re PR tree-optimization/42154 (Wrong code from (early) SRA)

2009-11-24  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/42154
	* tree-sra.c (struct access): Added comments.
	(sra_modify_expr): Build references to the old aggregate with
	build_ref_for_offset instead of reusing access->expr.
	(load_assign_lhs_subreplacements): Likewise.

	* testsuite/gcc.c-torture/execute/pr42154.c: New test.

From-SVN: r154493

gcc/ChangeLog

@@ -1,3 +1,11 @@
+2009-11-24  Martin Jambor  <mjambor@suse.cz>
+
+	PR tree-optimization/42154
+	* tree-sra.c (struct access): Added comments.
+	(sra_modify_expr): Build references to the old aggregate with
+	build_ref_for_offset instead of reusing access->expr.
+	(load_assign_lhs_subreplacements): Likewise.
+
 2009-11-24  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.md (add<mode>3_carry): Change insn pattern

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2009-11-24  Martin Jambor  <mjambor@suse.cz>
+
+	PR tree-optimization/42154
+	* gcc.c-torture/execute/pr42154.c: New test.
+
 2009-11-24  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/42045

gcc/testsuite/gcc.c-torture/execute/pr42154.c

@@ -0,0 +1,18 @@
+struct A { char x[1]; };
+extern void abort (void);
+void __attribute__((noinline,noclone))
+foo (struct A a)
+{
+  if (a.x[0] != 'a')
+    abort ();
+}
+int main ()
+{
+  struct A a;
+  int i;
+  for (i = 0; i < 1; ++i)
+    a.x[i] = 'a';
+  foo (a);
+  return 0;
+}
+

gcc/tree-sra.c

@@ -125,7 +125,9 @@ struct access
   HOST_WIDE_INT size;
   tree base;
 
-  /* Expression.  */
+  /* Expression.  It is context dependent so do not use it to create new
+     expressions to access the original aggregate.  See PR 42154 for a
+     testcase.  */
   tree expr;
   /* Type.  */
   tree type;
@@ -2113,10 +2115,17 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi, bool write,
 	 gcc.c-torture/compile/20011217-1.c.  */
       if (!is_gimple_reg_type (type))
 	{
-	  gimple stmt;
+	  tree ref = access->base;
+	  bool ok;
+
+	  ok = build_ref_for_offset (&ref, TREE_TYPE (ref),
+				     access->offset, access->type, false);
+	  gcc_assert (ok);
+
 	  if (write)
 	    {
-	      tree ref = unshare_expr (access->expr);
+	      gimple stmt;
+
 	      if (access->grp_partial_lhs)
 		ref = force_gimple_operand_gsi (gsi, ref, true, NULL_TREE,
 						 false, GSI_NEW_STMT);
@@ -2125,10 +2134,12 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi, bool write,
 	    }
 	  else
 	    {
+	      gimple stmt;
+
 	      if (access->grp_partial_lhs)
 		repl = force_gimple_operand_gsi (gsi, repl, true, NULL_TREE,
 						 true, GSI_SAME_STMT);
-	      stmt = gimple_build_assign (unshare_expr (access->expr), repl);
+	      stmt = gimple_build_assign (ref, repl);
 	      gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
 	    }
 	}
@@ -2227,8 +2238,6 @@ load_assign_lhs_subreplacements (struct access *lacc, struct access *top_racc,
 	    }
 	  else
 	    {
-	      bool repl_found;
-
 	      /* No suitable access on the right hand side, need to load from
 		 the aggregate.  See if we have to update it first... */
 	      if (*refreshed == SRA_UDH_NONE)
@@ -2236,9 +2245,19 @@ load_assign_lhs_subreplacements (struct access *lacc, struct access *top_racc,
 								  lhs, old_gsi);
 
 	      if (*refreshed == SRA_UDH_LEFT)
-		rhs = unshare_expr (lacc->expr);
+		{
+		  bool repl_found;
+
+		  rhs = lacc->base;
+		  repl_found = build_ref_for_offset (&rhs, TREE_TYPE (rhs),
+						     lacc->offset, lacc->type,
+						     false);
+		  gcc_assert (repl_found);
+		}
 	      else
 		{
+		  bool repl_found;
+
 		  rhs = top_racc->base;
 		  repl_found = build_ref_for_offset (&rhs,
 						     TREE_TYPE (top_racc->base),