Mostly revert r254296

r254296 added support for (const ...) wrappers around vectors,
but in the end the agreement was to use a variable-length
encoding of CONST_VECTOR (and VECTOR_CST) instead.  This patch
therefore reverts the bits that are no longer needed.

The rtl.texi part isn't a full revert, since r254296 also updated the
documentation to mention unspecs in address calculations, and to relax
the requirement that the mode had to be Pmode.

2018-01-10  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* doc/rtl.texi: Remove documentation of (const ...) wrappers
	for vectors, as a partial revert of r254296.
	* rtl.h (const_vec_p): Delete.
	(const_vec_duplicate_p): Don't test for vector CONSTs.
	(unwrap_const_vec_duplicate, const_vec_series_p): Likewise.
	* expmed.c (make_tree): Likewise.

	Revert:
	* common.md (E, F): Use CONSTANT_P instead of checking for
	CONST_VECTOR.
	* emit-rtl.c (gen_lowpart_common): Use const_vec_p instead of
	checking for CONST_VECTOR.

From-SVN: r256421

gcc/ChangeLog

+2018-01-10  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	* doc/rtl.texi: Remove documentation of (const ...) wrappers
+	for vectors, as a partial revert of r254296.
+	* rtl.h (const_vec_p): Delete.
+	(const_vec_duplicate_p): Don't test for vector CONSTs.
+	(unwrap_const_vec_duplicate, const_vec_series_p): Likewise.
+	* expmed.c (make_tree): Likewise.
+
+	Revert:
+	* common.md (E, F): Use CONSTANT_P instead of checking for
+	CONST_VECTOR.
+	* emit-rtl.c (gen_lowpart_common): Use const_vec_p instead of
+	checking for CONST_VECTOR.
+
 2018-01-09  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR middle-end/83575

gcc/common.md

@@ -80,14 +80,14 @@
 (define_constraint "E"
   "Matches a floating-point constant."
   (ior (match_test "CONST_DOUBLE_AS_FLOAT_P (op)")
-       (match_test "CONSTANT_P (op)
+       (match_test "GET_CODE (op) == CONST_VECTOR
 		    && GET_MODE_CLASS (GET_MODE (op)) == MODE_VECTOR_FLOAT")))
 
 ;; There is no longer a distinction between "E" and "F".
 (define_constraint "F"
   "Matches a floating-point constant."
   (ior (match_test "CONST_DOUBLE_AS_FLOAT_P (op)")
-       (match_test "CONSTANT_P (op)
+       (match_test "GET_CODE (op) == CONST_VECTOR
 		    && GET_MODE_CLASS (GET_MODE (op)) == MODE_VECTOR_FLOAT")))
 
 (define_constraint "X"

gcc/doc/rtl.texi

@@ -1875,18 +1875,12 @@ Usually that is the only mode for which a label is directly valid.
 
 @findex const
 @item (const:@var{m} @var{exp})
-Wraps an rtx computation @var{exp} whose inputs and result do not
-change during the execution of a thread.  There are two valid uses.
-The first is to represent a global or thread-local address calculation.
-In this case @var{exp} should contain @code{const_int},
-@code{symbol_ref}, @code{label_ref} or @code{unspec} expressions,
-combined with @code{plus} and @code{minus}.  Any such @code{unspec}s
-are target-specific and typically represent some form of relocation
-operator.  @var{m} should be a valid address mode.
-
-The second use of @code{const} is to wrap a vector operation.
-In this case @var{exp} must be a @code{vec_duplicate} or
-@code{vec_series} expression.
+Represents a constant that is the result of an assembly-time
+arithmetic computation.  The operand, @var{exp}, contains only
+@code{const_int}, @code{symbol_ref}, @code{label_ref} or @code{unspec}
+expressions, combined with @code{plus} and @code{minus}.  Any such
+@code{unspec}s are target-specific and typically represent some form
+of relocation operator.  @var{m} should be a valid address mode.
 
 @findex high
 @item (high:@var{m} @var{exp})

gcc/emit-rtl.c

@@ -1593,7 +1593,7 @@ gen_lowpart_common (machine_mode mode, rtx x)
 	return gen_rtx_fmt_e (GET_CODE (x), int_mode, XEXP (x, 0));
     }
   else if (GET_CODE (x) == SUBREG || REG_P (x)
-	   || GET_CODE (x) == CONCAT || const_vec_p (x)
+	   || GET_CODE (x) == CONCAT || GET_CODE (x) == CONST_VECTOR
 	   || CONST_DOUBLE_AS_FLOAT_P (x) || CONST_SCALAR_INT_P (x)
 	   || CONST_POLY_INT_P (x))
     return lowpart_subreg (mode, x, innermode);

gcc/expmed.c

@@ -5355,22 +5355,7 @@ make_tree (tree type, rtx x)
       return fold_convert (type, make_tree (t, XEXP (x, 0)));
 
     case CONST:
-      {
-	rtx op = XEXP (x, 0);
-	if (GET_CODE (op) == VEC_DUPLICATE)
-	  {
-	    tree elt_tree = make_tree (TREE_TYPE (type), XEXP (op, 0));
-	    return build_vector_from_val (type, elt_tree);
-	  }
-	if (GET_CODE (op) == VEC_SERIES)
-	  {
-	    tree itype = TREE_TYPE (type);
-	    tree base_tree = make_tree (itype, XEXP (op, 0));
-	    tree step_tree = make_tree (itype, XEXP (op, 1));
-	    return build_vec_series (type, base_tree, step_tree);
-	  }
-	return make_tree (type, op);
-      }
+      return make_tree (type, XEXP (x, 0));
 
     case SYMBOL_REF:
       t = SYMBOL_REF_DECL (x);

gcc/rtl.h

@@ -2935,24 +2935,14 @@ extern rtx shallow_copy_rtx (const_rtx CXX_MEM_STAT_INFO);
 extern int rtx_equal_p (const_rtx, const_rtx);
 extern bool rtvec_all_equal_p (const_rtvec);
 
-/* Return true if X is some form of vector constant.  */
-
-inline bool
-const_vec_p (const_rtx x)
-{
-  return VECTOR_MODE_P (GET_MODE (x)) && CONSTANT_P (x);
-}
-
 /* Return true if X is a vector constant with a duplicated element value.  */
 
 inline bool
 const_vec_duplicate_p (const_rtx x)
 {
-  return ((GET_CODE (x) == CONST_VECTOR
-	   && CONST_VECTOR_NPATTERNS (x) == 1
-	   && CONST_VECTOR_DUPLICATE_P (x))
-	  || (GET_CODE (x) == CONST
-	      && GET_CODE (XEXP (x, 0)) == VEC_DUPLICATE));
+  return (GET_CODE (x) == CONST_VECTOR
+	  && CONST_VECTOR_NPATTERNS (x) == 1
+	  && CONST_VECTOR_DUPLICATE_P (x));
 }
 
 /* Return true if X is a vector constant with a duplicated element value.
@@ -2962,20 +2952,11 @@ template <typename T>
 inline bool
 const_vec_duplicate_p (T x, T *elt)
 {
-  if (GET_CODE (x) == CONST_VECTOR
-      && CONST_VECTOR_NPATTERNS (x) == 1
-      && CONST_VECTOR_DUPLICATE_P (x))
+  if (const_vec_duplicate_p (x))
     {
       *elt = CONST_VECTOR_ENCODED_ELT (x, 0);
       return true;
     }
-  if (GET_CODE (x) == CONST
-      && GET_CODE (XEXP (x, 0)) == VEC_DUPLICATE
-      && !VECTOR_MODE_P (GET_MODE (XEXP (XEXP (x, 0), 0))))
-    {
-      *elt = XEXP (XEXP (x, 0), 0);
-      return true;
-    }
   return false;
 }
 
@@ -3002,12 +2983,8 @@ template <typename T>
 inline T
 unwrap_const_vec_duplicate (T x)
 {
-  if (GET_CODE (x) == CONST_VECTOR
-      && CONST_VECTOR_NPATTERNS (x) == 1
-      && CONST_VECTOR_DUPLICATE_P (x))
-    return CONST_VECTOR_ENCODED_ELT (x, 0);
-  if (GET_CODE (x) == CONST && GET_CODE (XEXP (x, 0)) == VEC_DUPLICATE)
-    return XEXP (XEXP (x, 0), 0);
+  if (const_vec_duplicate_p (x))
+    x = CONST_VECTOR_ELT (x, 0);
   return x;
 }
 
@@ -3030,12 +3007,6 @@ const_vec_series_p (const_rtx x, rtx *base_out, rtx *step_out)
       && CONST_VECTOR_NPATTERNS (x) == 1
       && !CONST_VECTOR_DUPLICATE_P (x))
     return const_vec_series_p_1 (x, base_out, step_out);
-  if (GET_CODE (x) == CONST && GET_CODE (XEXP (x, 0)) == VEC_SERIES)
-    {
-      *base_out = XEXP (XEXP (x, 0), 0);
-      *step_out = XEXP (XEXP (x, 0), 1);
-      return true;
-    }
   return false;
 }