea eax, [rdi + 1]
        cmp eax, 2
        mov eax, 0
        cmovbe eax, edi
        ret
f(unsigned int):
        xor eax, eax
        cmp edi, 1
        sete al
        ret

which is virtually identical to the following assembly produced by clang++
-std=3Dc++20 -O3:

f(int):
        lea ecx, [rdi + 1]
        xor eax, eax
        cmp ecx, 3
        cmovb eax, edi
        ret
f(unsigned int):
        xor eax, eax
        cmp edi, 1
        sete al
        ret=