[PATCH] Fix illegal register substitutions on big-endian during cprop_reg.

[David Miller]

As discussed in the thread starting at:

http://gcc.gnu.org/ml/gcc/2011-10/msg00478.html

We need to make the tests done in copyprop_hardreg_forward_1()
match those performed in copy_value(), and in particular make
sure that if we are narrowing the mode on big-endian we do
not perform the substitution.

Committed to trunk.

gcc/

        * 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