From: Eric Botcazou <ebotca...@adacore.com>
Date: Thu, 27 Oct 2011 23:55:00 +0200
>> I quickly tried the patch below, but this does not prevent the
>> transformation.
>
> The quoted code is in copyprop_hardreg_forward_1.
Indeed :-)
This patch below works for the specific test case, and I'll post to
gcc-patches and commit it after regstrapping.
Thanks Eric!
--------------------
Fix illegal register substitutions on big-endian during cprop_reg.
* regcprop.c (copyprop_hardreg_forward_1): Reject the
transformation when we narrow the mode on big endian.
---
gcc/ChangeLog | 5 +++++
gcc/regcprop.c | 8 ++++++++
2 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 403fb60..54e059e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2011-10-27 David S. Miller <da...@davemloft.net>
+
+ * regcprop.c (copyprop_hardreg_forward_1): Reject the
+ transformation when we narrow the mode on big endian.
+
2011-10-27 Jakub Jelinek <ja...@redhat.com>
* config/i386/sse.md (avx_cvtpd2dq256_2, avx_cvttpd2dq256_2,
diff --git a/gcc/regcprop.c b/gcc/regcprop.c
index ad92a64..b0f0343 100644
--- a/gcc/regcprop.c
+++ b/gcc/regcprop.c
@@ -824,6 +824,14 @@ copyprop_hardreg_forward_1 (basic_block bb, struct
value_data *vd)
if (hard_regno_nregs[regno][mode]
> hard_regno_nregs[regno][vd->e[regno].mode])
goto no_move_special_case;
+
+ /* And likewise, if we are narrowing on big endian the
transformation
+ is also invalid. */
+ if (hard_regno_nregs[regno][mode]
+ < hard_regno_nregs[regno][vd->e[regno].mode]
+ && (GET_MODE_SIZE (vd->e[regno].mode) > UNITS_PER_WORD
+ ? WORDS_BIG_ENDIAN : BYTES_BIG_ENDIAN))
+ goto no_move_special_case;
}
/* If the destination is also a register, try to find a source
--
1.7.6.401.g6a319
