[LLVMbugs] [Bug 4841] [x86] cmov generated even on -mcpu=pentium

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Mar 21 16:55:15 PDT 2010


Craig Smith <craig at ni.com> changed:

           What    |Removed                     |Added
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |

--- Comment #9 from Craig Smith <craig at ni.com> 2010-03-21 18:55:15 CDT ---
I'm reopening this because the current patch, while disabling CMOV and FCMOV
instructions, fails to also
disable the FCOMI/FCOMIP/ FUCOMI/FUCOMIP instructions which were added to the
Pentium Pro at the same time as conditional moves. 

There don't seem to be any models of CPU which support FCOMI and friends but do
not support conditional moves, so it makes sense to tie them to the -cmov
attribute as well.

As it stands, using -cmov is not sufficient to generate code which will run on
pentium and earlier CPUs.

I'm attaching a proposed patch which ties FCOMI, etc. to the -cmov attribute.

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