File nvl938159.patch of Package gcc43

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.

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

Index: gcc/testsuite/gcc.target/s390/stackcheck1.c
===================================================================
--- gcc/testsuite/gcc.target/s390/stackcheck1.c	(revision 0)
+++ gcc/testsuite/gcc.target/s390/stackcheck1.c	(revision 157824)
@@ -0,0 +1,14 @@
+/* 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);
+}
Index: gcc/config/s390/s390.c
===================================================================
--- gcc/config/s390/s390.c	(revision 157823)
+++ gcc/config/s390/s390.c	(revision 157824)
@@ -7357,20 +7357,37 @@ s390_emit_prologue (void)
 	    }
 	  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)
-		gen_cmpdi (t, const0_rtx);
-	      else
-		gen_cmpsi (t, const0_rtx);
+ 	      /* 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)
+		    gen_cmpdi (t, const0_rtx);
+		  else
+		    gen_cmpsi (t, const0_rtx);
 
-	      emit_insn (gen_conditional_trap (gen_rtx_EQ (CCmode,
-							   gen_rtx_REG (CCmode,
-								     CC_REGNUM),
-							   const0_rtx),
-					       const0_rtx));
+		  emit_insn (gen_conditional_trap (
+                               gen_rtx_EQ (CCmode,
+					   gen_rtx_REG (CCmode,
+							CC_REGNUM),
+					   const0_rtx),
+			       const0_rtx));
+		}
 	    }
   	}