[Mesa-dev] [PATCH 3/4] i965/vec4: Simplify visit(ir_expression *)'s result_src/dst setup.

[Kenneth Graunke]

Using dst_reg(this, ir->type) automatically sets the writemask to the
proper size for the type; src_reg(dst_reg) preserves that.  This should
be equivalent, but less code.

Note that src_reg(dst_reg) either uses SWIZZLE_XXXX or SWIZZLE_XYZW, so
the old code did need the manual writemask adjustment, since it
constructed the registers the other way around.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 683d1f5..93aa533 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -1259,8 +1259,6 @@ vec4_visitor::visit(ir_expression *ir)
 {
    unsigned int operand;
    src_reg op[Elements(ir->operands)];
-   src_reg result_src;
-   dst_reg result_dst;
    vec4_instruction *inst;
 
    if (ir->operation == ir_binop_add) {
@@ -1273,6 +1271,12 @@ vec4_visitor::visit(ir_expression *ir)
 	 return;
    }
 
+   /* Storage for our result.  Ideally for an assignment we'd be using
+    * the actual storage for the result here, instead.
+    */
+   dst_reg result_dst(this, ir->type);
+   src_reg result_src(result_dst);
+
    for (operand = 0; operand < ir->get_num_operands(); operand++) {
       this->result.file = BAD_FILE;
       ir->operands[operand]->accept(this);
@@ -1289,19 +1293,8 @@ vec4_visitor::visit(ir_expression *ir)
       assert(!ir->operands[operand]->type->is_matrix());
    }
 
-   /* Storage for our result.  Ideally for an assignment we'd be using
-    * the actual storage for the result here, instead.
-    */
-   result_src = src_reg(this, ir->type);
-   /* convenience for the emit functions below. */
-   result_dst = dst_reg(result_src);
    /* If nothing special happens, this is the result. */
    this->result = result_src;
-   /* Limit writes to the channels that will be used by result_src later.
-    * This does limit this temp's use as a temporary for multi-instruction
-    * sequences.
-    */
-   result_dst.writemask = (1 << ir->type->vector_elements) - 1;
 
    switch (ir->operation) {
    case ir_unop_logic_not:
-- 
2.1.2