[llvm-bugs] [Bug 41952] New: [x86] shiftAmountMod should be more eager?

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41952

            Bug ID: 41952
           Summary: [x86] shiftAmountMod should be more eager?
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

unsigned test(unsigned val, unsigned a, unsigned b) {
    unsigned shift = (32 - a) - b;
    return val << shift;
}

clang produces 

        mov     eax, 32
        sub     eax, esi
        sub     eax, edx
        shlx    eax, edi, eax

icc produces

        neg       esi      # <- yay
        sub       esi, edx
        mov       ecx, esi
        shl       edi, cl

https://godbolt.org/z/gdGx_u

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