[PATCH] Fix ICE with COMPLEX_EXPR in fold_negate_expr (PR middle-end/79536)

[Marek Polacek <polacek at redhat dot com>]

For "(int) -x", which is a NOP_EXPR, negate_expr_p returns true, which means
that fold_negate_expr cannot return NULL_TREE.  But that's what happens here,
leading to a crash in fold_build2.  negate_expr_p has (as well as negate_expr)
STRIP_SIGN_NOPS, so the "(int) -x" becomes "-x", but fold_negate_expr doesn't
have any STRIP_SIGN_NOPS.  Richi suggested to add a wrapper for fold_negate_expr
that strips/restores such NOP_EXPRs, much like negate_expr, which is what this
patch does.

Bootstrapped/regtested on x86_64-linux, ok for trunk?  And 6 after a while?

2017-02-16  Marek Polacek  <polacek@redhat.com>

	PR middle-end/79536
	* fold-const.c (fold_negate_expr_1): Renamed from fold_negate_expr.
	(fold_negate_expr): New wrapper.

	* gcc.dg/torture/pr79536.c: New test.

diff --git gcc/fold-const.c gcc/fold-const.c
index a8bb8af..ad4770b 100644
--- gcc/fold-const.c
+++ gcc/fold-const.c
@@ -139,6 +139,7 @@ static tree fold_relational_const (enum tree_code, tree, tree, tree);
 static tree fold_convert_const (enum tree_code, tree, tree);
 static tree fold_view_convert_expr (tree, tree);
 static bool vec_cst_ctor_to_array (tree, tree *);
+static tree fold_negate_expr (location_t, tree);
 
 
 /* Return EXPR_LOCATION of T if it is not UNKNOWN_LOCATION.
@@ -522,7 +523,7 @@ negate_expr_p (tree t)
    returned.  */
 
 static tree
-fold_negate_expr (location_t loc, tree t)
+fold_negate_expr_1 (location_t loc, tree t)
 {
   tree type = TREE_TYPE (t);
   tree tem;
@@ -533,7 +534,7 @@ fold_negate_expr (location_t loc, tree t)
     case BIT_NOT_EXPR:
       if (INTEGRAL_TYPE_P (type))
         return fold_build2_loc (loc, PLUS_EXPR, type, TREE_OPERAND (t, 0),
-                            build_one_cst (type));
+				build_one_cst (type));
       break;
 
     case INTEGER_CST:
@@ -581,14 +582,14 @@ fold_negate_expr (location_t loc, tree t)
     case COMPLEX_EXPR:
       if (negate_expr_p (t))
 	return fold_build2_loc (loc, COMPLEX_EXPR, type,
-			    fold_negate_expr (loc, TREE_OPERAND (t, 0)),
-			    fold_negate_expr (loc, TREE_OPERAND (t, 1)));
+				fold_negate_expr (loc, TREE_OPERAND (t, 0)),
+				fold_negate_expr (loc, TREE_OPERAND (t, 1)));
       break;
 
     case CONJ_EXPR:
       if (negate_expr_p (t))
 	return fold_build1_loc (loc, CONJ_EXPR, type,
-			    fold_negate_expr (loc, TREE_OPERAND (t, 0)));
+				fold_negate_expr (loc, TREE_OPERAND (t, 0)));
       break;
 
     case NEGATE_EXPR:
@@ -605,7 +606,7 @@ fold_negate_expr (location_t loc, tree t)
 	    {
 	      tem = negate_expr (TREE_OPERAND (t, 1));
 	      return fold_build2_loc (loc, MINUS_EXPR, type,
-				  tem, TREE_OPERAND (t, 0));
+				      tem, TREE_OPERAND (t, 0));
 	    }
 
 	  /* -(A + B) -> (-A) - B.  */
@@ -613,7 +614,7 @@ fold_negate_expr (location_t loc, tree t)
 	    {
 	      tem = negate_expr (TREE_OPERAND (t, 0));
 	      return fold_build2_loc (loc, MINUS_EXPR, type,
-				  tem, TREE_OPERAND (t, 1));
+				      tem, TREE_OPERAND (t, 1));
 	    }
 	}
       break;
@@ -623,7 +624,7 @@ fold_negate_expr (location_t loc, tree t)
       if (!HONOR_SIGN_DEPENDENT_ROUNDING (element_mode (type))
 	  && !HONOR_SIGNED_ZEROS (element_mode (type)))
 	return fold_build2_loc (loc, MINUS_EXPR, type,
-			    TREE_OPERAND (t, 1), TREE_OPERAND (t, 0));
+				TREE_OPERAND (t, 1), TREE_OPERAND (t, 0));
       break;
 
     case MULT_EXPR:
@@ -638,11 +639,11 @@ fold_negate_expr (location_t loc, tree t)
 	  tem = TREE_OPERAND (t, 1);
 	  if (negate_expr_p (tem))
 	    return fold_build2_loc (loc, TREE_CODE (t), type,
-				TREE_OPERAND (t, 0), negate_expr (tem));
+				    TREE_OPERAND (t, 0), negate_expr (tem));
 	  tem = TREE_OPERAND (t, 0);
 	  if (negate_expr_p (tem))
 	    return fold_build2_loc (loc, TREE_CODE (t), type,
-				negate_expr (tem), TREE_OPERAND (t, 1));
+				    negate_expr (tem), TREE_OPERAND (t, 1));
 	}
       break;
 
@@ -715,6 +716,19 @@ fold_negate_expr (location_t loc, tree t)
   return NULL_TREE;
 }
 
+/* A wrapper for fold_negate_expr_1.  */
+
+static tree
+fold_negate_expr (location_t loc, tree t)
+{
+  tree type = TREE_TYPE (t);
+  STRIP_SIGN_NOPS (t);
+  tree tem = fold_negate_expr_1 (loc, t);
+  if (tem == NULL_TREE)
+    return NULL_TREE;
+  return fold_convert_loc (loc, type, tem);
+}
+
 /* Like fold_negate_expr, but return a NEGATE_EXPR tree, if T can not be
    negated in a simpler way.  Also allow for T to be NULL_TREE, in which case
    return NULL_TREE. */
diff --git gcc/testsuite/gcc.dg/torture/pr79536.c gcc/testsuite/gcc.dg/torture/pr79536.c
index e69de29..6f05ca7 100644
--- gcc/testsuite/gcc.dg/torture/pr79536.c
+++ gcc/testsuite/gcc.dg/torture/pr79536.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+
+typedef int A;
+int
+fn1 (A x, A y)
+{
+  if ((x + (x - y) * 1i) != -(-x + (y - x) * 1i))
+    return 1;
+  return 0;
+}

	Marek