[1/N] Preserve loop structures from tree loop to RTL loop optimizers

Index: gcc/optabs.h
===================================================================
--- gcc/optabs.h	(revision 184918)
+++ gcc/optabs.h	(working copy)
@@ -1103,6 +1103,25 @@  set_direct_optab_handler (direct_optab o
   op->handlers[(int) mode].insn_code = (int) code - (int) CODE_FOR_nothing;
 }
 
+/* Return true if UNOPTAB is for a trapping-on-overflow operation.  */
+
+static inline bool
+trapv_unoptab_p (optab unoptab)
+{
+  return (unoptab == negv_optab
+	  || unoptab == absv_optab); 
+}
+
+/* Return true if BINOPTAB is for a trapping-on-overflow operation.  */
+
+static inline bool
+trapv_binoptab_p (optab binoptab)
+{
+  return (binoptab == addv_optab
+	  || binoptab == subv_optab
+	  || binoptab == smulv_optab);
+}
+
 extern rtx optab_libfunc (optab optab, enum machine_mode mode);
 extern rtx convert_optab_libfunc (convert_optab optab, enum machine_mode mode1,
 			          enum machine_mode mode2);
Index: gcc/optabs.c
===================================================================
--- gcc/optabs.c	(revision 184918)
+++ gcc/optabs.c	(working copy)
@@ -60,6 +60,7 @@  optab code_to_optab[NUM_RTX_CODE + 1];
 static void prepare_float_lib_cmp (rtx, rtx, enum rtx_code, rtx *,
 				   enum machine_mode *);
 static rtx expand_unop_direct (enum machine_mode, optab, rtx, rtx, int);
+static void emit_libcall_block_1 (rtx, rtx, rtx, rtx, bool);
 
 /* Debug facility for use in GDB.  */
 void debug_optab_libfuncs (void);
@@ -2115,8 +2116,9 @@  expand_binop (enum machine_mode mode, op
       end_sequence ();
 
       target = gen_reg_rtx (mode);
-      emit_libcall_block (insns, target, value,
-			  gen_rtx_fmt_ee (binoptab->code, mode, op0, op1));
+      emit_libcall_block_1 (insns, target, value,
+			    gen_rtx_fmt_ee (binoptab->code, mode, op0, op1),
+			    trapv_binoptab_p (binoptab));
 
       return target;
     }
@@ -3197,7 +3199,8 @@  expand_unop (enum machine_mode mode, opt
 	eq_value = simplify_gen_unary (TRUNCATE, outmode, eq_value, mode);
       else if (GET_MODE_SIZE (outmode) > GET_MODE_SIZE (mode))
 	eq_value = simplify_gen_unary (ZERO_EXTEND, outmode, eq_value, mode);
-      emit_libcall_block (insns, target, value, eq_value);
+      emit_libcall_block_1 (insns, target, value, eq_value,
+			    trapv_unoptab_p (unoptab));
 
       return target;
     }
@@ -3775,8 +3778,9 @@  no_conflict_move_test (rtx dest, const_r
    an insn to move RESULT to TARGET.  This last insn will have a REQ_EQUAL
    note with an operand of EQUIV.  */
 
-void
-emit_libcall_block (rtx insns, rtx target, rtx result, rtx equiv)
+static void
+emit_libcall_block_1 (rtx insns, rtx target, rtx result, rtx equiv,
+		      bool equiv_may_trap)
 {
   rtx final_dest = target;
   rtx next, last, insn;
@@ -3789,7 +3793,8 @@  emit_libcall_block (rtx insns, rtx targe
   /* If we're using non-call exceptions, a libcall corresponding to an
      operation that may trap may also trap.  */
   /* ??? See the comment in front of make_reg_eh_region_note.  */
-  if (cfun->can_throw_non_call_exceptions && may_trap_p (equiv))
+  if (cfun->can_throw_non_call_exceptions
+      && (equiv_may_trap || may_trap_p (equiv)))
     {
       for (insn = insns; insn; insn = NEXT_INSN (insn))
 	if (CALL_P (insn))
@@ -3870,6 +3875,12 @@  emit_libcall_block (rtx insns, rtx targe
   if (final_dest != target)
     emit_move_insn (final_dest, target);
 }
+
+void
+emit_libcall_block (rtx insns, rtx target, rtx result, rtx equiv)
+{
+  emit_libcall_block_1 (insns, target, result, equiv, false);
+}
 
 /* Nonzero if we can perform a comparison of mode MODE straightforwardly.
    PURPOSE describes how this comparison will be used.  CODE is the rtx