[Bug target/53507] ia32/amd64: bsf can be used to test null memory, bsf sets zero flag

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53507

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|rtl-optimization            |target
           Keywords|                            |missed-optimization
   Last reconfirmed|                            |2021-11-29
             Status|UNCONFIRMED                 |NEW
             Target|                            |x86_64 i?86
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
LLVM does:
testnull():                           # @testnull()
        .cfi_startproc
# %bb.0:
        cmpl    $0, I
        je      .LBB0_2
# %bb.1:
        retl
.LBB0_2:
        jmp     ifnull()