------- Additional Comments From aoliva at gcc dot gnu dot org 2005-03-07
21:57 -------
Subject: [PR target/20126, RFC] loop DEST_ADDR biv replacement may fail
loop attempts to eliminate a biv represented by a pseudo in favor of a
giv represented by (plus (reg) (const_int -1)). Unfortunately, the
biv pseudo appears in an insn that doesn't accept anything but a
register, so validate_change fails and the error goes unnoticed.
The patch below fixes the problem and passed bootstrap on
x86_64-linux-gnu (testing still pending), but I'm not very comfortable
with the use of location for the assignment. Is this a safe change?
Any loop experts around willing to take a second look on this? Thanks
in advance,
Index: gcc/ChangeLog
from Alexandre Oliva <[EMAIL PROTECTED]>
PR target/20126
* loop.c (loop_givs_rescan): If replacement of DEST_ADDR failed,
set the original address pseudo to the correct value before the
original insn and leave the insn alone.
Index: gcc/loop.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/loop.c,v
retrieving revision 1.522
diff -u -p -r1.522 loop.c
--- gcc/loop.c 17 Jan 2005 08:46:15 -0000 1.522
+++ gcc/loop.c 7 Mar 2005 21:37:43 -0000
@@ -5470,9 +5470,16 @@ loop_givs_rescan (struct loop *loop, str
mark_reg_pointer (v->new_reg, 0);
if (v->giv_type == DEST_ADDR)
- /* Store reduced reg as the address in the memref where we found
- this giv. */
- validate_change (v->insn, v->location, v->new_reg, 0);
+ {
+ /* Store reduced reg as the address in the memref where we found
+ this giv. */
+ if (! validate_change (v->insn, v->location, v->new_reg, 0))
+ /* Not replaceable; emit an insn to set the original giv reg from
+ the reduced giv. */
+ v->insn = loop_insn_emit_before (loop, 0, v->insn,
+ gen_move_insn (*v->location,
+ v->new_reg));
+ }
else if (v->replaceable)
{
reg_map[REGNO (v->dest_reg)] = v->new_reg;
--
Alexandre Oliva http://www.ic.unicamp.br/~oliva/
Red Hat Compiler Engineer [EMAIL PROTECTED], gcc.gnu.org}
Free Software Evangelist [EMAIL PROTECTED], gnu.org}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20126
