nv50,nvc0: handle SQRT lowering inside the driver

First off, st/mesa lowers DSQRT incorrectly (it uses CMP to attempt to
find out whether the input is less than 0). Secondly the current
approach (x * rsq(x)) behaves poorly for x = inf - a NaN is produced
instead of inf.

Instead we switch to the less accurate rcp(rsq(x)) method - this behaves
nicely for all valid inputs. We still don't do this for DSQRT since the
RSQ/RCP ops are *really* inaccurate, and don't even have Newton-Raphson
steps right now. Eventually we should have a separate library function
for DSQRT that does it more precisely (and perhaps move this lowering to
the post-opt phase).

This fixes a number of dEQP precision tests that were expecting better
behavior for infinite inputs.

Signed-off-by: Ilia Mirkin <[email protected]>
Reviewed-by: Samuel Pitoiset <[email protected]>
Tested-by: Samuel Pitoiset <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/gallium/drivers/nouveau/nv50/nv50_screen.c b/src/gallium/drivers/nouveau/nv50/nv50_screen.c
index 28e0ed3c225..5836bb23764 100644
--- a/src/gallium/drivers/nouveau/nv50/nv50_screen.c
+++ b/src/gallium/drivers/nouveau/nv50/nv50_screen.c
@@ -305,7 +305,7 @@ nv50_screen_get_shader_param(struct pipe_screen *pscreen, unsigned shader,
    case PIPE_SHADER_CAP_TGSI_CONT_SUPPORTED:
       return 1;
    case PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED:
-      return 0;
+      return 1;
    case PIPE_SHADER_CAP_SUBROUTINES:
       return 0; /* please inline, or provide function declarations */
    case PIPE_SHADER_CAP_INTEGERS: