[Mesa-dev] [PATCH 09/12] glsl: Add a pass to propagate the "invariant" and "precise" qualifiers

[Francisco Jerez]

Jason Ekstrand <jason at jlekstrand.net> writes:

> ---
>  src/compiler/Makefile.sources              |   1 +
>  src/compiler/glsl/glsl_parser_extras.cpp   |   1 +
>  src/compiler/glsl/ir_optimization.h        |   1 +
>  src/compiler/glsl/propagate_invariance.cpp | 125 +++++++++++++++++++++++++++++
>  4 files changed, 128 insertions(+)
>  create mode 100644 src/compiler/glsl/propagate_invariance.cpp
>
> diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
> index 9f3bcf0..6ab0aa7 100644
> --- a/src/compiler/Makefile.sources
> +++ b/src/compiler/Makefile.sources
> @@ -129,6 +129,7 @@ LIBGLSL_FILES = \
>  	glsl/opt_tree_grafting.cpp \
>  	glsl/opt_vectorize.cpp \
>  	glsl/program.h \
> +	glsl/propagate_invariance.cpp \
>  	glsl/s_expression.cpp \
>  	glsl/s_expression.h
>  
> diff --git a/src/compiler/glsl/glsl_parser_extras.cpp b/src/compiler/glsl/glsl_parser_extras.cpp
> index 1c6cd43..9fcca21 100644
> --- a/src/compiler/glsl/glsl_parser_extras.cpp
> +++ b/src/compiler/glsl/glsl_parser_extras.cpp
> @@ -1885,6 +1885,7 @@ do_common_optimization(exec_list *ir, bool linked,
>        OPT(do_dead_functions, ir);
>        OPT(do_structure_splitting, ir);
>     }
> +   propagate_invariance(ir);
>     OPT(do_if_simplification, ir);
>     OPT(opt_flatten_nested_if_blocks, ir);
>     OPT(opt_conditional_discard, ir);
> diff --git a/src/compiler/glsl/ir_optimization.h b/src/compiler/glsl/ir_optimization.h
> index b56413a..4616f16 100644
> --- a/src/compiler/glsl/ir_optimization.h
> +++ b/src/compiler/glsl/ir_optimization.h
> @@ -138,6 +138,7 @@ bool lower_tess_level(gl_shader *shader);
>  bool lower_vertex_id(gl_shader *shader);
>  
>  bool lower_subroutine(exec_list *instructions, struct _mesa_glsl_parse_state *state);
> +void propagate_invariance(exec_list *instructions);
>  
>  ir_rvalue *
>  compare_index_block(exec_list *instructions, ir_variable *index,
> diff --git a/src/compiler/glsl/propagate_invariance.cpp b/src/compiler/glsl/propagate_invariance.cpp
> new file mode 100644
> index 0000000..820259e
> --- /dev/null
> +++ b/src/compiler/glsl/propagate_invariance.cpp
> @@ -0,0 +1,125 @@
> +/*
> + * Copyright © 2010 Intel Corporation
> + *

Wow, that's been a while ;)

> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + */
> +
> +/**
> + * \file propagate_invariance.cpp
> + * Propagate the "invariant" and "precise" qualifiers to variables used to
> + * compute invariant or precise values.
> + *
> + * The GLSL spec (depending on what version you read) says, among the
> + * conditions for geting bit-for-bit the same values on an invariant output:
> + *
> + *    "All operations in the consuming expressions and any intermediate
> + *    expressions must be the same, with the same order of operands and same
> + *    associativity, to give the same order of evaluation."
> + *
> + * This effectively means that if a variable is used to compute an invariant
> + * value then that variable becomes invariant.  The same should apply to the
> + * "precise" qualifier.
> + */
> +
> +#include "ir.h"
> +#include "ir_visitor.h"
> +#include "ir_rvalue_visitor.h"
> +#include "ir_optimization.h"
> +#include "compiler/glsl_types.h"
> +
> +namespace {
> +
> +class ir_invariance_propagation_visitor : public ir_hierarchical_visitor {
> +public:
> +   ir_invariance_propagation_visitor()
> +   {
> +      this->progress = false;
> +      this->dst_var = NULL;
> +   }
> +
> +   virtual ~ir_invariance_propagation_visitor()
> +   {
> +      /* empty */
> +   }
> +

Redundant destructor?

> +   virtual ir_visitor_status visit_enter(ir_assignment *ir);
> +   virtual ir_visitor_status visit_leave(ir_assignment *ir);
> +   virtual ir_visitor_status visit(ir_dereference_variable *ir);
> +
> +   ir_variable *dst_var;
> +   bool progress;
> +};
> +
> +} /* unnamed namespace */
> +
> +ir_visitor_status
> +ir_invariance_propagation_visitor::visit_enter(ir_assignment *ir)
> +{
> +   assert(this->dst_var == NULL);
> +   ir_variable *var = ir->lhs->variable_referenced();
> +   if (var->data.invariant || var->data.precise) {
> +      this->dst_var = var;
> +      return visit_continue;
> +   } else {
> +      return visit_continue_with_parent;
> +   }
> +}
> +
> +ir_visitor_status
> +ir_invariance_propagation_visitor::visit_leave(ir_assignment *ir)
> +{
> +   this->dst_var = NULL;
> +
> +   return visit_continue;
> +}
> +
> +ir_visitor_status
> +ir_invariance_propagation_visitor::visit(ir_dereference_variable *ir)
> +{
> +   if (this->dst_var == NULL)
> +      return visit_continue;
> +
> +   if (this->dst_var->data.invariant) {
> +      if (!ir->var->data.invariant)
> +         this->progress = true;
> +
> +      ir->var->data.invariant = true;
> +   }
> +
> +   if (this->dst_var->data.precise) {
> +      if (!ir->var->data.precise)
> +         this->progress = true;
> +
> +      ir->var->data.precise = true;
> +   }
> +
> +   return visit_continue;
> +}
> +
> +void
> +propagate_invariance(exec_list *instructions)
> +{
> +   ir_invariance_propagation_visitor visitor;
> +
> +   do {
> +      visitor.progress = false;
> +      visit_list_elements(&visitor, instructions);
> +   } while (visitor.progress);
> +}

Reviewed-by: Francisco Jerez <currojerez at riseup.net>

> -- 
> 2.5.0.400.gff86faf
>
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