[Mesa-dev] [PATCH 3/3] i965: Emit MUL with a negated src for neg(mul(...)).

[Matt Turner]

total instructions in shared programs: 5932832 -> 5932736 (-0.00%)
instructions in affected programs:     8184 -> 8088 (-1.17%)
helped:                                52
HURT:                                  14
GAINED:                                1
---
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp   | 14 ++++++++++++++
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index b628bff..17849c7 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -630,6 +630,20 @@ fs_visitor::visit(ir_expression *ir)
 
    /* Deal with the real oddball stuff first */
    switch (ir->operation) {
+   case ir_unop_neg: {
+      if (!ir->type->is_float())
+         break;
+
+      ir_expression *mul = ir->operands[0]->as_expression();
+      if (mul && mul->operation == ir_binop_mul) {
+         mul->accept(this);
+         fs_inst *mul_inst = (fs_inst *) this->instructions.get_tail();
+         assert(mul_inst->opcode == BRW_OPCODE_MUL);
+
+         mul_inst->src[1].negate = true;
+      }
+      break;
+   }
    case ir_binop_add:
       if (brw->gen <= 5 && try_emit_line(ir))
          return;
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 5638105..2c21344 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -1309,6 +1309,25 @@ vec4_visitor::visit(ir_expression *ir)
    src_reg op[Elements(ir->operands)];
    vec4_instruction *inst;
 
+   switch (ir->operation) {
+   case ir_unop_neg: {
+      if (!ir->type->is_float())
+         break;
+
+      ir_expression *mul = ir->operands[0]->as_expression();
+      if (mul && mul->operation == ir_binop_mul) {
+         mul->accept(this);
+         vec4_instruction *mul_inst = (vec4_instruction *) this->instructions.get_tail();
+         assert(mul_inst->opcode == BRW_OPCODE_MUL);
+
+         mul_inst->src[1].negate = true;
+      }
+      break;
+   }
+   default:
+      break;
+   }
+
    if (ir->operation == ir_binop_add) {
       if (try_emit_mad(ir))
 	 return;
-- 
2.0.5