Mesa (18.2): st/nine: Clamp RCP when 0*inf!=0

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Module: Mesa
Branch: 18.2
Commit: 98fd4107c464567bb7508676a263c64f66d7d412
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=98fd4107c464567bb7508676a263c64f66d7d412

Author: Axel Davy <davyaxel0 at gmail.com>
Date:   Fri Jan 27 23:13:29 2017 +0100

st/nine: Clamp RCP when 0*inf!=0

Tests done on several devices of all 3 vendors and
of different generations showed that there are several
ways of handling infs and NaN for d3d9.

Tests showed Intel on windows does always clamp
RCP, RSQ and LOG (thus preventing inf/nan generation),
for all shader versions (some vendor behaviours vary
with shader versions).
Doing this in nine avoids 0*inf issues for drivers
that can't generate 0*inf=0 (which is controled by
TGSI's MUL_ZERO_WINS).

For now clamp for all drivers. An ulterior optimization
would be to avoid clamping for drivers with MUL_ZERO_WINS
for the specific shader versions where NV or AMD don't
clamp.

LOG and RSQ being already clamped, this patch only
clamps RCP.

Fixes: https://github.com/iXit/Mesa-3D/issues/316

Signed-off-by: Axel Davy <davyaxel0 at gmail.com>
CC: <mesa-stable at lists.freedesktop.org>
(cherry picked from commit 7ee5e5e239a5528c6eed2d1bb47b48434de74a6e)

---

 src/gallium/state_trackers/nine/nine_shader.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/gallium/state_trackers/nine/nine_shader.c b/src/gallium/state_trackers/nine/nine_shader.c
index 7db07d8f69..5b8ad3f161 100644
--- a/src/gallium/state_trackers/nine/nine_shader.c
+++ b/src/gallium/state_trackers/nine/nine_shader.c
@@ -2273,6 +2273,18 @@ DECL_SPECIAL(POW)
     return D3D_OK;
 }
 
+DECL_SPECIAL(RCP)
+{
+    struct ureg_program *ureg = tx->ureg;
+    struct ureg_dst dst = tx_dst_param(tx, &tx->insn.dst[0]);
+    struct ureg_src src = tx_src_param(tx, &tx->insn.src[0]);
+    struct ureg_dst tmp = tx_scratch(tx);
+    ureg_RCP(ureg, tmp, src);
+    ureg_MIN(ureg, tmp, ureg_imm1f(ureg, FLT_MAX), ureg_src(tmp));
+    ureg_MAX(ureg, dst, ureg_imm1f(ureg, -FLT_MAX), ureg_src(tmp));
+    return D3D_OK;
+}
+
 DECL_SPECIAL(RSQ)
 {
     struct ureg_program *ureg = tx->ureg;
@@ -2909,7 +2921,7 @@ static const struct sm1_op_info inst_table[] =
     _OPI(SUB, NOP, V(0,0), V(3,0), V(0,0), V(3,0), 1, 2, SPECIAL(SUB)), /* 3 */
     _OPI(MAD, MAD, V(0,0), V(3,0), V(0,0), V(3,0), 1, 3, NULL), /* 4 */
     _OPI(MUL, MUL, V(0,0), V(3,0), V(0,0), V(3,0), 1, 2, NULL), /* 5 */
-    _OPI(RCP, RCP, V(0,0), V(3,0), V(0,0), V(3,0), 1, 1, NULL), /* 6 */
+    _OPI(RCP, RCP, V(0,0), V(3,0), V(0,0), V(3,0), 1, 1, SPECIAL(RCP)), /* 6 */
     _OPI(RSQ, RSQ, V(0,0), V(3,0), V(0,0), V(3,0), 1, 1, SPECIAL(RSQ)), /* 7 */
     _OPI(DP3, DP3, V(0,0), V(3,0), V(0,0), V(3,0), 1, 2, NULL), /* 8 */
     _OPI(DP4, DP4, V(0,0), V(3,0), V(0,0), V(3,0), 1, 2, NULL), /* 9 */