From 8cadeff16d7cde70baac185d8516d7f8f2a7ae36 Mon Sep 17 00:00:00 2001
From: Roger Sayle <roger@eyesopen.com>
Date: Wed, 15 Jan 2003 17:44:37 +0000
Subject: [PATCH] c-semantics.c (genrtl_while_stmt): Improve initial RTL
 generation when loop condition is known true, i.e.

	* c-semantics.c (genrtl_while_stmt):  Improve initial RTL generation
	when loop condition is known true, i.e.  "while (1) { ... }".
	(genrtl_for_stmt): Similarly for "for" statements.

From-SVN: r61338
---
 gcc/ChangeLog     |  6 ++++++
 gcc/c-semantics.c | 30 ++++++++++++++++++------------
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 503ad571ad7..06387e8aaac 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2003-01-15  Roger Sayle  <roger@eyesopen.com>
+
+	* c-semantics.c (genrtl_while_stmt):  Improve initial RTL generation
+	when loop condition is known true, i.e.  "while (1) { ... }".
+	(genrtl_for_stmt): Similarly for "for" statements.
+
 2003-01-15  Roger Sayle  <roger@eyesopen.com>
 
 	* real.c (real_sqrt): Return a bool result indicating whether
diff --git a/gcc/c-semantics.c b/gcc/c-semantics.c
index 769c1165d4a..e19e73e47e8 100644
--- a/gcc/c-semantics.c
+++ b/gcc/c-semantics.c
@@ -1,7 +1,7 @@
 /* This file contains the definitions and documentation for the common
    tree codes used in the GNU C and C++ compilers (see c-common.def
    for the standard codes).  
-   Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
+   Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
    Written by Benjamin Chelf (chelf@codesourcery.com).
 
 This file is part of GCC.
@@ -424,16 +424,20 @@ void
 genrtl_while_stmt (t)
      tree t;
 {
-  tree cond;
+  tree cond = WHILE_COND (t);
+
   emit_nop ();
   emit_line_note (input_filename, lineno);
   expand_start_loop (1); 
   genrtl_do_pushlevel ();
 
-  cond = expand_cond (WHILE_COND (t));
-  emit_line_note (input_filename, lineno);
-  expand_exit_loop_top_cond (0, cond);
-  genrtl_do_pushlevel ();
+  if (cond && !integer_nonzerop (cond))
+    {
+      cond = expand_cond (cond);
+      emit_line_note (input_filename, lineno);
+      expand_exit_loop_top_cond (0, cond);
+      genrtl_do_pushlevel ();
+    }
   
   expand_stmt (WHILE_BODY (t));
 
@@ -522,7 +526,7 @@ void
 genrtl_for_stmt (t)
      tree t;
 {
-  tree cond;
+  tree cond = FOR_COND (t);
   const char *saved_filename;
   int saved_lineno;
 
@@ -539,7 +543,6 @@ genrtl_for_stmt (t)
   else
     expand_start_loop (1);
   genrtl_do_pushlevel ();
-  cond = expand_cond (FOR_COND (t));
 
   /* Save the filename and line number so that we expand the FOR_EXPR
      we can reset them back to the saved values.  */
@@ -547,12 +550,15 @@ genrtl_for_stmt (t)
   saved_lineno = lineno;
 
   /* Expand the condition.  */
-  emit_line_note (input_filename, lineno);
-  if (cond)
-    expand_exit_loop_top_cond (0, cond);
+  if (cond && !integer_nonzerop (cond))
+    {
+      cond = expand_cond (cond);
+      emit_line_note (input_filename, lineno);
+      expand_exit_loop_top_cond (0, cond);
+      genrtl_do_pushlevel ();
+    }
 
   /* Expand the body.  */
-  genrtl_do_pushlevel ();
   expand_stmt (FOR_BODY (t));
 
   /* Expand the increment expression.  */