Hi,
The problem here is that adjust_address returns the same rtl as we
already have a BLKmode; mips_block_move_straight pass a BLKmode MEM to
mips_expand_ext_as_unaligned_load.
The following patch fixes the problem by copying the MEM after calling
adjust_address. This does increase garbage slightly but not enough to
take a notice. I could only get this to expose after improving
mips_block_move_straight but it could show up in otherwise. The
testcase where it showed has already been committed as
testsuite/gcc.c-torture/compile/20120524-1.c .
OK? Bootstrapped and tested on mips64-linux-gnu with no regressions.
ChangeLog:
* config/mips/mips.c (mips_get_unaligned_mem): Copy *op after calling
adjust_address.
Index: config/mips/mips.c
===================================================================
--- config/mips/mips.c (revision 189542)
+++ config/mips/mips.c (working copy)
@@ -7220,6 +7220,8 @@ mips_get_unaligned_mem (rtx *op, HOST_WI
/* Adjust *OP to refer to the whole field. This also has the effect
of legitimizing *OP's address for BLKmode, possibly simplifying it. */
*op = adjust_address (*op, BLKmode, 0);
+ /* Copy the RTX as adjust_address might return the original rtl. */
+ *op = copy_rtx (*op);
set_mem_size (*op, width / BITS_PER_UNIT);
/* Get references to both ends of the field. We deliberately don't
