[Cleaning this thread up to submit patch again, with better explanation] This patch causes subreg_get_info() to exit early in the simple cases where we are extracting a whole register from a multi register.
In aarch64 for Big Endian we were producing a subreg of a OImode (256bits)
from a CImode (384bits) This would hit the following assert in
subreg_get_info:
gcc_assert ((GET_MODE_SIZE (xmode) % GET_MODE_SIZE (ymode)) == 0);
This is a rule we should be able to relax a little - if the subreg we want
fits into a whole register then this is a valid result and can be easily
detected earlier in the function.
This has the bonus that we should be slightly reducing the execution time
for more common cases, for example a subreg of 64bits from 256bits.
This patch is required for the second part of the patch, which is aarch64
specific, and fixes up aarch64 Big Endian movoi/ci/xi. This second part
has already been approved.
This patch will apply cleanly by itself and no regressions were seen when
testing aarch64 and x86_64 on make check.
Cheers,
Alan
Changelog:
2014-11-14 Alan Hayward <alan.hayw...@arm.com>
* rtlanal.c
(subreg_get_info): Exit early for simple and common cases
---
gcc/rtlanal.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index c9bf69c..a3f7b78 100644
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -3561,6 +3561,19 @@ subreg_get_info (unsigned int xregno, machine_mode
xmode,
info->offset = offset / regsize_xmode;
return;
}
+ /* Quick exit for the simple and common case of extracting whole
+ subregisters from a multiregister value. */
+ if (!rknown
+ && WORDS_BIG_ENDIAN == REG_WORDS_BIG_ENDIAN
+ && regsize_xmode == regsize_ymode
+ && (offset % regsize_ymode) == 0)
+ {
+ info->representable_p = true;
+ info->nregs = nregs_ymode;
+ info->offset = offset / regsize_ymode;
+ gcc_assert (info->offset + info->nregs <= nregs_xmode);
+ return;
+ }
}
/* Lowpart subregs are otherwise valid. */
--
1.9.1
0001-BE-fix-load-stores.-Common-code.patch
Description: Binary data
