strub: Only unbias stack point for SPARC_STACK_BOUNDARY_HACK [PR113100]

As PR113100 shows, the unbiasing introduced by r14-6737 can
cause the scrubbing to overrun and screw some critical data
on stack like saved toc base consequently cause segfault.

By checking PR112917, IMHO we should keep this unbiasing
guarded under SPARC_STACK_BOUNDARY_HACK (TARGET_ARCH64 &&
TARGET_STACK_BIAS), similar to some existing code special
treating SPARC stack bias.

	PR middle-end/113100

gcc/ChangeLog:

	* builtins.cc (expand_builtin_stack_address): Guard stack point
	adjustment with SPARC_STACK_BOUNDARY_HACK.

gcc/builtins.cc

@@ -5450,6 +5450,7 @@ expand_builtin_stack_address ()
   rtx ret = convert_to_mode (ptr_mode, copy_to_reg (stack_pointer_rtx),
 			     STACK_UNSIGNED);
 
+#ifdef SPARC_STACK_BOUNDARY_HACK
   /* Unbias the stack pointer, bringing it to the boundary between the
      stack area claimed by the active function calling this builtin,
      and stack ranges that could get clobbered if it called another
@@ -5476,7 +5477,9 @@ expand_builtin_stack_address ()
      (caller) function's active area as well, whereas those pushed or
      allocated temporarily for a call are regarded as part of the
      callee's stack range, rather than the caller's.  */
-  ret = plus_constant (ptr_mode, ret, STACK_POINTER_OFFSET);
+  if (SPARC_STACK_BOUNDARY_HACK)
+    ret = plus_constant (ptr_mode, ret, STACK_POINTER_OFFSET);
+#endif
 
   return force_reg (ptr_mode, ret);
 }