s390.c (s390_emit_prologue): Omit issuing a dynamic stack check if the mask would be zero.

2010-03-30  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>

	* config/s390/s390.c (s390_emit_prologue): Omit issuing a dynamic
	stack check if the mask would be zero.

2010-03-30  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>

	* gcc.target/s390/stackcheck1.c: New testcase.

From-SVN: r157825

gcc/ChangeLog

+2010-03-30  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
+
+	* config/s390/s390.c (s390_emit_prologue): Omit issuing a dynamic
+	stack check if the mask would be zero.
+
 2010-03-30  Seongbae Park <seongbae.park@gmail.com>
 	    Jack Howarth <howarth@bromo.med.uc.edu>
 

gcc/config/s390/s390.c

@@ -7802,18 +7802,37 @@ s390_emit_prologue (void)
 	    }
 	  else
 	    {
+	      /* stack_guard has to be smaller than s390_stack_size.
+		 Otherwise we would emit an AND with zero which would
+		 not match the test under mask pattern.  */
+	      if (stack_guard >= s390_stack_size)
+		{
+		  warning (0, "frame size of function %qs is "
+			   HOST_WIDE_INT_PRINT_DEC
+			   " bytes which is more than half the stack size. "
+			   "The dynamic check would not be reliable. "
+			   "No check emitted for this function.",
+			   current_function_name(),
+			   cfun_frame_layout.frame_size);
+		}
+	      else
+		{
 		  HOST_WIDE_INT stack_check_mask = ((s390_stack_size - 1)
 						    & ~(stack_guard - 1));
+
 		  rtx t = gen_rtx_AND (Pmode, stack_pointer_rtx,
 				       GEN_INT (stack_check_mask));
 		  if (TARGET_64BIT)
-	        emit_insn (gen_ctrapdi4 (gen_rtx_EQ (VOIDmode, t, const0_rtx),
+		    emit_insn (gen_ctrapdi4 (gen_rtx_EQ (VOIDmode,
+							 t, const0_rtx),
 					     t, const0_rtx, const0_rtx));
 		  else
-	        emit_insn (gen_ctrapsi4 (gen_rtx_EQ (VOIDmode, t, const0_rtx),
+		    emit_insn (gen_ctrapsi4 (gen_rtx_EQ (VOIDmode,
+							 t, const0_rtx),
 					     t, const0_rtx, const0_rtx));
 		}
 	    }
+  	}
 
       if (s390_warn_framesize > 0
 	  && cfun_frame_layout.frame_size >= s390_warn_framesize)

gcc/testsuite/ChangeLog

+2010-03-30  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
+
+	* gcc.target/s390/stackcheck1.c: New testcase.
+
 2010-03-29  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR libfortran/43265

gcc/testsuite/gcc.target/s390/stackcheck1.c

+/* The automatically chosen stack guard value caused an ICE in that
+   case.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -mstack-size=4096" } */
+
+extern void bar (char *);
+
+void
+foo ()
+{
+  char a[2500];
+  bar (a);
+}