r300/compiler: Fix error in OMOD optimization

Classic compiler mistake.  In the example below, the OMOD optimization
was combining instructions 4 and 10, but since there was an instruction
(#8) in between them that wrote to the same registers as instruction 10,
instruction 11 was reading the wrong value.

Example of the mistake:

Before OMOD:
4: MAD temp[0].y, temp[3]._y__, const[0]._x__, const[0]._y__;
...
8: ADD temp[2].x, temp[1].x___, -temp[4].x___;
...
10: MUL temp[2].x, const[1].y___, temp[0].y___;
11: FRC temp[5].x, temp[2].x___;

After OMOD:
4: MAD temp[2].x / 8, temp[3]._y__, const[0]._x__, const[0]._y__;
...
8: ADD temp[2].x, temp[1].x___, -temp[4].x___;
...
11: FRC temp[5].x, temp[2].x___;

https://bugs.freedesktop.org/show_bug.cgi?id=41367

1 files changed, 16 insertions, 0 deletions

diff --git a/src/gallium/drivers/r300/compiler/radeon_optimize.c b/src/gallium/drivers/r300/compiler/radeon_optimize.c
index b7a0e20797c..2d799a6547a 100644
--- a/src/gallium/drivers/r300/compiler/radeon_optimize.c
+++ b/src/gallium/drivers/r300/compiler/radeon_optimize.c
@@ -681,6 +681,20 @@ static void omod_filter_reader_cb(
 	}
 }
 
+static void omod_filter_writer_cb(
+	void * userdata,
+	struct rc_instruction * inst,
+	rc_register_file file,
+	unsigned int index,
+	unsigned int mask)
+{
+	struct peephole_mul_cb_data * d = userdata;
+	if (file == d->Writer->File && index == d->Writer->Index &&
+					(mask & d->Writer->WriteMask)) {
+		d->Clobbered = 1;
+	}
+}
+
 static int peephole_mul_omod(
 	struct radeon_compiler * c,
 	struct rc_instruction * inst_mul,
@@ -788,6 +802,8 @@ static int peephole_mul_omod(
 							inst = inst->Prev) {
 			rc_for_all_reads_mask(inst, omod_filter_reader_cb,
 								&cb_data);
+			rc_for_all_writes_mask(inst, omod_filter_writer_cb,
+								&cb_data);
 			if (cb_data.Clobbered) {
 				break;
 			}