[llvm-bugs] [Bug 46967] New: Use less constants in clamp codegen

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46967

            Bug ID: 46967
           Summary: Use less constants in clamp codegen
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: david.bolvansky at gmail.com
                CC: llvm-bugs at lists.llvm.org

int fast_min(int x, int y) {
    return (x < y) ? x : y;
}

int fast_max(int x, int y) {
    return (x > y) ? x : y;
}

int fast_clamp(int x, int min, int max) {
    return fast_max(fast_min(x, max), min);
}

int use_fast_clamp(int x) {
    return fast_clamp(x, 128, 255);
}

Clang:
use_fast_clamp:                         # @use_fast_clamp
        cmp     edi, 256
        mov     ecx, 255
        cmovl   ecx, edi
        cmp     ecx, 127
        mov     eax, 128
        cmovg   eax, ecx
        ret

GCC:
use_fast_clamp:
        mov     eax, 255
        mov     edx, 128
        cmp     edi, eax
        cmovle  eax, edi
        cmp     eax, edx
        cmovl   eax, edx
        ret

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