r300/compiler: optimize CMP for vertex shaders a bit

1 files changed, 9 insertions, 20 deletions

diff --git a/src/mesa/drivers/dri/r300/compiler/radeon_program_alu.c b/src/mesa/drivers/dri/r300/compiler/radeon_program_alu.c
index f5b7d57eab7..fced31d6cb9 100644
--- a/src/mesa/drivers/dri/r300/compiler/radeon_program_alu.c
+++ b/src/mesa/drivers/dri/r300/compiler/radeon_program_alu.c
@@ -511,37 +511,26 @@ static void transform_r300_vertex_CMP(struct radeon_compiler* c,
 {
 	/* There is no decent CMP available, so let's rig one up.
 	 * CMP is defined as dst = src0 < 0.0 ? src1 : src2
-	 * The following sequence consumes two temps and three extra slots,
+	 * The following sequence consumes two temps and two extra slots
+	 * (the second temp and the second slot is consumed by transform_LRP),
 	 * but should be equivalent:
 	 *
 	 * SLT tmp0, src0, 0.0
-	 * SGE tmp1, src0, 0.0
-	 * MUL tmp0, tmp0, src1
-	 * MAD dst, src2, tmp1, tmp0
+	 * LRP dst, tmp0, src1, src2
 	 *
-	 * Yes, I know, I'm a mad scientist. ~ C. */
+	 * Yes, I know, I'm a mad scientist. ~ C. & M. */
 	int tempreg0 = rc_find_free_temporary(c);
-	int tempreg1 = rc_find_free_temporary(c);
 
 	/* SLT tmp0, src0, 0.0 */
 	emit2(c, inst->Prev, RC_OPCODE_SLT, 0,
 		dstreg(RC_FILE_TEMPORARY, tempreg0),
 		inst->U.I.SrcReg[0], builtin_zero);
 
-	/* SGE tmp1, src0, 0.0 */
-	emit2(c, inst->Prev, RC_OPCODE_SGE, 0,
-		dstreg(RC_FILE_TEMPORARY, tempreg1),
-		inst->U.I.SrcReg[0], builtin_zero);
-
-	/* MUL tmp0, tmp0, src1 */
-	emit2(c, inst->Prev, RC_OPCODE_MUL, 0,
-		dstreg(RC_FILE_TEMPORARY, tempreg0),
-		srcreg(RC_FILE_TEMPORARY, tempreg0), inst->U.I.SrcReg[1]);
-
-	/* MAD dst, src2, tmp1, tmp0 */
-	emit3(c, inst->Prev, RC_OPCODE_MAD, inst->U.I.SaturateMode,
-		inst->U.I.DstReg,
-		inst->U.I.SrcReg[2], srcreg(RC_FILE_TEMPORARY, tempreg1), srcreg(RC_FILE_TEMPORARY, tempreg0));
+	/* LRP dst, tmp0, src1, src2 */
+	transform_LRP(c,
+		emit3(c, inst->Prev, RC_OPCODE_LRP, 0,
+		      inst->U.I.DstReg,
+		      srcreg(RC_FILE_TEMPORARY, tempreg0), inst->U.I.SrcReg[1],  inst->U.I.SrcReg[2]));
 
 	rc_remove_instruction(inst);
 }