[PATCH, ARM] Allow high regs when optimising for size on Thumb-2

[Julian Brown <julian at codesourcery dot com>]

Hi,

This is a size optimisation for Thumb-2. With the patch applied, high
registers are permitted when optimising for size for Thumb-2 (but
still not for Thumb-1). Also SImode loads and stores have their
constraints split into high/low register halves with the high parts not
taken into account when choosing register preferences, to reflect the
greater expense of the high-register alternatives (we don't want to
influence the compiler to use them unless necessary).

Tested on mainline (with flags to generate Thumb-2 code). (We've
also been carrying this in our internal trees for quite a while). OK to
apply?

Julian

ChangeLog

       2007-07-05  Mark Shinwell  <shinwell@codesourcery.com>

        gcc/
        * config/arm/thumb2.md (thumb2_movsi_insn): Split ldr and
        str alternatives according to use of high and low regs.
        * config/arm/vfp.md (thumb2_movsi_vfp): Likewise.
        * config/arm/arm.h (CONDITIONAL_REGISTER_USAGE): Use high
        regs when optimizing for size on Thumb-2.

Index: gcc/config/arm/thumb2.md
===================================================================
--- gcc/config/arm/thumb2.md	(revision 157802)
+++ gcc/config/arm/thumb2.md	(working copy)
@@ -223,9 +223,14 @@
    (set_attr "neg_pool_range" "*,*,*,0,*")]
 )
 
+;; We have two alternatives here for memory loads (and similarly for stores)
+;; to reflect the fact that the permissible constant pool ranges differ
+;; between ldr instructions taking low regs and ldr instructions taking high
+;; regs.  The high register alternatives are not taken into account when
+;; choosing register preferences in order to reflect their expense.
 (define_insn "*thumb2_movsi_insn"
-  [(set (match_operand:SI 0 "nonimmediate_operand" "=rk,r,r,r,rk,m")
-	(match_operand:SI 1 "general_operand"	   "rk ,I,K,j,mi,rk"))]
+  [(set (match_operand:SI 0 "nonimmediate_operand" "=rk,r,r,r,l ,*hk,m,*m")
+	(match_operand:SI 1 "general_operand"	   "rk ,I,K,j,mi,*mi,l,*hk"))]
   "TARGET_THUMB2 && ! TARGET_IWMMXT
    && !(TARGET_HARD_FLOAT && TARGET_VFP)
    && (   register_operand (operands[0], SImode)
@@ -236,11 +241,13 @@
    mvn%?\\t%0, #%B1
    movw%?\\t%0, %1
    ldr%?\\t%0, %1
+   ldr%?\\t%0, %1
+   str%?\\t%1, %0
    str%?\\t%1, %0"
-  [(set_attr "type" "*,*,*,*,load1,store1")
+  [(set_attr "type" "*,*,*,*,load1,load1,store1,store1")
    (set_attr "predicable" "yes")
-   (set_attr "pool_range" "*,*,*,*,4096,*")
-   (set_attr "neg_pool_range" "*,*,*,*,0,*")]
+   (set_attr "pool_range" "*,*,*,*,1020,4096,*,*")
+   (set_attr "neg_pool_range" "*,*,*,*,0,0,*,*")]
 )
 
 (define_insn "tls_load_dot_plus_four"
Index: gcc/config/arm/arm.h
===================================================================
--- gcc/config/arm/arm.h	(revision 157802)
+++ gcc/config/arm/arm.h	(working copy)
@@ -771,12 +771,11 @@ extern int arm_structure_size_boundary;
 	fixed_regs[regno] = call_used_regs[regno] = 1;		\
     }								\
 								\
-  if (TARGET_THUMB && optimize_size)				\
-    {								\
-      /* When optimizing for size, it's better not to use	\
-	 the HI regs, because of the overhead of stacking 	\
-	 them.  */						\
-      /* ??? Is this still true for thumb2?  */			\
+  if (TARGET_THUMB1 && optimize_size)				\
+    {                                                           \
+      /* When optimizing for size on Thumb-1, it's better not	\
+        to use the HI regs, because of the overhead of		\
+        stacking them.  */                                      \
       for (regno = FIRST_HI_REGNUM;				\
 	   regno <= LAST_HI_REGNUM; ++regno)			\
 	fixed_regs[regno] = call_used_regs[regno] = 1;		\
Index: gcc/config/arm/vfp.md
===================================================================
--- gcc/config/arm/vfp.md	(revision 157802)
+++ gcc/config/arm/vfp.md	(working copy)
@@ -86,9 +86,11 @@
    (set_attr "neg_pool_range" "*,*,*,*,4084,*,*,*,*,1008,*")]
 )
 
+;; See thumb2.md:thumb2_movsi_insn for an explanation of the split
+;; high/low register alternatives for loads and stores here.
 (define_insn "*thumb2_movsi_vfp"
-  [(set (match_operand:SI 0 "nonimmediate_operand" "=rk,r,r,r,rk,m,*t,r, *t,*t, *Uv")
-      (match_operand:SI 1 "general_operand"	   "rk, I,K,j,mi,rk,r,*t,*t,*Uvi,*t"))]
+  [(set (match_operand:SI 0 "nonimmediate_operand" "=rk,r,r,r,l,*hk,m,*m,*t,r, *t,*t, *Uv")
+      (match_operand:SI 1 "general_operand"	   "rk, I,K,j,mi,*mi,l,*hk,r,*t,*t,*Uvi,*t"))]
   "TARGET_THUMB2 && TARGET_VFP && TARGET_HARD_FLOAT
    && (   s_register_operand (operands[0], SImode)
        || s_register_operand (operands[1], SImode))"
@@ -102,25 +104,27 @@
     case 3:
       return \"movw%?\\t%0, %1\";
     case 4:
-      return \"ldr%?\\t%0, %1\";
     case 5:
-      return \"str%?\\t%1, %0\";
+      return \"ldr%?\\t%0, %1\";
     case 6:
-      return \"fmsr%?\\t%0, %1\\t%@ int\";
     case 7:
-      return \"fmrs%?\\t%0, %1\\t%@ int\";
+      return \"str%?\\t%1, %0\";
     case 8:
+      return \"fmsr%?\\t%0, %1\\t%@ int\";
+    case 9:
+      return \"fmrs%?\\t%0, %1\\t%@ int\";
+    case 10:
       return \"fcpys%?\\t%0, %1\\t%@ int\";
-    case 9: case 10:
+    case 11: case 12:
       return output_move_vfp (operands);
     default:
       gcc_unreachable ();
     }
   "
   [(set_attr "predicable" "yes")
-   (set_attr "type" "*,*,*,*,load1,store1,r_2_f,f_2_r,fcpys,f_load,f_store")
-   (set_attr "pool_range"     "*,*,*,*,4096,*,*,*,*,1020,*")
-   (set_attr "neg_pool_range" "*,*,*,*,   0,*,*,*,*,1008,*")]
+   (set_attr "type" "*,*,*,*,load1,load1,store1,store1,r_2_f,f_2_r,fcpys,f_load,f_store")
+   (set_attr "pool_range"     "*,*,*,*,1020,4096,*,*,*,*,*,1020,*")
+   (set_attr "neg_pool_range" "*,*,*,*,   0,   0,*,*,*,*,*,1008,*")]
 )