tree: Add vector_element_bits(_tree) [PR94980 1/3]

A lot of code that wants to know the number of bits in a vector
element gets that information from the element's TYPE_SIZE,
which is always equal to TYPE_SIZE_UNIT * BITS_PER_UNIT.
This doesn't work for SVE and AVX512-style packed boolean vectors,
where several elements can occupy a single byte.

This patch introduces a new pair of helpers for getting the true
(possibly sub-byte) size.  I made a token attempt to convert obvious
element size calculations, but I'm sure I missed some.

2020-05-12  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR tree-optimization/94980
	* tree.h (vector_element_bits, vector_element_bits_tree): Declare.
	* tree.c (vector_element_bits, vector_element_bits_tree): New.
	* match.pd: Use the new functions instead of determining the
	vector element size directly from TYPE_SIZE(_UNIT).
	* tree-vect-data-refs.c (vect_gather_scatter_fn_p): Likewise.
	* tree-vect-patterns.c (vect_recog_mask_conversion_pattern): Likewise.
	* tree-vect-stmts.c (vect_is_simple_cond): Likewise.
	* tree-vect-generic.c (expand_vector_piecewise): Likewise.
	(expand_vector_conversion): Likewise.
	(expand_vector_addition): Likewise for a TYPE_SIZE_UNIT used as
	a divisor.  Convert the dividend to bits to compensate.
	* tree-vect-loop.c (vectorizable_live_operation): Call
	vector_element_bits instead of open-coding it.

1 files changed, 7 insertions, 12 deletions

diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
index 8b00f32..126e906 100644
--- a/gcc/tree-vect-generic.c
+++ b/gcc/tree-vect-generic.c
@@ -276,8 +276,7 @@ expand_vector_piecewise (gimple_stmt_iterator *gsi, elem_op_func f,
   tree part_width = TYPE_SIZE (inner_type);
   tree index = bitsize_int (0);
   int nunits = nunits_for_known_piecewise_op (type);
-  int delta = tree_to_uhwi (part_width)
-	      / tree_to_uhwi (TYPE_SIZE (TREE_TYPE (type)));
+  int delta = tree_to_uhwi (part_width) / vector_element_bits (type);
   int i;
   location_t loc = gimple_location (gsi_stmt (*gsi));
 
@@ -357,8 +356,7 @@ expand_vector_addition (gimple_stmt_iterator *gsi,
 			elem_op_func f, elem_op_func f_parallel,
 			tree type, tree a, tree b, enum tree_code code)
 {
-  int parts_per_word = UNITS_PER_WORD
-	  	       / tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (type)));
+  int parts_per_word = BITS_PER_WORD / vector_element_bits (type);
 
   if (INTEGRAL_TYPE_P (TREE_TYPE (type))
       && parts_per_word >= 4
@@ -1727,19 +1725,17 @@ expand_vector_conversion (gimple_stmt_iterator *gsi)
   optab optab1 = unknown_optab;
 
   gcc_checking_assert (VECTOR_TYPE_P (ret_type) && VECTOR_TYPE_P (arg_type));
-  gcc_checking_assert (tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (ret_type))));
-  gcc_checking_assert (tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (arg_type))));
   if (INTEGRAL_TYPE_P (TREE_TYPE (ret_type))
       && SCALAR_FLOAT_TYPE_P (TREE_TYPE (arg_type)))
     code = FIX_TRUNC_EXPR;
   else if (INTEGRAL_TYPE_P (TREE_TYPE (arg_type))
 	   && SCALAR_FLOAT_TYPE_P (TREE_TYPE (ret_type)))
     code = FLOAT_EXPR;
-  if (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (ret_type)))
-      < tree_to_uhwi (TYPE_SIZE (TREE_TYPE (arg_type))))
+  unsigned int ret_elt_bits = vector_element_bits (ret_type);
+  unsigned int arg_elt_bits = vector_element_bits (arg_type);
+  if (ret_elt_bits < arg_elt_bits)
     modifier = NARROW;
-  else if (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (ret_type)))
-	   > tree_to_uhwi (TYPE_SIZE (TREE_TYPE (arg_type))))
+  else if (ret_elt_bits > arg_elt_bits)
     modifier = WIDEN;
 
   if (modifier == NONE && (code == FIX_TRUNC_EXPR || code == FLOAT_EXPR))
@@ -1902,8 +1898,7 @@ expand_vector_conversion (gimple_stmt_iterator *gsi)
 	      tree part_width = TYPE_SIZE (compute_type);
 	      tree index = bitsize_int (0);
 	      int nunits = nunits_for_known_piecewise_op (arg_type);
-	      int delta = tree_to_uhwi (part_width)
-			  / tree_to_uhwi (TYPE_SIZE (TREE_TYPE (arg_type)));
+	      int delta = tree_to_uhwi (part_width) / arg_elt_bits;
 	      int i;
 	      location_t loc = gimple_location (gsi_stmt (*gsi));