rs6000: mark clobber for registers changed by untpyed_call

As PR93047 said, __builtin_apply/__builtin_return does not work well with
-frename-registers.  This is caused by return register(e.g. r3) is used to
rename another register, before return register is stored to stack.
This patch fix this issue by emitting clobber for those egisters which
maybe changed by untyped call.

gcc/
2020-02-17  Jiufu Guo  <guojiufu@linux.ibm.com>

	PR target/93047
	* config/rs6000/rs6000.md (untyped_call): Add emit_clobber.

gcc/testsuite
2020-02-17  Jiufu Guo  <guojiufu@linux.ibm.com>

	PR target/93047
	* gcc.dg/torture/stackalign/builtin-return-2.c: New test case.

gcc/ChangeLog

+2020-02-17  Jiufu Guo  <guojiufu@linux.ibm.com>
+
+	PR target/93047
+	* config/rs6000/rs6000.md (untyped_call): Add emit_clobber.
+
 2020-02-16  Uroš Bizjak  <ubizjak@gmail.com>
 
 	PR target/93743

gcc/config/rs6000/rs6000.md

@@ -10870,6 +10870,10 @@
 
   emit_call_insn (gen_call (operands[0], const0_rtx, const0_rtx));
 
+  for (int i = 0; i < XVECLEN (operands[2], 0); i++)
+    emit_clobber (SET_SRC (XVECEXP (operands[2], 0, i)));
+  emit_insn (gen_blockage ());
+
   for (i = 0; i < XVECLEN (operands[2], 0); i++)
     {
       rtx set = XVECEXP (operands[2], 0, i);

gcc/testsuite/ChangeLog

+2020-02-17  Jiufu Guo  <guojiufu@linux.ibm.com>
+
+	PR target/93047
+	* gcc.dg/torture/stackalign/builtin-return-2.c: New test case.
+
 2020-02-16  Uroš Bizjak  <ubizjak@gmail.com>
 
 	PR target/93743

gcc/testsuite/gcc.dg/torture/stackalign/builtin-return-2.c

+/* PR target/93047 */
+/* Originator: Andrew Church <gcczilla@achurch.org> */
+/* { dg-do run } */
+/* { dg-additional-options "-O3 -frename-registers" } */
+/* { dg-require-effective-target untyped_assembly } */
+
+#ifdef __MMIX__
+/* No parameters on stack for bar.  */
+#define STACK_ARGUMENTS_SIZE 0
+#else
+#define STACK_ARGUMENTS_SIZE 64
+#endif
+
+extern void abort(void);
+
+int foo(int n)
+{
+  return n+1;
+}
+
+int bar(int n)
+{
+  __builtin_return(__builtin_apply((void (*)(void))foo, __builtin_apply_args(),
+				   STACK_ARGUMENTS_SIZE));
+}
+
+int main(void)
+{
+  /* Allocate 64 bytes on the stack to make sure that __builtin_apply
+     can read at least 64 bytes above the return address.  */
+  char dummy[64];
+
+  __asm__ ("" : : "" (dummy));
+
+  if (bar(1) != 2)
+    abort();
+
+  return 0;
+}
+