[committed] Add SET rtx costs for MIPS

[Richard Sandiford]

This patch adds SET rtx costs to MIPS.  Since "FPR modes" and "GPR modes"
aren't tieable, the effect is to restore the original lower-subreg behaviour
of splitting all multiword modes.

Tested by setting LOG_COSTS to 1 and checking that the costs looked sensible.
Also tested by compiling cc1 .ii files for -mabi=n32, -mabi=64, -mabi=32
and -mabi=32 -mfp64.  The output was the same as when FORCE_LOWERING was
set to 1, but different from unmodified trunk.  Applied.

Richard


gcc/
        * config/mips/mips.c (mips_set_reg_reg_piece_cost): New function.
        (mips_set_reg_reg_cost): Likewise.
        (mips_rtx_costs): Handle SET.

Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c      2012-05-06 13:47:49.000000000 +0100
+++ gcc/config/mips/mips.c      2012-05-06 14:10:25.636105001 +0100
@@ -3490,6 +3490,37 @@ mips_zero_extend_cost (enum machine_mode
   return COSTS_N_INSNS (1);
 }
 
+/* Return the cost of moving between two registers of mode MODE,
+   assuming that the move will be in pieces of at most UNITS bytes.  */
+
+static int
+mips_set_reg_reg_piece_cost (enum machine_mode mode, unsigned int units)
+{
+  return COSTS_N_INSNS ((GET_MODE_SIZE (mode) + units - 1) / units);
+}
+
+/* Return the cost of moving between two registers of mode MODE.  */
+
+static int
+mips_set_reg_reg_cost (enum machine_mode mode)
+{
+  switch (GET_MODE_CLASS (mode))
+    {
+    case MODE_CC:
+      return mips_set_reg_reg_piece_cost (mode, GET_MODE_SIZE (CCmode));
+
+    case MODE_FLOAT:
+    case MODE_COMPLEX_FLOAT:
+    case MODE_VECTOR_FLOAT:
+      if (TARGET_HARD_FLOAT)
+       return mips_set_reg_reg_piece_cost (mode, UNITS_PER_HWFPVALUE);
+      /* Fall through */
+
+    default:
+      return mips_set_reg_reg_piece_cost (mode, UNITS_PER_WORD);
+    }
+}
+
 /* Implement TARGET_RTX_COSTS.  */
 
 static bool
@@ -3877,6 +3908,15 @@ mips_rtx_costs (rtx x, int code, int out
       *total = mips_cost->fp_add;
       return false;
 
+    case SET:
+      if (register_operand (SET_DEST (x), VOIDmode)
+         && reg_or_0_operand (SET_SRC (x), VOIDmode))
+       {
+         *total = mips_set_reg_reg_cost (GET_MODE (SET_DEST (x)));
+         return true;
+       }
+      return false;
+
     default:
       return false;
     }