Turn on -mpcrel by default for -mcpu=future
I reworked the patches based on your comments:
1) I removed the check for 64-bit;
2) I now set the prefixed and PC-relative bits on by default;
3) I removed the #if around the test, and provided a definition earlier;
5) I removed the #undef in linux64.h for PCREL_SUPPORTED_BY_OS.
I have also simplified the check for prefixed and PC-relative, so that the
prefix check only checks for prefixed, and the PC-relative check is separate.
I have checked against the trunk, doing bootstrap builds and make check, and
there were no regressions. Can I check this patch into the master branch?
2020-04-21 Michael Meissner
* config/rs6000/linux64.h (PCREL_SUPPORTED_BY_OS): Define to
enable PC-relative addressing for -mcpu=future.
* config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): Move
after OTHER_FUTURE_MASKS. Use OTHER_FUTURE_MASKS.
* config/rs6000/rs6000.c (PCREL_SUPPORTED_BY_OS): If not defined,
suppress PC-relative addressing.
(rs6000_option_override_internal): Split up error messages
checking for -mprefixed and -mpcrel. Enable -mpcrel if the target
system supports it.
--- /tmp/ud7l8s_linux64.h 2020-04-21 16:09:26.761209165 -0400
+++ gcc/config/rs6000/linux64.h 2020-04-21 16:04:59.432652447 -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/g2yeWR_rs6000-cpus.def 2020-04-21 16:09:26.772209188 -0400
+++ gcc/config/rs6000/rs6000-cpus.def 2020-04-21 16:04:59.433652450 -0400
@@ -75,16 +75,15 @@
| OPTION_MASK_P8_VECTOR\
| OPTION_MASK_P9_VECTOR)
-/* Support for a future processor's features. Do not enable -mpcrel until it
- is fully functional. */
-#define ISA_FUTURE_MASKS_SERVER(ISA_3_0_MASKS_SERVER
\
-| OPTION_MASK_FUTURE \
-| OPTION_MASK_PREFIXED)
-
/* Flags that need to be turned off if -mno-future. */
#define OTHER_FUTURE_MASKS (OPTION_MASK_PCREL \
| OPTION_MASK_PREFIXED)
+/* Support for a future processor's features. */
+#define ISA_FUTURE_MASKS_SERVER(ISA_3_0_MASKS_SERVER
\
+| OPTION_MASK_FUTURE \
+| OTHER_FUTURE_MASKS)
+
/* Flags that need to be turned off if -mno-power9-vector. */
#define OTHER_P9_VECTOR_MASKS (OPTION_MASK_FLOAT128_HW\
| OPTION_MASK_P9_MINMAX)
--- /tmp/KhNyMg_rs6000.c2020-04-21 16:09:26.785209215 -0400
+++ gcc/config/rs6000/rs6000.c 2020-04-21 16:09:20.579196291 -0400
@@ -98,6 +98,11 @@
#endif
#endif
+/* Don't enable PC-relative addressing if the target does not support it. */
+#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;
@@ -4024,15 +4029,17 @@ rs6000_option_override_internal (bool gl
rs6000_isa_flags &= ~OPTION_MASK_FLOAT128_HW;
}
- /* -mprefixed (and hence -mpcrel) requires -mcpu=future. */
- if (TARGET_PREFIXED && !TARGET_FUTURE)
+ /* Enable -mprefixed by default on 'future' systems. */
+ if (TARGET_FUTURE && (rs6000_isa_flags_explicit & OPTION_MASK_PREFIXED) == 0)
+rs6000_isa_flags |= OPTION_MASK_PREFIXED;
+
+ /* -mprefixed requires -mcpu=future. */
+ else if (TARGET_PREFIXED && !TARGET_FUTURE)
{
- if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
- error ("%qs requires %qs", "-mpcrel", "-mcpu=future");
- else if ((rs6000_isa_flags_explicit & OPTION_MASK_PREFIXED) != 0)
+ if ((rs6000_isa_flags_explicit & OPTION_MASK_PREFIXED) != 0)
error ("%qs requires %qs", "-mprefixed", "-mcpu=future");
- rs6000_isa_flags &= ~(OPTION_MASK_PCREL | OPTION_MASK_PREFIXED);
+ rs6000_isa_flags &= ~OPTION_MASK_PREFIXED;
}
/* -mpcrel requires prefixed load/store addressing. */
@@ -4175,9 +4182,16 @@ rs6000_option_override_internal (bool gl
SUB3TARGET_OVERRIDE_OPTIONS;
#endif
+ /* If the ABI has support for PC-relative relocations, enable it by default.
+ This test depends on the sub-target tests above setting the code model to
+ medium for ELF v2 systems. */
+ if (PCREL_SUPPORTED_BY_OS
+
