See http://gcc.gnu.org/PR21173
This is a fix for a last minute brown-bag bug with gcc-4.0.0

 ------- Additional Comment #24 From CVS Commits 2005-04-25 14:03 [reply] ------- 
Subject: Bug 21173

CVSROOT:        /cvs/gcc
Module name:    gcc
Branch:         gcc-4_0-branch
Changes by:     dberlin@gcc.gnu.org     2005-04-25 14:02:38

Modified files:
        gcc            : ChangeLog tree-ssa-pre.c 

Log message:
        2005-04-25  Daniel Berlin  <dberlin@dberlin.org>
        
        Fix PR tree-optimization/21173
        
        * tree-ssa-pre.c (create_expression_by_pieces): Call unshare_expr
        on things we pass to force_gimple_operand.  Don't try to special
        case min_invariants.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=2.7592.2.192&r2=2.7592.2.193
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-ssa-pre.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=2.65.4.2&r2=2.65.4.3

===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-pre.c,v
retrieving revision 2.65.4.2
retrieving revision 2.65.4.3
diff -u -r2.65.4.2 -r2.65.4.3
--- gcc/gcc/tree-ssa-pre.c	2005/04/17 23:40:31	2.65.4.2
+++ gcc/gcc/tree-ssa-pre.c	2005/04/25 14:02:31	2.65.4.3
@@ -1330,7 +1330,8 @@
 	
 	folded = fold (build (TREE_CODE (expr), TREE_TYPE (expr), 
 			      genop1, genop2));
-	newexpr = force_gimple_operand (folded, &forced_stmts, false, NULL);
+	newexpr = force_gimple_operand (unshare_expr (folded), 
+					&forced_stmts, false, NULL);
 	if (forced_stmts)
 	  {
 	    tsi = tsi_start (forced_stmts);
@@ -1372,14 +1373,8 @@
 	add_referenced_tmp_var (temp);
 	folded = fold (build (TREE_CODE (expr), TREE_TYPE (expr), 
 			      genop1));
-	/* If the generated operand  is already GIMPLE min_invariant
-	   just use it instead of calling force_gimple_operand on it,
-	   since that may make it not invariant by copying it into an
-	   assignment.  */
-	if (!is_gimple_min_invariant (genop1))
-	  newexpr = force_gimple_operand (folded, &forced_stmts, false, NULL);
-	else
-	  newexpr = genop1;
+	newexpr = force_gimple_operand (unshare_expr (folded), 
+					&forced_stmts, false, NULL);
 	if (forced_stmts)
 	  {
 	    tsi = tsi_start (forced_stmts);

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13:16:54 (1.24 MB/s) - `-' saved [1303]