Record the vector mask precision in stmt_vec_info

search_type_for_mask uses a worklist to search a chain of boolean
operations for a natural vector mask type.  This patch instead does
that in vect_determine_stmt_precisions, where we also look for
overpromoted integer operations.  We then only need to compute
the precision once and can cache it in the stmt_vec_info.

The new function vect_determine_mask_precision is supposed
to handle exactly the same cases as search_type_for_mask_1,
and in the same way.  There's a lot we could improve here,
but that's not stage 3 material.

I wondered about sharing mask_precision with other fields like
operation_precision, but in the end that seemed too dangerous.
We have patterns to convert between boolean and non-boolean
operations and it would be very easy to get mixed up about
which case the fields are describing.

2019-11-29  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vectorizer.h (stmt_vec_info::mask_precision): New field.
	(vect_use_mask_type_p): New function.
	* tree-vect-patterns.c (vect_init_pattern_stmt): Copy the
	mask precision to the pattern statement.
	(append_pattern_def_seq): Add a scalar_type_for_mask parameter
	and use it to initialize the new stmt's mask precision.
	(search_type_for_mask_1): Delete.
	(search_type_for_mask): Replace with...
	(integer_type_for_mask): ...this new function.  Use the information
	cached in the stmt_vec_info.
	(vect_recog_bool_pattern): Update accordingly.
	(build_mask_conversion): Pass the scalar type associated with the
	mask type to append_pattern_def_seq.
	(vect_recog_mask_conversion_pattern): Likewise.  Call
	integer_type_for_mask instead of search_type_for_mask.
	(vect_convert_mask_for_vectype): Call integer_type_for_mask instead
	of search_type_for_mask.
	(possible_vector_mask_operation_p): New function.
	(vect_determine_mask_precision): Likewise.
	(vect_determine_stmt_precisions): Call it.

From-SVN: r278850

gcc/ChangeLog

 2019-11-29  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* tree-vectorizer.h (stmt_vec_info::mask_precision): New field.
+	(vect_use_mask_type_p): New function.
+	* tree-vect-patterns.c (vect_init_pattern_stmt): Copy the
+	mask precision to the pattern statement.
+	(append_pattern_def_seq): Add a scalar_type_for_mask parameter
+	and use it to initialize the new stmt's mask precision.
+	(search_type_for_mask_1): Delete.
+	(search_type_for_mask): Replace with...
+	(integer_type_for_mask): ...this new function.  Use the information
+	cached in the stmt_vec_info.
+	(vect_recog_bool_pattern): Update accordingly.
+	(build_mask_conversion): Pass the scalar type associated with the
+	mask type to append_pattern_def_seq.
+	(vect_recog_mask_conversion_pattern): Likewise.  Call
+	integer_type_for_mask instead of search_type_for_mask.
+	(vect_convert_mask_for_vectype): Call integer_type_for_mask instead
+	of search_type_for_mask.
+	(possible_vector_mask_operation_p): New function.
+	(vect_determine_mask_precision): Likewise.
+	(vect_determine_stmt_precisions): Call it.
+
+2019-11-29  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* tree-vectorizer.h (get_mask_type_for_scalar_type): Replace
 	the slp_tree parameter with a group size parameter.
 	(vect_get_mask_type_for_stmt): Likewise.

gcc/tree-vectorizer.h

@@ -1089,6 +1089,23 @@ public:
   unsigned int operation_precision;
   signop operation_sign;
 
+  /* If the statement produces a boolean result, this value describes
+     how we should choose the associated vector type.  The possible
+     values are:
+
+     - an integer precision N if we should use the vector mask type
+       associated with N-bit integers.  This is only used if all relevant
+       input booleans also want the vector mask type for N-bit integers,
+       or if we can convert them into that form by pattern-matching.
+
+     - ~0U if we considered choosing a vector mask type but decided
+       to treat the boolean as a normal integer type instead.
+
+     - 0 otherwise.  This means either that the operation isn't one that
+       could have a vector mask type (and so should have a normal vector
+       type instead) or that we simply haven't made a choice either way.  */
+  unsigned int mask_precision;
+
   /* True if this is only suitable for SLP vectorization.  */
   bool slp_vect_only_p;
 };
@@ -1245,6 +1262,15 @@ nested_in_vect_loop_p (class loop *loop, stmt_vec_info stmt_info)
 	  && (loop->inner == (gimple_bb (stmt_info->stmt))->loop_father));
 }
 
+/* Return true if STMT_INFO should produce a vector mask type rather than
+   a normal nonmask type.  */
+
+static inline bool
+vect_use_mask_type_p (stmt_vec_info stmt_info)
+{
+  return stmt_info->mask_precision && stmt_info->mask_precision != ~0U;
+}
+
 /* Return TRUE if a statement represented by STMT_INFO is a part of a
    pattern.  */