sjlj eh flow patch

sjlj eh flow patch

[Richard Henderson]

The following patch generates more optimal basic block flows when
using sjlj by taking into account the fact that we know that longjmp
will go through a different path than the original call to setjmp.

It also gets rid of the stupid call to __dummy.  There is one backend
that needs to be fixed up because of this (MIPS); I'd been meaning to
do it but forgot.  If this patch is accepted for the post-1.00 release
I'll finish that bit.


r~


Mon Nov 10 18:48:02 1997  Richard Henderson  <rth@cygnus.com>

	* expr.c (expand_builtin_setjmp): Accept two new arguments for
	the labels to branch to on first and subsequent executions.  Don't
	play with __dummy.
	(expand_builtin) [BUILTIN_SETJMP]: Generate a label for use by setjmp.
	(expand_builtin) [BUILTIN_LONGJMP]: Don't play with __dummy.  Correct
	arguments to nonlocal_goto.
	* expr.h (expand_builtin_setjmp): Update prototype.
	* except.c (start_dynamic_handler): When using builtin_setjmp,
	generate correct flow information.
	
Index: except.c
===================================================================
RCS file: /cvs/cvsfiles/egcs/gcc/except.c,v
retrieving revision 1.10.2.1
diff -u -p -d -r1.10.2.1 except.c
--- except.c	1997/11/10 20:06:46	1.10.2.1
+++ except.c	1997/11/11 02:30:50
@@ -914,14 +914,17 @@ start_dynamic_handler ()
 #ifdef DONT_USE_BUILTIN_SETJMP
   x = emit_library_call_value (setjmp_libfunc, NULL_RTX, 1, SImode, 1,
 			       buf, Pmode);
+  /* If we come back here for a catch, transfer control to the handler.  */
+  jumpif_rtx (x, ehstack.top->entry->exception_handler_label);
 #else
-  x = expand_builtin_setjmp (buf, NULL_RTX);
+  {
+    /* A label to continue execution for the no exception case.  */
+    rtx noex = gen_label_rtx();
+    x = expand_builtin_setjmp (buf, NULL_RTX, noex,
+			       ehstack.top->entry->exception_handler_label);
+    emit_label (noex);
+  }
 #endif
-
-  /* If we come back here for a catch, transfer control to the
-     handler.  */
-
-  jumpif_rtx (x, ehstack.top->entry->exception_handler_label);
 
   /* We are committed to this, so update the handler chain.  */
 
Index: expr.c
===================================================================
RCS file: /cvs/cvsfiles/egcs/gcc/expr.c,v
retrieving revision 1.16
diff -u -p -d -r1.16 expr.c
--- expr.c	1997/11/02 05:15:13	1.16
+++ expr.c	1997/11/11 02:30:51
@@ -8072,20 +8072,16 @@ expand_builtin_return_addr (fndecl_code,
    them.  */
 
 rtx
-expand_builtin_setjmp (buf_addr, target)
+expand_builtin_setjmp (buf_addr, target, first_label, next_label)
      rtx buf_addr;
      rtx target;
+     rtx first_label, next_label;
 {
-  rtx lab1 = gen_label_rtx (), lab2 = gen_label_rtx ();
+  rtx lab1 = gen_label_rtx ();
   enum machine_mode sa_mode = Pmode, value_mode;
   rtx stack_save;
   int old_inhibit_defer_pop = inhibit_defer_pop;
-  int return_pops
-    =  RETURN_POPS_ARGS (get_identifier ("__dummy"),
-			 build_function_type (void_type_node, NULL_TREE),
-			 0);
   rtx next_arg_reg;
-  CUMULATIVE_ARGS args_so_far;
   rtx op0;
   int i;
 
@@ -8129,9 +8125,9 @@ expand_builtin_setjmp (buf_addr, target)
     emit_insn (gen_setjmp ());
 #endif
 
-  /* Set TARGET to zero and branch around the other case.  */
+  /* Set TARGET to zero and branch to the first-time-through label.  */
   emit_move_insn (target, const0_rtx);
-  emit_jump_insn (gen_jump (lab2));
+  emit_jump_insn (gen_jump (first_label));
   emit_barrier ();
   emit_label (lab1);
 
@@ -8151,12 +8147,7 @@ expand_builtin_setjmp (buf_addr, target)
 #endif
     emit_move_insn (virtual_stack_vars_rtx, hard_frame_pointer_rtx);
 
-  /* Do we need to do something like:
-     
-     current_function_has_nonlocal_label = 1;
-
-     here?  It seems like we might have to, or some subset of that
-     functionality, but I am unsure.  (mrs) */
+  current_function_has_nonlocal_label = 1;
 
 #if ARG_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
   if (fixed_regs[ARG_POINTER_REGNUM])
@@ -8189,39 +8180,12 @@ expand_builtin_setjmp (buf_addr, target)
   if (HAVE_nonlocal_goto_receiver)
     emit_insn (gen_nonlocal_goto_receiver ());
 #endif
-  /* The static chain pointer contains the address of dummy function.
-     We need to call it here to handle some PIC cases of restoring a
-     global pointer.  Then return 1.  */
-  op0 = copy_to_mode_reg (Pmode, static_chain_rtx);
-
-  /* We can't actually call emit_library_call here, so do everything
-     it does, which isn't much for a libfunc with no args.  */
-  op0 = memory_address (FUNCTION_MODE, op0);
-
-  INIT_CUMULATIVE_ARGS (args_so_far, NULL_TREE,
-			gen_rtx (SYMBOL_REF, Pmode, "__dummy"), 1);
-  next_arg_reg = FUNCTION_ARG (args_so_far, VOIDmode, void_type_node, 1);
-
-#ifndef ACCUMULATE_OUTGOING_ARGS
-#ifdef HAVE_call_pop
-  if (HAVE_call_pop)
-    emit_call_insn (gen_call_pop (gen_rtx (MEM, FUNCTION_MODE, op0),
-				  const0_rtx, next_arg_reg,
-				  GEN_INT (return_pops)));
-  else
-#endif
-#endif
-
-#ifdef HAVE_call
-    if (HAVE_call)
-      emit_call_insn (gen_call (gen_rtx (MEM, FUNCTION_MODE, op0),
-				const0_rtx, next_arg_reg, const0_rtx));
-    else
-#endif
-      abort ();
 
+  /* Set TARGET to one and branch to the next-time-through label.  */
   emit_move_insn (target, const1_rtx);
-  emit_label (lab2);
+  emit_jump_insn (gen_jump (next_label));
+  emit_barrier ();
+
   return target;
 }
 
@@ -9080,21 +9044,21 @@ expand_builtin (exp, target, subtarget, 
       {
 	rtx buf_addr = expand_expr (TREE_VALUE (arglist), subtarget,
 				    VOIDmode, 0);
-	return expand_builtin_setjmp (buf_addr, target);
+	rtx lab = gen_label_rtx ();
+	rtx ret = expand_builtin_setjmp (buf_addr, target, lab, lab);
+	emit_label (lab);
+	return ret;
       }
 
-      /* __builtin_longjmp is passed a pointer to an array of five words
-	 and a value, which is a dummy.  It's similar to the C library longjmp
-	 function but works with __builtin_setjmp above.  */
+      /* __builtin_longjmp is passed a pointer to an array of five words.
+	 It's similar to the C library longjmp function but works with
+	 __builtin_setjmp above.  */
     case BUILT_IN_LONGJMP:
       if (arglist == 0 || TREE_CHAIN (arglist) == 0
 	  || TREE_CODE (TREE_TYPE (TREE_VALUE (arglist))) != POINTER_TYPE)
 	break;
 
       {
-	tree dummy_id = get_identifier ("__dummy");
-	tree dummy_type = build_function_type (void_type_node, NULL_TREE);
-	tree dummy_decl = build_decl (FUNCTION_DECL, dummy_id, dummy_type); 
 #ifdef POINTERS_EXTEND_UNSIGNED
 	rtx buf_addr
 	  = force_reg (Pmode,
@@ -9123,35 +9087,24 @@ expand_builtin (exp, target, subtarget, 
 			     plus_constant (buf_addr,
 					    2 * GET_MODE_SIZE (Pmode)));
 
-	DECL_EXTERNAL (dummy_decl) = 1;
-	TREE_PUBLIC (dummy_decl) = 1;
-	make_decl_rtl (dummy_decl, NULL_PTR, 1);
-
 	/* Expand the second expression just for side-effects.  */
 	expand_expr (TREE_VALUE (TREE_CHAIN (arglist)),
 		     const0_rtx, VOIDmode, 0);
 
-	assemble_external (dummy_decl);
-
 	/* Pick up FP, label, and SP from the block and jump.  This code is
 	   from expand_goto in stmt.c; see there for detailed comments.  */
 #if HAVE_nonlocal_goto
 	if (HAVE_nonlocal_goto)
-	  emit_insn (gen_nonlocal_goto (fp, lab, stack,
-					XEXP (DECL_RTL (dummy_decl), 0)));
-      else
+	  emit_insn (gen_nonlocal_goto (fp, lab, stack, NULL_RTX));
+        else
 #endif
 	{
 	  lab = copy_to_reg (lab);
 	  emit_move_insn (hard_frame_pointer_rtx, fp);
 	  emit_stack_restore (SAVE_NONLOCAL, stack, NULL_RTX);
 
-	  /* Put in the static chain register the address of the dummy
-	     function.  */
-	  emit_move_insn (static_chain_rtx, XEXP (DECL_RTL (dummy_decl), 0));
 	  emit_insn (gen_rtx (USE, VOIDmode, hard_frame_pointer_rtx));
 	  emit_insn (gen_rtx (USE, VOIDmode, stack_pointer_rtx));
-	  emit_insn (gen_rtx (USE, VOIDmode, static_chain_rtx));
 	  emit_indirect_jump (lab);
 	}
 
Index: expr.h
===================================================================
RCS file: /cvs/cvsfiles/egcs/gcc/expr.h,v
retrieving revision 1.4
diff -u -p -d -r1.4 expr.h
--- expr.h	1997/08/29 15:02:03	1.4
+++ expr.h	1997/11/11 02:30:51
@@ -750,7 +750,7 @@ extern rtx store_expr PROTO((tree, rtx, 
    Useful after calling expand_expr with 1 as sum_ok.  */
 extern rtx force_operand PROTO((rtx, rtx));
 
-extern rtx expand_builtin_setjmp PROTO((rtx, rtx));
+extern rtx expand_builtin_setjmp PROTO((rtx, rtx, rtx, rtx));
 
 #ifdef TREE_CODE
 /* Generate code for computing expression EXP.

Re: sjlj eh flow patch

[Jeffrey A Law]

  In message < 19971110192354.31792@dot.cygnus.com >you write:
  > The following patch generates more optimal basic block flows when
  > using sjlj by taking into account the fact that we know that longjmp
  > will go through a different path than the original call to setjmp.
  > 
  > It also gets rid of the stupid call to __dummy.  There is one backend
  > that needs to be fixed up because of this (MIPS); I'd been meaning to
  > do it but forgot.  If this patch is accepted for the post-1.00 release
  > I'll finish that bit.
I think this should go in the mainline instead of the release branch.

jeff

Re: sjlj eh flow patch

[Jeffrey A Law]

  In message <19971110192354.31792@dot.cygnus.com>you write:
  > The following patch generates more optimal basic block flows when
  > using sjlj by taking into account the fact that we know that longjmp
  > will go through a different path than the original call to setjmp.
  > 
  > It also gets rid of the stupid call to __dummy.  There is one backend
  > that needs to be fixed up because of this (MIPS); I'd been meaning to
  > do it but forgot.  If this patch is accepted for the post-1.00 release
  > I'll finish that bit.
Conceptually it looks OK to me; though I recommend you run it by Jason
since he knows this code pretty well.  Also, it may need updating since
some of that code has likely changed over the last 6 weeks.

Jeff

Re: sjlj eh flow patch

[Jason Merrill]

>>>>> Jeffrey A Law <law@cygnus.com> writes:

>   In message <19971110192354.31792@dot.cygnus.com>you write:

>> The following patch generates more optimal basic block flows when
>> using sjlj by taking into account the fact that we know that longjmp
>> will go through a different path than the original call to setjmp.

> Conceptually it looks OK to me; though I recommend you run it by Jason
> since he knows this code pretty well.

Looks fine to me, too.  Looks like you don't need to mess with the flag at
all now, so you might as well tear out that code.

Jason