Be stricter about CONST_VECTOR operands

The recent gen_vec_duplicate patches used CONST_VECTOR for all
constants, but the documentation says:

  @findex const_vector
  @item (const_vector:@var{m} [@var{x0} @var{x1} @dots{}])
  Represents a vector constant.  The square brackets stand for the vector
  containing the constant elements.  @var{x0}, @var{x1} and so on are
  the @code{const_int}, @code{const_double} or @code{const_fixed} elements.

Both the AArch32 and AArch64 ports relied on the elements having
this form and would ICE if the element was something like a CONST
instead.  This showed up as a failure in vect-126.c for both arm-eabi
and aarch64-elf (but not aarch64-linux-gnu, which is what the series
was tested on).

The two obvious options were to redefine CONST_VECTOR to accept all
constants or make gen_vec_duplicate honour the existing documentation.
It looks like other code also assumes that integer CONST_VECTORs contain
CONST_INTs, so the patch does the latter.

I deliberately didn't add an assert to gen_const_vec_duplicate
because it looks like the SPU port *does* expect to be able to create
CONST_VECTORs of symbolic constants.

Also, I think the list above should include const_wide_int for vectors
of TImode and wider.

The new routine takes a mode for consistency with the generators,
and because I think it does make sense to accept all constants for
variable-length:

    (const (vec_duplicate ...))

rather than have some rtxes for which we instead use:

    (vec_duplicate (const ...))


2017-11-09  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* doc/rtl.texi (const_vector): Say that elements can be
	const_wide_ints too.
	* emit-rtl.h (valid_for_const_vec_duplicate_p): Declare.
	* emit-rtl.c (valid_for_const_vec_duplicate_p): New function.
	(gen_vec_duplicate): Use it instead of CONSTANT_P.
	* optabs.c (expand_vector_broadcast): Likewise.

From-SVN: r254586

gcc/ChangeLog

 2017-11-09  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	* doc/rtl.texi (const_vector): Say that elements can be
+	const_wide_ints too.
+	* emit-rtl.h (valid_for_const_vec_duplicate_p): Declare.
+	* emit-rtl.c (valid_for_const_vec_duplicate_p): New function.
+	(gen_vec_duplicate): Use it instead of CONSTANT_P.
+	* optabs.c (expand_vector_broadcast): Likewise.
+
+2017-11-09  Richard Sandiford  <richard.sandiford@linaro.org>
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 

gcc/doc/rtl.texi

@@ -1625,7 +1625,8 @@ accessed with @code{CONST_FIXED_VALUE_LOW}.
 @item (const_vector:@var{m} [@var{x0} @var{x1} @dots{}])
 Represents a vector constant.  The square brackets stand for the vector
 containing the constant elements.  @var{x0}, @var{x1} and so on are
-the @code{const_int}, @code{const_double} or @code{const_fixed} elements.
+the @code{const_int}, @code{const_wide_int}, @code{const_double} or
+@code{const_fixed} elements.
 
 The number of units in a @code{const_vector} is obtained with the macro
 @code{CONST_VECTOR_NUNITS} as in @code{CONST_VECTOR_NUNITS (@var{v})}.

gcc/emit-rtl.c

@@ -5772,6 +5772,17 @@ init_emit (void)
 #endif
 }
 
+/* Return true if X is a valid element for a duplicated vector constant
+   of the given mode.  */
+
+bool
+valid_for_const_vec_duplicate_p (machine_mode, rtx x)
+{
+  return (CONST_SCALAR_INT_P (x)
+	  || CONST_DOUBLE_AS_FLOAT_P (x)
+	  || CONST_FIXED_P (x));
+}
+
 /* Like gen_const_vec_duplicate, but ignore const_tiny_rtx.  */
 
 static rtx
@@ -5807,7 +5818,7 @@ gen_const_vec_duplicate (machine_mode mode, rtx elt)
 rtx
 gen_vec_duplicate (machine_mode mode, rtx x)
 {
-  if (CONSTANT_P (x))
+  if (valid_for_const_vec_duplicate_p (mode, x))
     return gen_const_vec_duplicate (mode, x);
   return gen_rtx_VEC_DUPLICATE (mode, x);
 }

gcc/emit-rtl.h

@@ -438,6 +438,7 @@ get_max_uid (void)
   return crtl->emit.x_cur_insn_uid;
 }
 
+extern bool valid_for_const_vec_duplicate_p (machine_mode, rtx);
 extern rtx gen_const_vec_duplicate (machine_mode, rtx);
 extern rtx gen_vec_duplicate (machine_mode, rtx);
 

gcc/optabs.c

@@ -377,7 +377,7 @@ expand_vector_broadcast (machine_mode vmode, rtx op)
 
   gcc_checking_assert (VECTOR_MODE_P (vmode));
 
-  if (CONSTANT_P (op))
+  if (valid_for_const_vec_duplicate_p (vmode, op))
     return gen_const_vec_duplicate (vmode, op);
 
   /* ??? If the target doesn't have a vec_init, then we have no easy way