[Mesa-dev] Add support for GLSL IR saturate()

[Abdiel Janulgue]

This patch series add the plumbing to support the GLSL IR instruction saturate().
Previously, saturate is implemented as min/max instructions. Most GPUs, however,
can probably perform saturate for free. With these changes, we can allow saturate
to be optimized as a single instruction.

In addition, the optimization try_emit_saturate was previously used to optimize
min/max operations to a saturate operation. It didn't work for code such as 
min(max(a, b), c) where (b == 0.0 and c < 1.0) and related cases.
With this infrastructure in place, we can optimize those operations easily in the
do_algebraic pass. This is done in the next patch set.

Abdiel Janulgue (11):
      glsl: Add ir_unop_saturate
      glsl: Add constant evaluation of ir_unop_saturate
      glsl: Add a pass to lower ir_unop_saturate to clamp(x, 0, 1)
      ir_to_mesa, glsl_to_tgsi: lower ir_unop_saturate
      ir_to_mesa, glsl_to_tgsi: Add support for ir_unop_saturate
      ir_to_mesa, glsl_to_tgsi: Remove try_emit_saturate
      i965/fs: Add support for ir_unop_saturate
      i965/vec4: Add support for ir_unop_saturate
      i965/fs: Remove try_emit_saturate
      i965/vec4: Remove try_emit_saturate
      glsl: Implement saturate as ir_binop_saturate

 src/glsl/ir.cpp                                          |  2 +
 src/glsl/ir.h                                            |  1 +
 src/glsl/ir_builder.cpp                                  |  6 +--
 src/glsl/ir_constant_expression.cpp                      |  6 +++
 src/glsl/ir_optimization.h                               |  1 +
 src/glsl/ir_validate.cpp                                 |  1 +
 src/glsl/lower_instructions.cpp                          | 29 ++++++++++++
 src/mesa/drivers/dri/i965/brw_fs.h                       |  1 -
 src/mesa/drivers/dri/i965/brw_fs_channel_expressions.cpp |  1 +
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp             | 41 ++---------------
 src/mesa/drivers/dri/i965/brw_vec4.h                     |  1 -
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp           | 25 ++--------
 src/mesa/program/ir_to_mesa.cpp                          | 59 ++++--------------------
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp               | 63 +++++---------------------
 14 files changed, 71 insertions(+), 166 deletions(-)