s390.c (override_options): Don't emit an error when -mstack-size is used without…

s390.c (override_options): Don't emit an error when -mstack-size is used without providing -mstack-guard.

2007-03-07  Andreas Krebbel  <krebbel1@de.ibm.com>

	* config/s390/s390.c (override_options): Don't emit an error when
	-mstack-size is used without providing -mstack-guard.
	(s390_emit_prologue): Choose stack_guard value automatically if not
	provided via command line.
	* doc/invoke.texi: Adjust description of -mstack-guard and -mstack-size.

From-SVN: r122655

gcc/ChangeLog

+2007-03-07  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	* config/s390/s390.c (override_options): Don't emit an error when
+	-mstack-size is used without providing -mstack-guard.
+	(s390_emit_prologue): Choose stack_guard value automatically if not
+	provided via command line.
+	* doc/invoke.texi: Adjust description of -mstack-guard and -mstack-size.
+
 2007-03-07  Richard Sandiford  <richard@codesourcery.com>
 
 	* config/i386/i386.c (output_set_got): Add a GOT initialization

gcc/config/s390/s390.c

@@ -1437,9 +1437,7 @@ override_options (void)
 
   if (s390_stack_size)
     {
-      if (!s390_stack_guard)
-	error ("-mstack-size implies use of -mstack-guard");
-      else if (s390_stack_guard >= s390_stack_size)
+      if (s390_stack_guard >= s390_stack_size)
 	error ("stack size must be greater than the stack guard value");
       else if (s390_stack_size > 1 << 16)
 	error ("stack size must not be greater than 64k");
@@ -7245,21 +7243,47 @@ s390_emit_prologue (void)
 
       if (s390_stack_size)
   	{
-	  HOST_WIDE_INT stack_check_mask = ((s390_stack_size - 1)
-					    & ~(s390_stack_guard - 1));
-	  rtx t = gen_rtx_AND (Pmode, stack_pointer_rtx,
-			       GEN_INT (stack_check_mask));
+	  HOST_WIDE_INT stack_guard;
 
-	  if (TARGET_64BIT)
-	    gen_cmpdi (t, const0_rtx);
+	  if (s390_stack_guard)
+	    stack_guard = s390_stack_guard;
 	  else
-	    gen_cmpsi (t, const0_rtx);
+	    {
+	      /* If no value for stack guard is provided the smallest power of 2
+		 larger than the current frame size is chosen.  */
+	      stack_guard = 1;
+	      while (stack_guard < cfun_frame_layout.frame_size)
+		stack_guard <<= 1;
+	    }
 
-	  emit_insn (gen_conditional_trap (gen_rtx_EQ (CCmode, 
-						       gen_rtx_REG (CCmode, 
-								    CC_REGNUM),
-						       const0_rtx),
-					   const0_rtx));
+	  if (cfun_frame_layout.frame_size >= s390_stack_size)
+	    {
+	      warning (0, "frame size of function %qs is "
+		       HOST_WIDE_INT_PRINT_DEC
+		       " bytes exceeding user provided stack limit of "
+		       HOST_WIDE_INT_PRINT_DEC " bytes.  "
+		       "An unconditional trap is added.",
+		       current_function_name(), cfun_frame_layout.frame_size,
+		       s390_stack_size);
+	      emit_insn (gen_trap ());
+	    }
+	  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));
+	    }
   	}
 
       if (s390_warn_framesize > 0 

gcc/doc/invoke.texi

@@ -12789,17 +12789,19 @@ sized arrays.  This is generally a bad idea with a limited stack size.
 @item -mstack-size=@var{stack-size}
 @opindex mstack-guard
 @opindex mstack-size
-These arguments always have to be used in conjunction.  If they are present the s390
-back end emits additional instructions in the function prologue which trigger a trap
-if the stack size is @var{stack-guard} bytes above the @var{stack-size}
-(remember that the stack on s390 grows downward).  These options are intended to
-be used to help debugging stack overflow problems.  The additionally emitted code
-causes only little overhead and hence can also be used in production like systems
-without greater performance degradation.  The given values have to be exact
-powers of 2 and @var{stack-size} has to be greater than @var{stack-guard} without
-exceeding 64k.
+If these options are provided the s390 back end emits additional instructions in
+the function prologue which trigger a trap if the stack size is @var{stack-guard}
+bytes above the @var{stack-size} (remember that the stack on s390 grows downward).
+If the @var{stack-guard} option is omitted the smallest power of 2 larger than
+the frame size of the compiled function is chosen.
+These options are intended to be used to help debugging stack overflow problems.
+The additionally emitted code causes only little overhead and hence can also be
+used in production like systems without greater performance degradation.  The given
+values have to be exact powers of 2 and @var{stack-size} has to be greater than
+@var{stack-guard} without exceeding 64k.
 In order to be efficient the extra code makes the assumption that the stack starts
 at an address aligned to the value given by @var{stack-size}.
+The @var{stack-guard} option can only be used in conjunction with @var{stack-size}.
 @end table
 
 @node Score Options