[Mesa-dev] [PATCH] r600/sb: fix rotated register in while loop (v3)

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

A bunch of CTS tests led me to write
tests/shaders/ssa/fs-while-loop-rotate-value.shader_test
which r600/sb always fell over on.

This patch fixes it, but I'll probably never be 100% sure why.

Anyways what appears to be happening is when gcm is scheduling
the copy_movs used for phis, we have 4 copy_movs in the scheduling
queue, one of them releases a new copy_mov and it gets pushed
to the the front of the scheduling queue, but for correctness
we rely on the previous copy_movs getting emitted first. This
places copy_movs in order on the list.

So if the list is empty, it puts it at the front, if the list
has just copy_movs in it, it goes to the end, otherwise
we iterate the list and insert it between the copy_movs and
subsequent instructions.

I've added the additional check here that if the src[0]
of the copy mov has a constraint (which will be true for the
(copy) MOV R1.x.2, t10 case but not for MOV t20, cases,
then we should schedule those early, but the others late.

v2: wrong direction.

v3: back to v1 + changes

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 src/gallium/drivers/r600/sb/sb_gcm.cpp | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/r600/sb/sb_gcm.cpp b/src/gallium/drivers/r600/sb/sb_gcm.cpp
index 7776a10fc86..0c715b24dfb 100644
--- a/src/gallium/drivers/r600/sb/sb_gcm.cpp
+++ b/src/gallium/drivers/r600/sb/sb_gcm.cpp
@@ -637,8 +637,23 @@ void gcm::add_ready(node *n) {
 	sched_queue_id sq = sh.get_queue_id(n);
 	if (n->flags & NF_SCHEDULE_EARLY)
 		bu_ready_early[sq].push_back(n);
-	else if (sq == SQ_ALU && n->is_copy_mov())
-		bu_ready[sq].push_front(n);
+	else if (sq == SQ_ALU && n->is_copy_mov()) {
+		if (bu_ready[sq].empty() || n->src[0]->constraint)
+			bu_ready[sq].push_front(n);
+		else {
+			bool inserted = false;
+			for (sched_queue::iterator I = bu_ready[sq].begin(), E = bu_ready[sq].end(); I != E; I++) {
+				node *a = *I;
+				if (!a->is_copy_mov()) {
+					bu_ready[sq].insert(I, n);
+					inserted = true;
+					break;
+				}
+			}
+			if (!inserted)
+				bu_ready[sq].push_back(n);
+		}
+	}
 	else if (n->is_alu_inst()) {
 		alu_node *a = static_cast<alu_node*>(n);
 		if (a->bc.op_ptr->flags & AF_PRED && a->dst[2]) {
-- 
2.14.3