[Mesa-dev] [PATCH] r600/sb: Do not distribute neg in expr_handler::fold_assoc() when folding multiplications.

[Xavier B]

From: xavier <xavierb at gmail.com>

Previously it was doing this transformation for a Trine 3 shader:
     MUL     R6.x.12,    R13.x.23, 0.5|3f000000
-    MULADD     R4.x.12,    -R6.x.12, 2|40000000, 1|3f800000
+    MULADD     R4.x.12,    -R13.x.23, -1|bf800000, 1|3f800000

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94412
Signed-off-by: Xavier Bouchoux <xavierb at gmail.com>
---
 src/gallium/drivers/r600/sb/sb_expr.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/r600/sb/sb_expr.cpp b/src/gallium/drivers/r600/sb/sb_expr.cpp
index 556a05d..3dd3a48 100644
--- a/src/gallium/drivers/r600/sb/sb_expr.cpp
+++ b/src/gallium/drivers/r600/sb/sb_expr.cpp
@@ -598,9 +598,13 @@ bool expr_handler::fold_assoc(alu_node *n) {
 
 	unsigned op = n->bc.op;
 	bool allow_neg = false, cur_neg = false;
+	bool distribute_neg = false;
 
 	switch(op) {
 	case ALU_OP2_ADD:
+		distribute_neg = true;
+		allow_neg = true;
+		break;
 	case ALU_OP2_MUL:
 	case ALU_OP2_MUL_IEEE:
 		allow_neg = true;
@@ -632,7 +636,7 @@ bool expr_handler::fold_assoc(alu_node *n) {
 		if (v1->is_const()) {
 			literal arg = v1->get_const_value();
 			apply_alu_src_mod(a->bc, 1, arg);
-			if (cur_neg)
+			if (cur_neg && distribute_neg)
 				arg.f = -arg.f;
 
 			if (a == n)
@@ -660,7 +664,7 @@ bool expr_handler::fold_assoc(alu_node *n) {
 		if (v0->is_const()) {
 			literal arg = v0->get_const_value();
 			apply_alu_src_mod(a->bc, 0, arg);
-			if (cur_neg)
+			if (cur_neg && distribute_neg)
 				arg.f = -arg.f;
 
 			if (last_arg == 0) {
-- 
2.7.2