Enable fuse-caller-save on self-recursive functions

2014-07-09  Tom de Vries  <tom@codesourcery.com>

	* final.c (get_call_fndecl): Declare.
	(self_recursive_call_p): New function.
	(collect_fn_hard_reg_usage): Handle self-recursive function calls.

	* gcc.target/i386/fuse-caller-save-rec.c: New test.

From-SVN: r212409

gcc/final.c

@@ -225,6 +225,7 @@ static int final_addr_vec_align (rtx);
 #endif
 static int align_fuzz (rtx, rtx, int, unsigned);
 static void collect_fn_hard_reg_usage (void);
+static tree get_call_fndecl (rtx);
 
 /* Initialize data in final at the beginning of a compilation.  */
 
@@ -4746,6 +4747,16 @@ make_pass_clean_state (gcc::context *ctxt)
   return new pass_clean_state (ctxt);
 }
 
+/* Return true if INSN is a call to the the current function.  */
+
+static bool
+self_recursive_call_p (rtx insn)
+{
+  tree fndecl = get_call_fndecl (insn);
+  return (fndecl == current_function_decl
+	  && decl_binds_to_current_def_p (fndecl));
+}
+
 /* Collect hard register usage for the current function.  */
 
 static void
@@ -4771,7 +4782,8 @@ collect_fn_hard_reg_usage (void)
       if (!NONDEBUG_INSN_P (insn))
 	continue;
 
-      if (CALL_P (insn))
+      if (CALL_P (insn)
+	  && !self_recursive_call_p (insn))
 	{
 	  if (!get_call_reg_set_usage (insn, &insn_used_regs,
 				       call_used_reg_set))

gcc/testsuite/gcc.target/i386/fuse-caller-save-rec.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fuse-caller-save -fomit-frame-pointer -fno-optimize-sibling-calls" } */
+/* { dg-additional-options "-mregparm=1" { target ia32 } } */
+
+/* Test -fuse-caller-save optimization on self-recursive function.  */
+
+static int __attribute__((noinline))
+bar (int x)
+{
+  if (x > 4)
+    return bar (x - 3);
+  return 0;
+}
+
+int __attribute__((noinline))
+foo (int y)
+{
+  return y + bar (y);
+}
+
+int
+main (void)
+{
+  return !(foo (5) == 13);
+}
+
+/* Verify that no registers where saved on stack.  */
+/* { dg-final { scan-assembler-not "\.cfi_offset"  } } */
+
+/* Verify that bar is self-recursive.  */
+/* { dg-final { scan-assembler-times "call\tbar" 2 } } */
+