https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67609
--- Comment #44 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to rsand...@gcc.gnu.org from comment #43)
> FWIW, the proposed patch for PR69577 fixes this testcase
> with the aarch64_cannot_change_mode_class change reverted.
> The code quality looks slightly better too.
The same is true with x86_64. Following revert causes no testsuite regressions:
--cut here--
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 233079)
+++ config/i386/i386.c (working copy)
@@ -43283,25 +43283,12 @@ ix86_cannot_change_mode_class (machine_mode from,
if (MAYBE_SSE_CLASS_P (regclass) || MAYBE_MMX_CLASS_P (regclass))
{
- int from_size = GET_MODE_SIZE (from);
- int to_size = GET_MODE_SIZE (to);
-
/* Vector registers do not support QI or HImode loads. If we don't
disallow a change to these modes, reload will assume it's ok to
drop the subreg from (subreg:SI (reg:HI 100) 0). This affects
the vec_dupv4hi pattern. */
- if (from_size < 4)
+ if (GET_MODE_SIZE (from) < 4)
return true;
-
- /* Further, we cannot allow word_mode subregs of full vector modes.
- Otherwise the middle-end will assume it's ok to store to
- (subreg:DI (reg:TI 100) 0) in order to modify only the low 64 bits
- of the 128-bit register. However, after reload the subreg will
- be dropped leaving a plain DImode store. This is indistinguishable
- from a "normal" DImode move, and so we're justified to use movsd,
- which modifies the entire 128-bit register. */
- if (to_size == UNITS_PER_WORD && from_size > UNITS_PER_WORD)
- return true;
}
return false;
--cut here--
