[llvm-commits] [llvm] r77989 - in /llvm/trunk: lib/CodeGen/LowerSubregs.cpp lib/CodeGen/MachineInstr.cpp test/CodeGen/ARM/2009-08-02-RegScavengerAssert-Neon.ll

[Jakob Stoklund Olesen]

On 04/08/2009, at 21.36, Evan Cheng wrote:
>> We will almost certainly need to insert fake instructions that only
>> change flags. I am using IMPLICIT_DEF for that now, but it should
>> probably be replaced by a new ALTER_LIFE or something.
>
> I suggest KILL. It's easy to understand.

ALTER_LIFE is silly, but the instruction can also make registers live:

subreg: CONVERTING: %R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
subreg: replace by: %R2L<def> = IMPLICIT_DEF %R2<kill>

subreg: CONVERTING: %R0<def> = INSERT_SUBREG %R0<undef>, %R0L<kill>, 1
subreg: replace by: %R0<def> = IMPLICIT_DEF %R0L<imp-use,kill>

[...]

>> Am I on the right track?
>
> Very much so! Thanks for working on this.

Woot! Finally.