Make gimple_build_vector take a tree_vector_builder

This patch changes gimple_build_vector so that it takes a
tree_vector_builder instead of a size and a vector of trees.

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

gcc/
	* vector-builder.h (vector_builder::derived): New const overload.
	(vector_builder::elt): New function.
	* tree-vector-builder.h (tree_vector_builder::type): New function.
	(tree_vector_builder::apply_step): Declare.
	* tree-vector-builder.c (tree_vector_builder::apply_step): New
	function.
	* gimple-fold.h (tree_vector_builder): Declare.
	(gimple_build_vector): Take a tree_vector_builder instead of a
	type and vector of elements.
	* gimple-fold.c (gimple_build_vector): Likewise.
	* tree-vect-loop.c (get_initial_def_for_reduction): Update call
	accordingly.
	(get_initial_defs_for_reduction): Likewise.
	(vectorizable_induction): Likewise.

From-SVN: r255478

1 files changed, 37 insertions, 0 deletions

diff --git a/gcc/vector-builder.h b/gcc/vector-builder.h
index ae30b3bb..0edd6f5 100644
--- a/gcc/vector-builder.h
+++ b/gcc/vector-builder.h
@@ -68,6 +68,10 @@ along with GCC; see the file COPYING3.  If not see
 	  given integral_p (ELT1) && integral_p (ELT2).  There is no fixed
 	  choice of StepType.
 
+      T apply_step (T base, unsigned int factor, StepType step) const;
+
+	  Return a vector element with the value BASE + FACTOR * STEP.
+
       bool can_elide_p (T elt) const;
 
 	  Return true if we can drop element ELT, even if the retained
@@ -91,6 +95,7 @@ public:
   unsigned int nelts_per_pattern () const { return m_nelts_per_pattern; }
   unsigned int encoded_nelts () const;
   bool encoded_full_vector_p () const;
+  T elt (unsigned int) const;
 
   void finalize ();
 
@@ -163,6 +168,38 @@ vector_builder<T, Derived>::new_vector (unsigned int full_nelts,
   this->truncate (0);
 }
 
+/* Return the value of vector element I, which might or might not be
+   encoded explicitly.  */
+
+template<typename T, typename Derived>
+T
+vector_builder<T, Derived>::elt (unsigned int i) const
+{
+  /* This only makes sense if the encoding has been fully populated.  */
+  gcc_checking_assert (encoded_nelts () <= this->length ());
+
+  /* First handle elements that are already present in the underlying
+     vector, regardless of whether they're part of the encoding or not.  */
+  if (i < this->length ())
+    return (*this)[i];
+
+  /* Identify the pattern that contains element I and work out the index of
+     the last encoded element for that pattern.  */
+  unsigned int pattern = i % m_npatterns;
+  unsigned int count = i / m_npatterns;
+  unsigned int final_i = encoded_nelts () - m_npatterns + pattern;
+  T final = (*this)[final_i];
+
+  /* If there are no steps, the final encoded value is the right one.  */
+  if (m_nelts_per_pattern <= 2)
+    return final;
+
+  /* Otherwise work out the value from the last two encoded elements.  */
+  T prev = (*this)[final_i - m_npatterns];
+  return derived ()->apply_step (final, count - 2,
+				 derived ()->step (prev, final));
+}
+
 /* Change the encoding to NPATTERNS patterns of NELTS_PER_PATTERN each,
    but without changing the underlying vector.  */