[Mesa-dev] [PATCH] radeonsi/nir: disable GLSL IR loop unrolling

[Timothy Arceri]

Delaying unrolling and allowing NIR to do it instead has been shown
to result in better code in drivers such as i965. shader-db results
appear to should the same is true for radeonsi.

The other advantage is that using NIR unrolling improves compile
times significantly.

Totals from affected shaders:
SGPRS: 9624 -> 10016 (4.07 %)
VGPRS: 6800 -> 6464 (-4.94 %)
Spilled SGPRs: 0 -> 2 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 0 -> 0 (0.00 %) dwords per thread
Code Size: 359176 -> 332264 (-7.49 %) bytes
LDS: 0 -> 0 (0.00 %) blocks
Max Waves: 1355 -> 1432 (5.68 %)
Wait states: 0 -> 0 (0.00 %)
---
 src/gallium/drivers/radeonsi/si_get.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/gallium/drivers/radeonsi/si_get.c b/src/gallium/drivers/radeonsi/si_get.c
index ef03a962d1..18d9cec414 100644
--- a/src/gallium/drivers/radeonsi/si_get.c
+++ b/src/gallium/drivers/radeonsi/si_get.c
@@ -437,6 +437,8 @@ static int si_get_shader_param(struct pipe_screen* pscreen,
 	case PIPE_SHADER_CAP_MAX_SHADER_IMAGES:
 		return SI_NUM_IMAGES;
 	case PIPE_SHADER_CAP_MAX_UNROLL_ITERATIONS_HINT:
+		if (sscreen->debug_flags & DBG(NIR))
+			return 0;
 		return 32;
 	case PIPE_SHADER_CAP_PREFERRED_IR:
 		if (sscreen->debug_flags & DBG(NIR))
-- 
2.14.3