Make the AAPCS64 function return tests more robust.

gcc/testsuite

	* gcc.target/aarch64/aapcs64/abitest-2.h (saved_return_address): New
	global variable.
	(FUNC_VAL_CHECK): Update to call myfunc via the 'ret' instruction,
	instead of calling sequentially in the C code.
	* gcc.target/aarch64/aapcs64/abitest.S (LABEL_TEST_FUNC_RETURN): Store
	saved_return_address to the stack frame where LR register was stored.
	(saved_return_address): Declare weak.

From-SVN: r211954

gcc/testsuite/ChangeLog

+2014-06-24  Yufeng Zhang  <yufeng.zhang@arm.com>
+
+	* gcc.target/aarch64/aapcs64/abitest-2.h (saved_return_address): New
+	global variable.
+	(FUNC_VAL_CHECK): Update to call myfunc via the 'ret' instruction,
+	instead of calling sequentially in the C code.
+	* gcc.target/aarch64/aapcs64/abitest.S (LABEL_TEST_FUNC_RETURN): Store
+	saved_return_address to the stack frame where LR register was stored.
+	(saved_return_address): Declare weak.
+
 2014-06-24  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/33972

gcc/testsuite/gcc.target/aarch64/aapcs64/abitest-2.h

@@ -5,6 +5,7 @@
 #include "validate_memory.h"
 
 void (*testfunc_ptr)(char* stack);
+unsigned long long saved_return_address;
 
 /* Helper macros to generate function name.  Example of the function name:
    func_return_val_1.  */
@@ -71,6 +72,17 @@ __attribute__ ((noinline)) type FUNC_NAME (id) (int i, double d, type t)  \
 				  optimized away.  Using i and d prevents \
 				  warnings about unused parameters.	  \
 			       */					  \
+    /* We save and set up the LR register in a way that essentially	  \
+       inserts myfunc () between the return of this function and the	  \
+       continuing execution of its caller.  By doing this, myfunc ()	  \
+       can save and check the exact content of the registers that are	  \
+       used for the function return value.				  \
+       The previous approach of sequentially calling myfunc right after	  \
+       this function does not guarantee myfunc see the exact register	  \
+       content, as compiler may emit code in between the two calls,	  \
+       especially during the -O0 codegen.  */				  \
+    asm volatile ("mov %0, x30" : "=r" (saved_return_address));		  \
+    asm volatile ("mov x30, %0" : : "r" ((unsigned long long) myfunc));   \
     return t;								  \
   }
 #include TESTFILE
@@ -84,7 +96,8 @@ __attribute__ ((noinline)) type FUNC_NAME (id) (int i, double d, type t)  \
   {									\
     testfunc_ptr = TEST_FUNC_NAME(id);					\
     FUNC_NAME(id) (0, 0.0, var);					\
-    myfunc ();								\
+    /* The above function implicitly calls myfunc () on its return,	\
+       and the execution resumes from here after myfunc () finishes.  */\
   }
 
 int main()

gcc/testsuite/gcc.target/aarch64/aapcs64/abitest.S

@@ -50,6 +50,10 @@ LABEL_TEST_FUNC_RETURN:
       add	x9, x9, :lo12:testfunc_ptr
       ldr	x9, [x9, #0]
       blr	x9				// function return value test
+      adrp	x9, saved_return_address
+      add	x9, x9, :lo12:saved_return_address
+      ldr	x9, [x9, #0]
+      str	x9, [sp, #8]			// Update the copy of LR reg saved on stack
 LABEL_RET:
       ldp	x0, x30, [sp]
       mov	sp, x0
@@ -57,3 +61,4 @@ LABEL_RET:
 
 .weak	testfunc
 .weak	testfunc_ptr
+.weak	saved_return_address