http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45051
Ian Bolton <ibolton at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
CC| |ibolton at gcc dot gnu.org
Resolution|FIXED |
--- Comment #7 from Ian Bolton <ibolton at gcc dot gnu.org> 2010-12-22 16:23:21
UTC ---
(In reply to comment #5)
> Assuming fixed and closing. Please reopen if you still have a problem.
This patch has caused SpecCPU2000 Ammp to fail for ARM -O3 thumb.
I assume the patch was meant to prevent deletions that shouldn't occur. This
might be what happens for the original symptomatic test, but I am now seeing
extra deletions that shouldn't happen for Ammp.
For example, without this patch, you get these insns somewhere in the ira dump
for mm_fv_update_nonbon() from rectmm.c:
(insn 3163 3161 3164 107 rectmm.c:1041 (set (reg:SI 1 r1)
(plus:SI (reg:SI 1 r1)
(const_int 280 [0x118]))) 4 {*arm_addsi3} (nil))
(insn 3164 3163 1730 107 rectmm.c:1041 (set (reg:SI 3 r3)
(reg:SI 1 r1)) 586 {*thumb2_movsi_vfp} (nil))
With the patch, you lose the add and just get this:
(insn 3164 3161 1730 107 rectmm.c:1041 (set (reg:SI 3 r3)
(reg:SI 1 r1)) 586 {*thumb2_movsi_vfp} (nil))
The incrementing of r1 is perfectly legitimate and useful and removing it is a
bug. Other increments of r9, ip, r0 and r3 are also lost.
I think the issue might be that reg_mentioned_p() considers output registers to
have been "mentioned", whereas the refers_to_regno_p() does not consider an
output register to have been "referred to". I can see the problem with only
using reg_mentioned_p() because it doesn't handle subregs, but there is also a
problem with only using refers_to_regno_p(), as we can see with this segfault
in Ammp.
I therefore wonder if the fix might be this:
Index: gcc/reload1.c
===================================================================
--- gcc/reload1.c (revision 168082)
+++ gcc/reload1.c (working copy)
@@ -8395,7 +8395,8 @@ delete_output_reload (rtx insn, int j, i
if (NOTE_INSN_BASIC_BLOCK_P (i1))
return;
if ((NONJUMP_INSN_P (i1) || CALL_P (i1))
- && refers_to_regno_p (regno, regno + nregs, PATTERN (i1), NULL))
+ && (refers_to_regno_p (regno, regno + nregs, PATTERN (i1), NULL)
+ || reg_mentioned_p (reg, PATTERN (i1))))
{
/* If this is USE in front of INSN, we only have to check that
there are no more references than accounted for by inheritance.
*/
I am heading off for Christmas vacation shortly, so cannot look into this any
further, but I wanted to record my findings so far publicly. Apologies if
there is missing information. I return to work Jan 4th.
