[PATCH][v3] tree-optimization/114921 - _Float16 -> __bf16 isn't noop

[PATCH][v3] tree-optimization/114921 - _Float16 -> __bf16 isn't noop

[Richard Biener]

The vectorizer handles a _Float16 to __bf16 conversion through
vectorizable_assignment, thinking it's a noop.  The following
fixes this by requiring the same vector component mode when
checking for CONVERT_EXPR_CODE_P, being stricter than for
VIEW_CONVERT_EXPR.

This variant splits the check for VIEW_CONVERT_EXPR and
CONVERT_EXPR_CODE_P since it otherwise regresses gcc.dg/vect/vect-120.c.

	PR tree-optimization/114921
	* tree-vect-stmts.cc (vectorizable_assignment): Require
	same vector component modes for input and output for
	CONVERT_EXPR_CODE_P.
---
 gcc/tree-vect-stmts.cc | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index f8d8636b139..7e571968a59 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -5955,14 +5955,17 @@ vectorizable_assignment (vec_info *vinfo,
   if (!vectype_in)
     vectype_in = get_vectype_for_scalar_type (vinfo, TREE_TYPE (op), slp_node);
 
-  /* We can handle NOP_EXPR conversions that do not change the number
-     of elements or the vector size.  */
-  if ((CONVERT_EXPR_CODE_P (code)
-       || code == VIEW_CONVERT_EXPR)
-      && (!vectype_in
-	  || maybe_ne (TYPE_VECTOR_SUBPARTS (vectype_in), nunits)
-	  || maybe_ne (GET_MODE_SIZE (TYPE_MODE (vectype)),
-		       GET_MODE_SIZE (TYPE_MODE (vectype_in)))))
+  /* We can handle VIEW_CONVERT conversions that do not change the number
+     of elements or the vector size or other conversions when the component
+     mode keeps the same.  */
+  if (!vectype_in
+      || maybe_ne (TYPE_VECTOR_SUBPARTS (vectype_in), nunits)
+      || (code == VIEW_CONVERT_EXPR
+	  && maybe_ne (GET_MODE_SIZE (TYPE_MODE (vectype)),
+		       GET_MODE_SIZE (TYPE_MODE (vectype_in))))
+      || (CONVERT_EXPR_CODE_P (code)
+	  && (TYPE_MODE (TREE_TYPE (vectype))
+	      != TYPE_MODE (TREE_TYPE (vectype_in)))))
     return false;
 
   if (VECTOR_BOOLEAN_TYPE_P (vectype) != VECTOR_BOOLEAN_TYPE_P (vectype_in))
-- 
2.35.3