On Mon, Jun 04, 2018 at 08:57:24PM -0500, Peter Bergner wrote:
> PR63177 shows a bug in how we determine which gas options we decide to pass
> to the
> assembler. Normally, we pass the -m<CPU> option to the assembler if we used
> the
> -mcpu=<CPU> option. However, if we don't compile with -mcpu=<CPU>, then we
> will
> check some of the -m<vector option> options and pass an appropriate -m<CPU>
> option
> to the assembler. This is all fine and good except for when we compile with
> -mpower9-vector -mcpu=power8. The problem here is that POWER9 added new
> lxvx/stxvx
> instructions which already existed in POWER8 as extended mnemonics of
> lxvd2x/stxvd2x
> which are different instructions and behave differently in LE mode. The
> "bug" is
> that -mpower9-vector enables the generation of the POWER9 lxvx instruction,
> but the
> -mcpu=power8 option causes us to use the -mpower8 assembler option so we get
> the
> wrong instruction. :-(
>
> The fix used here is to catch the special case when we use -mpower9-vector and
> -mcpu=power8 together and then force ourselves to use the -mpower9 gas option.
Ideally -mpowerN-vector will just go away.
> --- gcc/config/rs6000/rs6000.h (revision 260913)
> +++ gcc/config/rs6000/rs6000.h (working copy)
> @@ -120,7 +120,7 @@
> %{mcpu=power6: %(asm_cpu_power6) -maltivec} \
> %{mcpu=power6x: %(asm_cpu_power6) -maltivec} \
> %{mcpu=power7: %(asm_cpu_power7)} \
> -%{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?
Segher
