gallium: Disambiguate TGSI_OPCODE_IF.

TGSI_OPCODE_IF condition had two possible interpretations:

- src.x != 0.0f

  - Mesa statetracker when PIPE_SHADER_CAP_INTEGERS was false either for
    vertex and fragment shaders
  - gallivm/llvmpipe
  - postprocess
  - vl state tracker
  - vega state tracker
  - most old drivers
  - old internal state trackers
  - many graw examples

- src.x != 0U

  - Mesa statetracker when PIPE_SHADER_CAP_INTEGERS was true for both
    vertex and fragment shaders
  - tgsi_exec/softpipe
  - r600
  - radeonsi
  - nv50

And drivers that use draw module also were a mess (because Mesa would
emit float IFs, but draw module supports native integers so it would
interpret IF arg as integers...)

This sort of works if the source argument is limited to float +0.0f or
+1.0f, integer 0, but would fail if source is float -0.0f, or integer in
the float NaN range.  It could also fail if source is integer 1, and
hardware flushes denormalized numbers to zero.

But with this change there are now two opcodes, IF and UIF, with clear
meaning.

Drivers that do not support native integers do not need to worry about
UIF.  However, for backwards compatibility with old state trackers and
examples, it is advisable that native integer capable drivers also
support the float IF opcode.

I tried to implement this for r600 and radeonsi based on the surrounding
code.  I couldn't do this for nouveau, so I just shunted IF/UIF
together, which matches the current behavior.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Marek Olšák <maraeo@gmail.com>

v2:
- Incorporate Roland's feedback.
- Fix r600_shader.c merge conflict.
- Fix typo in radeon, spotted by Michel Dänzer.
- Incorporte  Christoph Bumiller's patch to handle TGSI_OPCODE_IF(float)
  properly in nv50/ir.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/gallium/include/pipe/p_shader_tokens.h b/src/gallium/include/pipe/p_shader_tokens.h
index 6fcd151aecc..50de2d370a1 100644
--- a/src/gallium/include/pipe/p_shader_tokens.h
+++ b/src/gallium/include/pipe/p_shader_tokens.h
@@ -335,7 +335,7 @@ struct tgsi_property_data {
 #define TGSI_OPCODE_TXL                 72
 #define TGSI_OPCODE_BRK                 73
 #define TGSI_OPCODE_IF                  74
-                                /* gap */
+#define TGSI_OPCODE_UIF                 75
 #define TGSI_OPCODE_ELSE                77
 #define TGSI_OPCODE_ENDIF               78
                                 /* gap */