expr.c (expand_expr): Never modify exp in place.

	* expr.c (expand_expr) <case COND_EXPR>: Never modify exp in place.

	* gcc.c-torture/execute/20021204-1.c: New test.

From-SVN: r59881

1 files changed, 7 insertions, 15 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index 8851343..144bc00 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -8618,6 +8618,7 @@ expand_expr (exp, target, tmode, modifier)
 	    && TREE_CODE_CLASS (TREE_CODE (TREE_OPERAND (exp, 0))) == '<')
 	  {
 	    rtx result;
+	    tree cond;
 	    optab boptab = (TREE_CODE (binary_op) == PLUS_EXPR
 			    ? (TYPE_TRAP_SIGNED (TREE_TYPE (binary_op))
 			       ? addv_optab : add_optab)
@@ -8627,20 +8628,14 @@ expand_expr (exp, target, tmode, modifier)
 			    : TREE_CODE (binary_op) == BIT_IOR_EXPR ? ior_optab
 			    : xor_optab);
 
-	    /* If we had X ? A : A + 1, do this as A + (X == 0).
-
-	       We have to invert the truth value here and then put it
-	       back later if do_store_flag fails.  We cannot simply copy
-	       TREE_OPERAND (exp, 0) to another variable and modify that
-	       because invert_truthvalue can modify the tree pointed to
-	       by its argument.  */
+	    /* If we had X ? A : A + 1, do this as A + (X == 0).  */
 	    if (singleton == TREE_OPERAND (exp, 1))
-	      TREE_OPERAND (exp, 0)
-		= invert_truthvalue (TREE_OPERAND (exp, 0));
+	      cond = invert_truthvalue (TREE_OPERAND (exp, 0));
+	    else
+	      cond = TREE_OPERAND (exp, 0);
 
-	    result = do_store_flag (TREE_OPERAND (exp, 0),
-				    (safe_from_p (temp, singleton, 1)
-				     ? temp : NULL_RTX),
+	    result = do_store_flag (cond, (safe_from_p (temp, singleton, 1)
+					   ? temp : NULL_RTX),
 				    mode, BRANCH_COST <= 1);
 
 	    if (result != 0 && ! integer_onep (TREE_OPERAND (binary_op, 1)))
@@ -8658,9 +8653,6 @@ expand_expr (exp, target, tmode, modifier)
 		return expand_binop (mode, boptab, op1, result, temp,
 				     unsignedp, OPTAB_LIB_WIDEN);
 	      }
-	    else if (singleton == TREE_OPERAND (exp, 1))
-	      TREE_OPERAND (exp, 0)
-		= invert_truthvalue (TREE_OPERAND (exp, 0));
 	  }
 
 	do_pending_stack_adjust ();