diff options
Diffstat (limited to 'gcc/config/rs6000/rs6000.c')
| -rw-r--r-- | gcc/config/rs6000/rs6000.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index 267a161..ea5c010 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -1316,6 +1316,8 @@ rs6000_override_options (const char *default_cpu) #if TARGET_MACHO darwin_one_byte_bool = ""; #endif + /* Default to natural alignment, for better performance. */ + rs6000_alignment_flags = MASK_ALIGN_NATURAL; } /* Handle -mabi= options. */ @@ -1684,7 +1686,16 @@ rs6000_parse_alignment_option (void) if (rs6000_alignment_string == 0) return; else if (! strcmp (rs6000_alignment_string, "power")) - rs6000_alignment_flags = MASK_ALIGN_POWER; + { + /* On 64-bit Darwin, power alignment is ABI-incompatible with + some C library functions, so warn about it. The flag may be + useful for performance studies from time to time though, so + don't disable it entirely. */ + if (DEFAULT_ABI == ABI_DARWIN && TARGET_64BIT) + warning ("-malign-power is not supported for 64-bit Darwin;" + " it is incompatible with the installed C and C++ libraries"); + rs6000_alignment_flags = MASK_ALIGN_POWER; + } else if (! strcmp (rs6000_alignment_string, "natural")) rs6000_alignment_flags = MASK_ALIGN_NATURAL; else |