Hi,
This patch fixes a combiner bug in simplify_set which calls
CANNOT_CHANGE_MODE_CLASS with wrong mode params.
It occurs when trying to simplify paradoxical subregs of hw regs (whose
natural mode is lower than a word).
In fact, changing from (set x:m1 (subreg:m1 (op:m2))) to (set (subreg:m2
x) op2) is valid if REG_CANNOT_CHANGE_MODE_P (x, m1, m2) is false
and REG_CANNOT_CHANGE_MODE_P (x, GET_MODE (src), GET_MODE (SUBREG_REG
(src))
See:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79279
Validated on a private target,
bootstraped on x86_64-pc-linux-gnu, but I'm not sure which target is the
most relevant for this patch though ...
OK to commit?
Aurélien
Changelog:
2017-01-27 Aurelien Buhrig <aurelien.buhrig....@gmail.com>
* combine.c (simplify_set): Fix call to REG_CANNOT_CHANGE_MODE_CLASS_P
Index: gcc/combine.c
===================================================================
--- gcc/combine.c (revision 244978)
+++ gcc/combine.c (working copy)
@@ -6796,8 +6796,8 @@
#ifdef CANNOT_CHANGE_MODE_CLASS
&& ! (REG_P (dest) && REGNO (dest) < FIRST_PSEUDO_REGISTER
&& REG_CANNOT_CHANGE_MODE_P (REGNO (dest),
- GET_MODE (SUBREG_REG (src)),
- GET_MODE (src)))
+ GET_MODE (src),
+ GET_MODE (SUBREG_REG (src))))
#endif
&& (REG_P (dest)
|| (GET_CODE (dest) == SUBREG
