Add a VEC_SERIES rtl code

This patch adds an rtl representation of a vector linear series
of the form:

  a[I] = BASE + I * STEP

Like vec_duplicate;

- the new rtx can be used for both constant and non-constant vectors
- when used for constant vectors it is wrapped in a (const ...)
- the constant form is only used for variable-length vectors;
  fixed-length vectors still use CONST_VECTOR

At the moment the code is restricted to integer elements, to avoid
concerns over floating-point rounding.

2017-11-01  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* doc/rtl.texi (vec_series): Document.
	(const): Say that the operand can be a vec_series.
	* rtl.def (VEC_SERIES): New rtx code.
	* rtl.h (const_vec_series_p_1): Declare.
	(const_vec_series_p): New function.
	* emit-rtl.h (gen_const_vec_series): Declare.
	(gen_vec_series): Likewise.
	* emit-rtl.c (const_vec_series_p_1, gen_const_vec_series)
	(gen_vec_series): Likewise.
	* optabs.c (expand_mult_highpart): Use gen_const_vec_series.
	* simplify-rtx.c (simplify_unary_operation): Handle negations
	of vector series.
	(simplify_binary_operation_series): New function.
	(simplify_binary_operation_1): Use it.  Handle VEC_SERIES.
	(test_vector_ops_series): New function.
	(test_vector_ops): Call it.
	* config/powerpcspe/altivec.md (altivec_lvsl): Use
	gen_const_vec_series.
	(altivec_lvsr): Likewise.
	* config/rs6000/altivec.md (altivec_lvsl, altivec_lvsr): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r254297

1 files changed, 45 insertions, 0 deletions

diff --git a/gcc/rtl.h b/gcc/rtl.h
index 373f8a2..a0f6965 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -2816,6 +2816,51 @@ unwrap_const_vec_duplicate (T x)
   return x;
 }
 
+/* In emit-rtl.c.  */
+extern bool const_vec_series_p_1 (const_rtx, rtx *, rtx *);
+
+/* Return true if X is a constant vector that contains a linear series
+   of the form:
+
+   { B, B + S, B + 2 * S, B + 3 * S, ... }
+
+   for a nonzero S.  Store B and S in *BASE_OUT and *STEP_OUT on sucess.  */
+
+inline bool
+const_vec_series_p (const_rtx x, rtx *base_out, rtx *step_out)
+{
+  if (GET_CODE (x) == CONST_VECTOR
+      && GET_MODE_CLASS (GET_MODE (x)) == MODE_VECTOR_INT)
+    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;
+}
+
+/* Return true if X is a vector that contains a linear series of the
+   form:
+
+   { B, B + S, B + 2 * S, B + 3 * S, ... }
+
+   where B and S are constant or nonconstant.  Store B and S in
+   *BASE_OUT and *STEP_OUT on sucess.  */
+
+inline bool
+vec_series_p (const_rtx x, rtx *base_out, rtx *step_out)
+{
+  if (GET_CODE (x) == VEC_SERIES)
+    {
+      *base_out = XEXP (x, 0);
+      *step_out = XEXP (x, 1);
+      return true;
+    }
+  return const_vec_series_p (x, base_out, step_out);
+}
+
 /* Return the unpromoted (outer) mode of SUBREG_PROMOTED_VAR_P subreg X.  */
 
 inline scalar_int_mode