On Tue, Jun 05, 2018 at 12:26:04PM -0500, Peter Bergner wrote:
> >> -%{mcpu=power8: %(asm_cpu_power8)} \
> >> +%{mcpu=power8: %{!mpower9-vector: %(asm_cpu_power8)}} \
> >> %{mcpu=power9: %(asm_cpu_power9)} \
> >> %{mcpu=a2: -ma2} \
> >> %{mcpu=powerpc: -mppc} \
> >> @@ -169,6 +169,7 @@
> >> %{maltivec: -maltivec} \
> >> %{mvsx: -mvsx %{!maltivec: -maltivec} %{!mcpu*: %(asm_cpu_power7)}} \
> >> %{mpower8-vector|mcrypto|mdirect-move|mhtm: %{!mcpu*: %(asm_cpu_power8)}}
> >> \
> >> +%{mpower9-vector: %{!mcpu*|mcpu=power8: %(asm_cpu_power9)}} \
> >> -many"
> >
> > Why do you need the !mpower9-vector in the mcpu=power8 clause? Is how
> > mpower8-vector is handled not correct, or is something fundamentally
> > different there?
>
> It's fundamentally different because of the overlapping lxvx/stxvx mnemonics
> between P8 and P9, which doesn't occur between any other ISA levels.
> Similar to gcc handling of options, gas uses the last -m<CPU> option to
> assemble with, so if one were to pass -mpower9 -mpower8 to the assembler
> (which you would get if you compile with -mpower9-vector -mcpu=power8),
> then we'd assemble for power8 and get the P8's lxvx extended mnemonic.
> So I've done that to "fix" any ordering issues.
Ah, that's the crux. Thanks. Add a comment to the code please?
> Initially, I was thinking that we should determine what -m<CPU> gas option
> to use by looking at the rs6000_isa_flags value to compute given all of the
> gcc -m* and -mcpu=* options, but unfortunately, the gas option is computed
> in the gcc driver and we don't have access to rs6000_isa_flags. I thought
> the fix above was the least of the bad solutions. :-)
It isn't nice, but it looks like it will work.
Okay for trunk. Thanks,
Segher
