Use tree_vector_builder::new_unary_operation for folding

This patch makes fold-const.c operate directly on the VECTOR_CST
encoding when folding an operation that has a single VECTOR_CST input.

2017-12-07  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* fold-const.c (fold_negate_expr_1): Use tree_vector_builder and
	new_unary_operation, operating only on the encoded elements.
	(const_unop): Likewise.
	(exact_inverse): Likewise.
	(distributes_over_addition_p): New function.
	(const_binop): Use tree_vector_builder and new_unary_operation
	for combinations of VECTOR_CST and INTEGER_CST.  Operate only
	on the encoded elements unless the encoding is strided and the
	operation does not distribute over addition.
	(fold_convert_const):  Use tree_vector_builder and
	new_unary_operation.  Operate only on the encoded elements
	for truncating integer conversions, or for non-stepped encodings.

From-SVN: r255476

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f0fca0eba15ca48d30398ac25ff6b353c38311a9..c541ad72c08117ddc921244e807116313cddeb2a 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,18 @@
+2017-12-07  Richard Sandiford  <richard.sandiford@linaro.org>
+
+       * fold-const.c (fold_negate_expr_1): Use tree_vector_builder and
+       new_unary_operation, operating only on the encoded elements.
+       (const_unop): Likewise.
+       (exact_inverse): Likewise.
+       (distributes_over_addition_p): New function.
+       (const_binop): Use tree_vector_builder and new_unary_operation
+       for combinations of VECTOR_CST and INTEGER_CST.  Operate only
+       on the encoded elements unless the encoding is strided and the
+       operation does not distribute over addition.
+       (fold_convert_const):  Use tree_vector_builder and
+       new_unary_operation.  Operate only on the encoded elements
+       for truncating integer conversions, or for non-stepped encodings.
+
 2017-12-07  Richard Sandiford  <richard.sandiford@linaro.org>
 
        * config/sparc/sparc.c: Include tree-vector-builder.h.

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 87f07bf16c0281e6b0ec617c4697b8fb9743bab6..af1f426300bc9d521d9bf11a3b922481f50e3dc7 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -566,10 +566,10 @@ fold_negate_expr_1 (location_t loc, tree t)
 
     case VECTOR_CST:
       {
-       int count = VECTOR_CST_NELTS (t), i;
-
-       auto_vec<tree, 32> elts (count);
-       for (i = 0; i < count; i++)
+       tree_vector_builder elts;
+       elts.new_unary_operation (type, t, true);
+       unsigned int count = elts.encoded_nelts ();
+       for (unsigned int i = 0; i < count; ++i)
          {
            tree elt = fold_negate_expr (loc, VECTOR_CST_ELT (t, i));
            if (elt == NULL_TREE)
@@ -577,7 +577,7 @@ fold_negate_expr_1 (location_t loc, tree t)
            elts.quick_push (elt);
          }
 
-       return build_vector (type, elts);
+       return elts.build ();
       }
 
     case COMPLEX_EXPR:
@@ -1121,6 +1121,27 @@ int_const_binop (enum tree_code code, const_tree arg1, const_tree arg2)
   return int_const_binop_1 (code, arg1, arg2, 1);
 }
 
+/* Return true if binary operation OP distributes over addition in operand
+   OPNO, with the other operand being held constant.  OPNO counts from 1.  */
+
+static bool
+distributes_over_addition_p (tree_code op, int opno)
+{
+  switch (op)
+    {
+    case PLUS_EXPR:
+    case MINUS_EXPR:
+    case MULT_EXPR:
+      return true;
+
+    case LSHIFT_EXPR:
+      return opno == 1;
+
+    default:
+      return false;
+    }
+}
+
 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
    constant.  We assume ARG1 and ARG2 have the same data type, or at least
    are the same kind of constant and the same machine mode.  Return zero if
@@ -1442,10 +1463,12 @@ const_binop (enum tree_code code, tree arg1, tree arg2)
       && TREE_CODE (arg2) == INTEGER_CST)
     {
       tree type = TREE_TYPE (arg1);
-      int count = VECTOR_CST_NELTS (arg1), i;
-
-      auto_vec<tree, 32> elts (count);
-      for (i = 0; i < count; i++)
+      bool step_ok_p = distributes_over_addition_p (code, 1);
+      tree_vector_builder elts;
+      if (!elts.new_unary_operation (type, arg1, step_ok_p))
+       return NULL_TREE;
+      unsigned int count = elts.encoded_nelts ();
+      for (unsigned int i = 0; i < count; ++i)
        {
          tree elem1 = VECTOR_CST_ELT (arg1, i);
 
@@ -1458,7 +1481,7 @@ const_binop (enum tree_code code, tree arg1, tree arg2)
          elts.quick_push (elt);
        }
 
-      return build_vector (type, elts);
+      return elts.build ();
     }
   return NULL_TREE;
 }
@@ -1649,10 +1672,12 @@ const_unop (enum tree_code code, tree type, tree arg0)
       else if (TREE_CODE (arg0) == VECTOR_CST)
        {
          tree elem;
-         unsigned count = VECTOR_CST_NELTS (arg0), i;
 
-         auto_vec<tree, 32> elements (count);
-         for (i = 0; i < count; i++)
+         /* This can cope with stepped encodings because ~x == -1 - x.  */
+         tree_vector_builder elements;
+         elements.new_unary_operation (type, arg0, true);
+         unsigned int i, count = elements.encoded_nelts ();
+         for (i = 0; i < count; ++i)
            {
              elem = VECTOR_CST_ELT (arg0, i);
              elem = const_unop (BIT_NOT_EXPR, TREE_TYPE (type), elem);
@@ -1661,7 +1686,7 @@ const_unop (enum tree_code code, tree type, tree arg0)
              elements.quick_push (elem);
            }
          if (i == count)
-           return build_vector (type, elements);
+           return elements.build ();
        }
       break;
 
@@ -2135,10 +2160,19 @@ fold_convert_const (enum tree_code code, tree type, tree arg1)
       if (TREE_CODE (arg1) == VECTOR_CST
          && TYPE_VECTOR_SUBPARTS (type) == VECTOR_CST_NELTS (arg1))
        {
-         int len = VECTOR_CST_NELTS (arg1);
          tree elttype = TREE_TYPE (type);
-         auto_vec<tree, 32> v (len);
-         for (int i = 0; i < len; ++i)
+         tree arg1_elttype = TREE_TYPE (TREE_TYPE (arg1));
+         /* We can't handle steps directly when extending, since the
+            values need to wrap at the original precision first.  */
+         bool step_ok_p
+           = (INTEGRAL_TYPE_P (elttype)
+              && INTEGRAL_TYPE_P (arg1_elttype)
+              && TYPE_PRECISION (elttype) <= TYPE_PRECISION (arg1_elttype));
+         tree_vector_builder v;
+         if (!v.new_unary_operation (type, arg1, step_ok_p))
+           return NULL_TREE;
+         unsigned int len = v.encoded_nelts ();
+         for (unsigned int i = 0; i < len; ++i)
            {
              tree elt = VECTOR_CST_ELT (arg1, i);
              tree cvt = fold_convert_const (code, elttype, elt);
@@ -2146,7 +2180,7 @@ fold_convert_const (enum tree_code code, tree type, tree arg1)
                return NULL_TREE;
              v.quick_push (cvt);
            }
-         return build_vector (type, v);
+         return v.build ();
        }
     }
   return NULL_TREE;
@@ -8832,7 +8866,6 @@ exact_inverse (tree type, tree cst)
   REAL_VALUE_TYPE r;
   tree unit_type;
   machine_mode mode;
-  unsigned vec_nelts, i;
 
   switch (TREE_CODE (cst))
     {
@@ -8846,12 +8879,14 @@ exact_inverse (tree type, tree cst)
 
     case VECTOR_CST:
       {
-       vec_nelts = VECTOR_CST_NELTS (cst);
        unit_type = TREE_TYPE (type);
        mode = TYPE_MODE (unit_type);
 
-       auto_vec<tree, 32> elts (vec_nelts);
-       for (i = 0; i < vec_nelts; i++)
+       tree_vector_builder elts;
+       if (!elts.new_unary_operation (type, cst, false))
+         return NULL_TREE;
+       unsigned int count = elts.encoded_nelts ();
+       for (unsigned int i = 0; i < count; ++i)
          {
            r = TREE_REAL_CST (VECTOR_CST_ELT (cst, i));
            if (!exact_real_inverse (mode, &r))
@@ -8859,7 +8894,7 @@ exact_inverse (tree type, tree cst)
            elts.quick_push (build_real (unit_type, r));
          }
 
-       return build_vector (type, elts);
+       return elts.build ();
       }
 
     default: