diff mbox

[MIPS,committed] Adding missing register move costs for M16_REGS

Message ID 87txcxt5zc.fsf@talisman.default
State New
Headers show

Commit Message

Richard Sandiford Jan. 21, 2014, 8:49 p.m. UTC 
This patch fixes a stupid oversight in:

2008-10-24  Richard Sandiford  <rdsandiford@googlemail.com>

	* config/mips/mips.c (mips_canonicalize_move_class): New function.
	(mips_move_to_gpr_cost): Likewise.
	(mips_move_from_gpr_cost): Likewise.
	(mips_register_move_cost): Make more fine-grained.

The idea was to handle the various subclasses and union classes correctly,
but I missed out the case for M16_REGS.  This meant that some MIPS16 moves
were wrongly getting a cost of 0 instead of the correct cost of 2.
That in turn caused a segfault when dividing by a register cost in
gcc.dg/pr37156.c.

I tried to see what effect this patch had on code size for -Os -mips16,
but as usual it was a case of some better, some worse.  The overall
change was of the order of 0.01%.  As a point of comparison I tried
disabling Steve's patch to fix the $t registers and as expected the
results were more consistently worse.

Anyway, it's wrong to return 0 as a move cost for non-union classes,
so we need something like this whatever happens.  It probably doesn't
make much sense to tune the costs further with reload instead of LRA.

Tested on mips64-linux-gnu and applied.

Thanks,
Richard


gcc/
	* config/mips/mips.c (mips_move_to_gpr_cost): Add M16_REGS case.
	(mips_move_from_gpr_cost): Likewise.
diff mbox

Patch

Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c	2014-01-21 20:38:01.864324981 +0000
+++ gcc/config/mips/mips.c	2014-01-21 20:38:53.734788910 +0000
@@ -11883,6 +11883,7 @@  mips_move_to_gpr_cost (enum machine_mode
 {
   switch (from)
     {
+    case M16_REGS:
     case GENERAL_REGS:
       /* A MIPS16 MOVE instruction, or a non-MIPS16 MOVE macro.  */
       return 2;
@@ -11919,6 +11920,7 @@  mips_move_from_gpr_cost (enum machine_mo
 {
   switch (to)
     {
+    case M16_REGS:
     case GENERAL_REGS:
       /* A MIPS16 MOVE instruction, or a non-MIPS16 MOVE macro.  */
       return 2;