[Patch, ARM][6/8] Epilogue in RTL: simple return

[Greta Yorsh]

Add a new parameter to the function output_return_instruction to handle
simple cases of return when no epilogue needs to be printed out.

ChangeLog:

gcc

2012-05-31  Ian Bolton  <ian.bol...@arm.com>
            Sameera Deshpande  <sameera.deshpa...@arm.com>
            Greta Yorsh  <greta.yo...@arm.com>

        * config/arm/arm-protos.h (output_return_instruction): New
parameter.
        * config/arm/arm.c (output_return_instruction): New parameter.
        * config/arm/arm.md (arm_simple_return): New pattern.
        (arm_return, cond_return, cond_return_inverted): Add new arguments.
        * config/arm/thumb2.md (thumb2_return): Update condition and code.

diff --git a/gcc/config/arm/arm-protos.h b/gcc/config/arm/arm-protos.h
index f61feef..01cd794 100644
--- a/gcc/config/arm/arm-protos.h
+++ b/gcc/config/arm/arm-protos.h
@@ -148,7 +148,7 @@ extern int arm_address_offset_is_imm (rtx);
 extern const char *output_add_immediate (rtx *);
 extern const char *arithmetic_instr (rtx, int);
 extern void output_ascii_pseudo_op (FILE *, const unsigned char *, int);
-extern const char *output_return_instruction (rtx, int, int);
+extern const char *output_return_instruction (rtx, int, int, int);
 extern void arm_poke_function_name (FILE *, const char *);
 extern void arm_final_prescan_insn (rtx);
 extern int arm_debugger_arg_offset (int, rtx);
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index c8642e2..e7a74e0 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -15592,9 +15592,11 @@ arm_get_vfp_saved_size (void)
 
 
 /* Generate a function exit sequence.  If REALLY_RETURN is false, then do
-   everything bar the final return instruction.  */
+   everything bar the final return instruction.  If simple_return is true,
+   then do not output epilogue, because it has already been emitted in RTL.  */
 const char *
-output_return_instruction (rtx operand, int really_return, int reverse)
+output_return_instruction (rtx operand, int really_return, int reverse,
+                           int simple_return)
 {
   char conditional[10];
   char instr[100];
@@ -15637,7 +15639,7 @@ output_return_instruction (rtx operand, int 
really_return, int reverse)
   offsets = arm_get_frame_offsets ();
   live_regs_mask = offsets->saved_regs_mask;
 
-  if (live_regs_mask)
+  if (!simple_return && live_regs_mask)
     {
       const char * return_reg;
 
@@ -15765,7 +15767,7 @@ output_return_instruction (rtx operand, int 
really_return, int reverse)
        {
          /* The return has already been handled
             by loading the LR into the PC.  */
-         really_return = 0;
+          return "";
        }
     }
 
diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index d1c1894..867dcbe 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -8597,7 +8597,7 @@
         arm_ccfsm_state += 2;
         return \"\";
       }
-    return output_return_instruction (const_true_rtx, TRUE, FALSE);
+    return output_return_instruction (const_true_rtx, TRUE, FALSE, FALSE);
   }"
   [(set_attr "type" "load1")
    (set_attr "length" "12")
@@ -8618,7 +8618,7 @@
         arm_ccfsm_state += 2;
         return \"\";
       }
-    return output_return_instruction (operands[0], TRUE, FALSE);
+    return output_return_instruction (operands[0], TRUE, FALSE, FALSE);
   }"
   [(set_attr "conds" "use")
    (set_attr "length" "12")
@@ -8639,13 +8639,30 @@
         arm_ccfsm_state += 2;
         return \"\";
       }
-    return output_return_instruction (operands[0], TRUE, TRUE);
+    return output_return_instruction (operands[0], TRUE, TRUE, FALSE);
   }"
   [(set_attr "conds" "use")
    (set_attr "length" "12")
    (set_attr "type" "load1")]
 )
 
+(define_insn "*arm_simple_return"
+  [(simple_return)]
+  "TARGET_ARM"
+  "*
+  {
+    if (arm_ccfsm_state == 2)
+      {
+        arm_ccfsm_state += 2;
+        return \"\";
+      }
+    return output_return_instruction (const_true_rtx, TRUE, FALSE, TRUE);
+  }"
+  [(set_attr "type" "branch")
+   (set_attr "length" "4")
+   (set_attr "predicable" "yes")]
+)
+
 ;; Generate a sequence of instructions to determine if the processor is
 ;; in 26-bit or 32-bit mode, and return the appropriate return address
 ;; mask.
diff --git a/gcc/config/arm/thumb2.md b/gcc/config/arm/thumb2.md
index 39a2138..b7a8423 100644
--- a/gcc/config/arm/thumb2.md
+++ b/gcc/config/arm/thumb2.md
@@ -635,17 +635,12 @@
    (set_attr "length" "20")]
 )
 
-;; Note: this is not predicable, to avoid issues with linker-generated
-;; interworking stubs.
 (define_insn "*thumb2_return"
-  [(return)]
-  "TARGET_THUMB2 && USE_RETURN_INSN (FALSE)"
-  "*
-  {
-    return output_return_instruction (const_true_rtx, TRUE, FALSE);
-  }"
-  [(set_attr "type" "load1")
-   (set_attr "length" "12")]
+  [(simple_return)]
+  "TARGET_THUMB2"
+  "* return output_return_instruction (const_true_rtx, TRUE, FALSE, TRUE);"
+  [(set_attr "type" "branch")
+   (set_attr "length" "4")]
 )
 
 (define_insn_and_split "thumb2_eh_return"