[PATCH, ARM] Tune thumb1_size_rtx_costs

[Zhenqiang Chen]

Hi,

Currently most thumb1_size_rtx_costs are "guessed" from performance view,
not size.

The patch adjusts some of them according the instruction patterns defined in
thumb1.md. It also replaces several hard coded "4" to COSTS_N_INSNS (1).

No make check regression for Cortex-M0 on qemu.
For Cortex-M0 text code size, it reduces 0.15% for CSiBE, 0.59% for
coremark, 0.13% for dhrystone, 0.14% for eembc_v1 and 0.31% for eembc-v2.

OK for trunk?

Thanks!
-Zhenqiang

ChangeLog:
2014-09-10  Zhenqiang Chen  <zhenqiang.c...@arm.com>

        * config/arm/arm.c: #include "tm-constrs.h"
        (thumb1_size_rtx_costs): Adjust rtx costs.

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 11e0655..a19e15c 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -62,6 +62,7 @@
 #include "dumpfile.h"
 #include "gimple-expr.h"
 #include "builtins.h"
+#include "tm-constrs.h"
 
 /* Forward definitions of types.  */
 typedef struct minipool_node    Mnode;
@@ -8888,9 +8889,11 @@ thumb1_size_rtx_costs (rtx x, enum rtx_code code,
enum rtx_code outer)
       /* A SET doesn't have a mode, so let's look at the SET_DEST to get
         the mode.  */
       words = ARM_NUM_INTS (GET_MODE_SIZE (GET_MODE (SET_DEST (x))));
-      return (COSTS_N_INSNS (words)
-              + 4 * ((MEM_P (SET_SRC (x)))
-                     + MEM_P (SET_DEST (x))));
+      return COSTS_N_INSNS (words)
+            + COSTS_N_INSNS (1) * (satisfies_constraint_J (SET_SRC (x))
+                                   || satisfies_constraint_K (SET_SRC (x))
+                                      /* thumb1_movdi_insn.  */
+                                   || ((words > 1) && MEM_P (SET_SRC
(x))));
 
     case CONST_INT:
       if (outer == SET)
@@ -8943,16 +8946,14 @@ thumb1_size_rtx_costs (rtx x, enum rtx_code code,
enum rtx_code outer)
     case AND:
     case XOR:
     case IOR:
-      /* XXX guess.  */
-      return 8;
+      return COSTS_N_INSNS (1);
 
     case MEM:
-      /* XXX another guess.  */
-      /* Memory costs quite a lot for the first word, but subsequent words
-         load at the equivalent of a single insn each.  */
-      return (10 + 4 * ((GET_MODE_SIZE (mode) - 1) / UNITS_PER_WORD)
+      return (COSTS_N_INSNS (1)
+             + COSTS_N_INSNS (1)
+               * ((GET_MODE_SIZE (mode) - 1) / UNITS_PER_WORD)
               + ((GET_CODE (x) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P
(x))
-                 ? 4 : 0));
+                 ? COSTS_N_INSNS (1) : 0));
 
     case IF_THEN_ELSE:
       /* XXX a guess.  */