[Bug target/109463] suboptimal sequence for converting 64-bit unsigned int to float

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109463

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
           Keywords|                            |missed-optimization

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
clang/LLVM produces:

        movq    %rdi, %xmm1
        punpckldq       .LCPI1_0(%rip), %xmm1   # xmm1 =
xmm1[0],mem[0],xmm1[1],mem[1]
        subpd   .LCPI1_1(%rip), %xmm1
        movapd  %xmm1, %xmm0
        unpckhpd        %xmm1, %xmm0                    # xmm0 =
xmm0[1],xmm1[1]
        addsd   %xmm1, %xmm0
        retq

LCPI1_0 being:
.LCPI1_1:
        .quad   0x4330000000000000              # double 4503599627370496
        .quad   0x4530000000000000              # double 1.9342813113834067E+25


note clang even produces that even if you say the top bit is not set via:
double f(unsigned long x) { if (x >>63) __builtin_unreachable(); return x; }