Commit message:
Enable -mpcrel for -mcpu=future if it is allowed by the ABI.
2020-04-06 Michael Meissner <meiss...@linux.ibm.com>
* config/rs6000/linux64.h (PCREL_SUPPORTED_BY_OS): Enable
prefixed PC-relative addressing if the ABI supports it.
* config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): Do not
set OPTION_MASK_PREFIXED here.
* config/rs6000/rs6000.c (rs6000_option_override_internal): Enable
OPTION_MASK_PREFIXED and OPTION_MASK_PCREL on -mcpu=future by
default if the current ABI allows the options.
I tested this on a little endian PowerPC power8 system, doing bootstrap and
make check. There were no regressions. I tested by hand the various
conditions where -mpcrel is not enabled, and they all used the normal power9
TOC references.
-mcpu=power9 generates TOC;
-mcpu=future -mcmodel=large generates TOC;
-mcpu=future -mcmode=small generates TOC;
-mcpu=future -mno-prefixed generates TOC;
-mcpu=future -mno-pcrel generates TOC;
-mcpu=future generates PC-relative.
--- /tmp/apbaWN_linux64.h 2020-04-03 17:15:05.059677000 -0400
+++ gcc/config/rs6000/linux64.h 2020-04-03 17:01:05.580426937 -0400
@@ -640,3 +640,10 @@ extern int dot_symbols;
enabling the __float128 keyword. */
#undef TARGET_FLOAT128_ENABLE_TYPE
#define TARGET_FLOAT128_ENABLE_TYPE 1
+
+/* Enable using prefixed PC-relative addressing on the 'future' machine if the
+ ABI supports it. The ELF v2 ABI only supports PC-relative relocations for
+ the medium code model. */
+#define PCREL_SUPPORTED_BY_OS (TARGET_FUTURE && TARGET_PREFIXED \
+ && ELFv2_ABI_CHECK \
+ && (TARGET_CMODEL == CMODEL_MEDIUM))
--- /tmp/XzRKno_rs6000-cpus.def 2020-04-03 17:15:05.068676928 -0400
+++ gcc/config/rs6000/rs6000-cpus.def 2020-04-03 17:00:50.115550614 -0400
@@ -75,10 +75,14 @@
| 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. Do not set OPTION_MASK_PREFIXED
+ or OPTION_MASK_PCREL here. Those options are enabled in the function
+ rs6000_option_override if the ABI supports them. */
#define ISA_FUTURE_MASKS_SERVER (ISA_3_0_MASKS_SERVER
\
- | OPTION_MASK_FUTURE \
+ | OPTION_MASK_FUTURE)
+
+/* Flags that need to be turned off if -mno-future. */
+#define OTHER_FUTURE_MASKS (OPTION_MASK_PCREL \
| OPTION_MASK_PREFIXED)
/* Flags that need to be turned off if -mno-future. */
--- /tmp/nyxSRY_rs6000.c 2020-04-03 17:15:05.081676823 -0400
+++ gcc/config/rs6000/rs6000.c 2020-04-03 17:03:19.846353197 -0400
@@ -4020,6 +4020,12 @@ 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)
{
@@ -4171,6 +4177,14 @@ rs6000_option_override_internal (bool gl
SUB3TARGET_OVERRIDE_OPTIONS;
#endif
+#ifdef PCREL_SUPPORTED_BY_OS
+ /* If the ABI has support for PC-relative relocations, enable it by
+ default. */
+ if (PCREL_SUPPORTED_BY_OS
+ && (rs6000_isa_flags_explicit & OPTION_MASK_PCREL) == 0)
+ rs6000_isa_flags |= OPTION_MASK_PCREL;
+#endif
+
/* -mpcrel requires -mcmodel=medium, but we can't check TARGET_CMODEL until
after the subtarget override options are done. */
if (TARGET_PCREL && TARGET_CMODEL != CMODEL_MEDIUM)
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meiss...@linux.ibm.com, phone: +1 (978) 899-4797
