re PR target/51643 (Incorrect code produced for tail-call of weak function with -O2/-O3 option)

	PR target/51643
	* arm.c (arm_function_ok_for_sibcall): Don't try to tailcall a
	weak function on bare-metal EABI targets.

	* gcc.target/arm/sibcall-2.c: New test.

From-SVN: r182621

gcc/ChangeLog

+2011-12-21  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR target/51643
+	* arm.c (arm_function_ok_for_sibcall): Don't try to tailcall a
+	weak function on bare-metal EABI targets.
+
 2011-12-21  Jonathan Wakely  <jwakely.gcc@gmail.com>
 	    Jim Avera  <james_avera@yahoo.com>
 

gcc/config/arm/arm.c

@@ -5250,6 +5250,14 @@ arm_function_ok_for_sibcall (tree decl, tree exp)
   if (IS_STACKALIGN (func_type))
     return false;
 
+  /* The AAPCS says that, on bare-metal, calls to unresolved weak
+     references should become a NOP.  Don't convert such calls into
+     sibling calls.  */
+  if (TARGET_AAPCS_BASED
+      && arm_abi == ARM_ABI_AAPCS
+      && lookup_attribute ("weak", DECL_ATTRIBUTES (decl)))
+    return false;
+
   /* Everything else is ok.  */
   return true;
 }

gcc/testsuite/ChangeLog

+2011-12-21  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR target/51643
+	* gcc.target/arm/sibcall-2.c: New test.
+
 2011-12-22  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR testsuite/51645

gcc/testsuite/gcc.target/arm/sibcall-2.c

+/* { dg-require-effective-target arm_eabi } */
+/* { dg-do compile } */
+/* { dg-options "-O2 -mabi=aapcs" } */
+
+
+extern void __attribute__((weak)) wfunc(void);
+void main(void)
+{
+  wfunc();  /* Must not tail-call.  */
+}
+
+/* { dg-final { scan-assembler-not "b\[\\t \]+wfunc" } } */