[gcc r14-5880] aarch64: Move and generalise vect_all_same

[Richard Sandiford <rsandifo@gcc.gnu.org>]

https://gcc.gnu.org/g:31e9074977bb7de83fa5d28d286323987d5d87f2

commit r14-5880-g31e9074977bb7de83fa5d28d286323987d5d87f2
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Mon Nov 27 14:44:02 2023 +0000

    aarch64: Move and generalise vect_all_same
    
    The fix for PR106329 needs a way of testing for a ptrue of a particular
    element size.  We already had such a function for svlast, so this patch
    moves it to common code and generalises it to work with all kinds of
    vectors.
    
    gcc/
            * config/aarch64/aarch64-sve-builtins.h (vector_cst_all_same): Declare.
            * config/aarch64/aarch64-sve-builtins.cc (vector_cst_all_same): New
            function, a generalized replacement of...
            * config/aarch64/aarch64-sve-builtins-base.cc
            (svlast_impl::vect_all_same): ...this.
            (svlast_impl::fold): Update accordingly.

Diff:
---
 gcc/config/aarch64/aarch64-sve-builtins-base.cc | 17 ++---------------
 gcc/config/aarch64/aarch64-sve-builtins.cc      | 20 ++++++++++++++++++++
 gcc/config/aarch64/aarch64-sve-builtins.h       |  2 ++
 3 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index 9010ecca6da..a6e527bedd1 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -1105,19 +1105,6 @@ public:
   bool is_lasta () const { return m_unspec == UNSPEC_LASTA; }
   bool is_lastb () const { return m_unspec == UNSPEC_LASTB; }
 
-  bool vect_all_same (tree v, int step) const
-  {
-    int i;
-    int nelts = vector_cst_encoded_nelts (v);
-    tree first_el = VECTOR_CST_ENCODED_ELT (v, 0);
-
-    for (i = 0; i < nelts; i += step)
-      if (!operand_equal_p (VECTOR_CST_ENCODED_ELT (v, i), first_el, 0))
-	return false;
-
-    return true;
-  }
-
   /* Fold a svlast{a/b} call with constant predicate to a BIT_FIELD_REF.
      BIT_FIELD_REF lowers to Advanced SIMD element extract, so we have to
      ensure the index of the element being accessed is in the range of a
@@ -1142,7 +1129,7 @@ public:
 	   without a linear search of the predicate vector:
 	   1.  LASTA if predicate is all true, return element 0.
 	   2.  LASTA if predicate all false, return element 0.  */
-	if (is_lasta () && vect_all_same (pred, step_1))
+	if (is_lasta () && vector_cst_all_same (pred, step_1))
 	  {
 	    b = build3 (BIT_FIELD_REF, TREE_TYPE (f.lhs), val,
 			bitsize_int (step * BITS_PER_UNIT), bitsize_int (0));
@@ -1152,7 +1139,7 @@ public:
 	/* Handle the all-false case for LASTB where SVE VL == 128b -
 	   return the highest numbered element.  */
 	if (is_lastb () && known_eq (BYTES_PER_SVE_VECTOR, 16)
-	    && vect_all_same (pred, step_1)
+	    && vector_cst_all_same (pred, step_1)
 	    && integer_zerop (VECTOR_CST_ENCODED_ELT (pred, 0)))
 	  {
 	    b = build3 (BIT_FIELD_REF, TREE_TYPE (f.lhs), val,
diff --git a/gcc/config/aarch64/aarch64-sve-builtins.cc b/gcc/config/aarch64/aarch64-sve-builtins.cc
index 161a14edde7..b61156302cf 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins.cc
@@ -2541,6 +2541,26 @@ function_checker::check ()
   return shape->check (*this);
 }
 
+/* Return true if V is a vector constant and if, for every in-range integer I,
+   element STEP*I is equal to element 0.  */
+bool
+vector_cst_all_same (tree v, unsigned int step)
+{
+  if (TREE_CODE (v) != VECTOR_CST)
+    return false;
+
+  /* VECTOR_CST_NELTS_PER_PATTERN applies to any multiple of
+     VECTOR_CST_NPATTERNS.  */
+  unsigned int lcm = least_common_multiple (step, VECTOR_CST_NPATTERNS (v));
+  unsigned int nelts = lcm * VECTOR_CST_NELTS_PER_PATTERN (v);
+  tree first_el = VECTOR_CST_ENCODED_ELT (v, 0);
+  for (unsigned int i = 0; i < nelts; i += step)
+    if (!operand_equal_p (VECTOR_CST_ENCODED_ELT (v, i), first_el, 0))
+      return false;
+
+  return true;
+}
+
 gimple_folder::gimple_folder (const function_instance &instance, tree fndecl,
 			      gimple_stmt_iterator *gsi_in, gcall *call_in)
   : function_call_info (gimple_location (call_in), instance, fndecl),
diff --git a/gcc/config/aarch64/aarch64-sve-builtins.h b/gcc/config/aarch64/aarch64-sve-builtins.h
index a301570b82e..d646df1c026 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins.h
+++ b/gcc/config/aarch64/aarch64-sve-builtins.h
@@ -672,6 +672,8 @@ extern tree acle_vector_types[MAX_TUPLE_SIZE][NUM_VECTOR_TYPES + 1];
 extern tree acle_svpattern;
 extern tree acle_svprfop;
 
+bool vector_cst_all_same (tree, unsigned int);
+
 /* Return the ACLE type svbool_t.  */
 inline tree
 get_svbool_t (void)