On 08/02/2016 00:21, Ilia Mirkin wrote:
On Sun, Feb 7, 2016 at 6:13 PM, Axel Davy <axel.d...@ens.fr> wrote:
SQRT is not supported everywhere, so replace
it by RSQ + RCP
Signed-off-by: Axel Davy <axel.d...@ens.fr>
---
src/gallium/state_trackers/nine/nine_ff.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/gallium/state_trackers/nine/nine_ff.c
b/src/gallium/state_trackers/nine/nine_ff.c
index a5466a7..894fc63 100644
--- a/src/gallium/state_trackers/nine/nine_ff.c
+++ b/src/gallium/state_trackers/nine/nine_ff.c
@@ -563,7 +563,8 @@ nine_ff_build_vs(struct NineDevice9 *device, struct
vs_build_ctx *vs)
struct ureg_src cPsz2 = ureg_DECL_constant(ureg, 27);
ureg_DP3(ureg, tmp_x, ureg_src(r[1]), ureg_src(r[1]));
- ureg_SQRT(ureg, tmp_y, _X(tmp));
+ ureg_RSQ(ureg, tmp_y, _X(tmp));
+ ureg_RCP(ureg, tmp_y, _Y(tmp));
I'd recommend doing
ureg_MUL(ureg, tmp_y, _Y(tmp), _X(tmp))
instead. That should be (a) more numerically stable (rcp doesn't have
great precision), and (b) not blow up for 0.
Ok for the precision, but I'm not sure for 0
With the mul version, with 0, it ends up computing inf * 0 = NaN,
whereas with the rcp version, it does 1/inf == 0 (as far as I know),
which is the expected result.
ureg_MAD(ureg, tmp_x, _Y(tmp), _YYYY(cPsz2), _XXXX(cPsz2));
ureg_MAD(ureg, tmp_x, _Y(tmp), _X(tmp), _WWWW(cPsz1));
ureg_RCP(ureg, tmp_x, ureg_src(tmp));
--
2.7.0
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