This allows the backend to decide if it does not
want saturates, or if it wants to combine min/max
together by itself.
Usefull for drivers that implement saturate with min/max
as it can allow for some optimizations by min/max-pruning.
Drivers like freedreno and vc4 will benefit.
---
I have not made any drivers set the option.
Probably some pipe-cap or something is needed
in gallium to allow this?
I could possibly find time to do a follow-up
patch for this if someone leads me in the right direction.
saturate() in ir_builder generates ir_unop_saturate unconditionally.
If someone comes along later and does saturate()
in some optimization pass, whithout checking the options,
they will mess up possible optimizations for some backends.
The cleanest way I could find for always doing the right
thing was to write a lowering pass in opt_algebraic to
lower ir_unop_sature into max(min(x, 1), 0);
The other alternative would be to rewrite the saturate()
to use max(min(x, 1), 0) like it used to, and rewrite the part
in opt_algebraic that detects hand-rolled saturate
to instead do: new expression(ir_unop_saturate, x);
---
src/glsl/opt_algebraic.cpp | 12 ++++++++++++
src/mesa/main/mtypes.h | 1 +
2 files changed, 13 insertions(+)
diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index 430f5cb..af1f544 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -682,6 +682,10 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
if (ir->type->base_type != GLSL_TYPE_FLOAT)
break;
+ // Only emit saturate if the option is set
+ if (options->EmitNoSaturate)
+ break;
+
/* Replace min(max) operations and its commutative combinations with
* a saturate operation
*/
@@ -787,6 +791,14 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
return ir->operands[2];
break;
+ case ir_unop_saturate:
+ if (options->EmitNoSaturate)
+ return expr(ir_binop_max,
+ expr(ir_binop_min, ir->operands[0],
+ new(mem_ctx) ir_constant(1.0f)),
+ new(mem_ctx) ir_constant(0.0f));
+ break;
+
default:
break;
}
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 7389baa..922e88b 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2990,6 +2990,7 @@ struct gl_shader_compiler_options
GLboolean EmitNoMainReturn; /**< Emit CONT/RET opcodes? */
GLboolean EmitNoNoise; /**< Emit NOISE opcodes? */
GLboolean EmitNoPow; /**< Emit POW opcodes? */
+ GLboolean EmitNoSaturate; /**< Emit SATURATE opcodes? */
GLboolean LowerClipDistance; /**< Lower gl_ClipDistance from float[8] to
vec4[2]? */
/**
--
2.0.3
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