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

[Gert Wollny]

This patch is based on
https://lists.freedesktop.org/archives/mesa-dev/2018-February/185805.html

Dave Airlie:

 "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.

  GCM seems to move some of the copies into other basic blocks,
  if we don't allow this to happen then it doesn't seem to schedule
  them badly.

  Everything I've read on SSA/phi copies say they have to happen
  in parallel, so keeping them in the same basic block seems like
  a good way to keep some of that property."

This patch differs from the one proposed by Dave in that it only adds 
the NF_DONT_MOVE flag to copy_move instructions that are created by split_phi* 
and that are located in loops.

Fixes piglit: tests/shaders/ssa/fs-while-loop-rotate-value.shader_test
(no regressions in the shader set). It also fixes all failing tests from 

  dEQP-GLES3.functional.shaders.loops.*

Signed-off-by: Gert Wollny <gw.fossdev at gmail.com>
---
 src/gallium/drivers/r600/sb/sb_ra_init.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/gallium/drivers/r600/sb/sb_ra_init.cpp b/src/gallium/drivers/r600/sb/sb_ra_init.cpp
index 985e179452..c557b86871 100644
--- a/src/gallium/drivers/r600/sb/sb_ra_init.cpp
+++ b/src/gallium/drivers/r600/sb/sb_ra_init.cpp
@@ -545,10 +545,13 @@ void ra_split::split_phi_src(container_node *loc, container_node *c,
 			continue;
 
 		value *t = sh.create_temp_value();
+		alu_node* n = sh.create_copy_mov(t, v);
+		if (loop)
+			n->flags |= NF_DONT_MOVE;
 		if (loop && id == 0)
-			loc->insert_before(sh.create_copy_mov(t, v));
+			loc->insert_before(n);
 		else
-			loc->push_back(sh.create_copy_mov(t, v));
+			loc->push_back(n);
 		v = t;
 
 		sh.coal.add_edge(v, d, coalescer::phi_cost);
@@ -566,9 +569,10 @@ void ra_split::split_phi_dst(node* loc, container_node *c, bool loop) {
 
 		value *t = sh.create_temp_value();
 		node *cp = sh.create_copy_mov(v, t);
-		if (loop)
+		if (loop) {
+			cp->flags |= NF_DONT_MOVE;
 			static_cast<container_node*>(loc)->push_front(cp);
-		else
+		} else
 			loc->insert_after(cp);
 		v = t;
 	}
-- 
2.16.1