[llvm-bugs] [Bug 34911] New: Redundant comparisons are not eliminated

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34911

            Bug ID: 34911
           Summary: Redundant comparisons are not eliminated
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: jmuizelaar at mozilla.com
                CC: llvm-bugs at lists.llvm.org

#include <stdlib.h>
int f(int x) {
        if (x < 4)
                exit(1);
        if (x < 8)
                exit(1);
        if (x < 12)
                exit(1);
        if (x < 16)
                exit(1);
        return x + 5;
}

compiles to:

f(int):                                  # @f(int)
        pushq   %rax
        cmpl    $3, %edi
        jle     .LBB0_5
        cmpl    $7, %edi
        jle     .LBB0_5
        cmpl    $11, %edi
        jle     .LBB0_5
        cmpl    $15, %edi
        jle     .LBB0_5
        addl    $5, %edi
        movl    %edi, %eax
        popq    %rcx
        retq
.LBB0_5:
        movl    $1, %edi
        callq   exit

compared to gcc's

f(int):
        cmpl    $15, %edi
        jle     .L7
        leal    5(%rdi), %eax
        ret
.L7:
        subq    $8, %rsp
        movl    $1, %edi
        call    exit

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