On Fri, 2020-03-27 at 21:31 -0400, Michael Meissner via Gcc-patches
wrote:
Hi,
A few cosmetic nits and comments sprinkled in below. I defer to
Segher for his approvals and comments. thanks,
-Will
> This is a revised version of the patch I posted on March 23rd. The
> changes are
> to update the comments and improve the ChangeLog.
Missing the description of what the patch actually does.
(From Mar 23):
> It makes
> -mpcrel the default on Linux 64-bit systems that use ELF v2, use the medium
> code mode, and if the user did not disable prefixed load/store instructions
> for
> -mcpu=future.
> There were no regressions when I did the bootstrap and make check
> steps. I
> verified that -mcpu=future does turn on -mprecl if you are targeting
> a Linux
-mpcrel
> ELF v2 system and use the medium code model. Can I check this into
> the master
> branch?
>
> 2020-03-27 Michael Meissner <meiss...@linux.ibm.com>
>
> * config/rs6000/linux64.h (PCREL_SUPPORTED_BY_OS): New macro.
> * config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): Do
> not
> set -mprefixed here.
> * config/rs6000/rs6000.c (PCREL_SUPPORTED_BY_OS): New macro.
> (rs6000_option_override_internal): Set the -mprefixed and
> -mpcrel
> options for -mcpu=future if these options can be used.
>
s/can be used/are supported by the platform/ ?
> --- /tmp/JVBhAf_linux64.h 2020-03-27 16:27:05.478619500 -0400
> +++ gcc/config/rs6000/linux64.h 2020-03-27 16:21:56.268876616
> -0400
> @@ -640,3 +640,11 @@ extern int dot_symbols;
> enabling the __float128 keyword. */
> #undef TARGET_FLOAT128_ENABLE_TYPE
> #define TARGET_FLOAT128_ENABLE_TYPE 1
> +
> +/* Enable default support for PC-relative addressing on the 'future'
> system if
> + we can use the PC-relative instructions. Currently this support
> only exits
exists
> + for the ELF v2 object file format using the medium code
> model. */
should that be "s/object file format/ABI/" ?
> +#undef PCREL_SUPPORTED_BY_OS
> +#define PCREL_SUPPORTED_BY_OS (TARGET_FUTURE &&
> TARGET_PREFIXED \
> + && ELFv2_ABI_CHECK
> \
> + && (TARGET_CMODEL == CMODEL_MEDIUM))
> --- /tmp/KyQOUN_rs6000-cpus.def 2020-03-27 16:27:05.488619427
> -0400
> +++ gcc/config/rs6000/rs6000-cpus.def 2020-03-27 16:23:51.780030238
> -0400
> @@ -75,11 +75,11 @@
> | OPTION_MASK_P8_VECTOR \
> | OPTION_MASK_P9_VECTOR)
>
> -/* Support for a future processor's features. Do not enable -mpcrel
> until it
> - is fully functional. */
> +/* Support for a future processor's features. We do not set -mpcrel
> or
> + -mprefixed here. These bits are set in rs6000_option_override if
> the system
> + supports those options. */
I'm still not sure the comment here is actually necessary, there are
many other places where we also do not set -mpcrel or -mprefixed. If
history of the code here requires a hint to point at those options
being set in rs6000_option_override, then it's fine.
> #define ISA_FUTURE_MASKS_SERVER (ISA_3_0_MASKS_SERVER \
> - | OPTION_MASK_FUTURE \
> - | OPTION_MASK_PREFIXED)
> + | OPTION_MASK_FUTURE)
>
> /* Flags that need to be turned off if -mno-future. */
> #define OTHER_FUTURE_MASKS (OPTION_MASK_PCREL
> \
> --- /tmp/z4Mwhm_rs6000.c 2020-03-27 16:27:05.500619340 -0400
> +++ gcc/config/rs6000/rs6000.c 2020-03-27 16:20:13.066641659
> -0400
> @@ -98,6 +98,12 @@
> #endif
> #endif
>
> +/* Set up the defaults for whether PC-relative addressing is
> supported by the
> + target system. */
> +#ifndef PCREL_SUPPORTED_BY_OS
> +#define PCREL_SUPPORTED_BY_OS 0
> +#endif
> +
> /* Support targetm.vectorize.builtin_mask_for_load. */
> tree altivec_builtin_mask_for_load;
>
> @@ -4014,6 +4020,11 @@ rs6000_option_override_internal (bool gl
> rs6000_isa_flags &= ~OPTION_MASK_FLOAT128_HW;
> }
>
> + /* Enable -mprefixed by default on 64-bit 'future' systems. */
> + if (TARGET_FUTURE && TARGET_POWERPC64
> + && (rs6000_isa_flags_explicit & OPTION_MASK_PREFIXED) == 0)
> + rs6000_isa_flags |= OPTION_MASK_PREFIXED;
> +
> /* -mprefixed (and hence -mpcrel) requires -mcpu=future. */
> if (TARGET_PREFIXED && !TARGET_FUTURE)
> {
> @@ -4175,6 +4186,11 @@ rs6000_option_override_internal (bool gl
> rs6000_isa_flags &= ~OPTION_MASK_PCREL;
> }
>
> + /* If the OS has support for PC-relative relocations, enable it now. */
> + if (PCREL_SUPPORTED_BY_OS
> + && (rs6000_isa_flags_explicit & OPTION_MASK_PCREL) == 0)
> + rs6000_isa_flags |= OPTION_MASK_PCREL;
> +
> if (TARGET_DEBUG_REG || TARGET_DEBUG_TARGET)
> rs6000_print_isa_options (stderr, 0, "after subtarget",
> rs6000_isa_flags);
>
Ok.
thanks
-Will
