glsl: Remove opt_conditional_discard().

The nir_opt_conditional_discard pass is called anyway and covers
discard/demote/terminate.

iris shader-db:

total instructions in shared programs: 8933422 -> 8933426 (<.01%)
instructions in affected programs: 48 -> 52 (8.33%)
helped: 0
HURT: 4

which is a synmark shader going from 12 to 13 instrs.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17664>

src/compiler/glsl/glsl_parser_extras.cpp

@@ -2390,7 +2390,6 @@ do_common_optimization(exec_list *ir, bool linked,
    OPT(propagate_invariance, ir);
    OPT(do_if_simplification, ir);
    OPT(opt_flatten_nested_if_blocks, ir);
-   OPT(opt_conditional_discard, ir);
    OPT(do_copy_propagation_elements, ir);
 
    if (options->OptimizeForAOS && !linked)

src/compiler/glsl/ir_optimization.h

@@ -87,7 +87,6 @@ bool ir_constant_fold(ir_rvalue **rvalue);
 bool do_rebalance_tree(exec_list *instructions);
 bool do_algebraic(exec_list *instructions, bool native_integers,
                   const struct gl_shader_compiler_options *options);
-bool opt_conditional_discard(exec_list *instructions);
 bool do_constant_folding(exec_list *instructions);
 bool do_constant_variable(exec_list *instructions);
 bool do_constant_variable_unlinked(exec_list *instructions);

src/compiler/glsl/meson.build

@@ -178,7 +178,6 @@ files_libglsl = files(
   'lower_output_reads.cpp',
   'opt_algebraic.cpp',
   'opt_array_splitting.cpp',
-  'opt_conditional_discard.cpp',
   'opt_constant_folding.cpp',
   'opt_constant_propagation.cpp',
   'opt_constant_variable.cpp',

src/compiler/glsl/opt_conditional_discard.cpp

@@ -1,88 +0,0 @@
-/*
- * Copyright © 2014 Intel Corporation
- *
- * 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 opt_conditional_discard.cpp
- *
- * Replace
- *
- *    if (cond) discard;
- *
- * with
- *
- *    (discard <condition>)
- */
-
-#include "compiler/glsl_types.h"
-#include "ir.h"
-
-namespace {
-
-class opt_conditional_discard_visitor : public ir_hierarchical_visitor {
-public:
-   opt_conditional_discard_visitor()
-   {
-      progress = false;
-   }
-
-   ir_visitor_status visit_leave(ir_if *);
-
-   bool progress;
-};
-
-} /* anonymous namespace */
-
-bool
-opt_conditional_discard(exec_list *instructions)
-{
-   opt_conditional_discard_visitor v;
-   v.run(instructions);
-   return v.progress;
-}
-
-ir_visitor_status
-opt_conditional_discard_visitor::visit_leave(ir_if *ir)
-{
-   /* Look for "if (...) discard" with no else clause or extra statements. */
-   if (ir->then_instructions.is_empty() ||
-       !ir->then_instructions.get_head_raw()->next->is_tail_sentinel() ||
-       !((ir_instruction *) ir->then_instructions.get_head_raw())->as_discard() ||
-       !ir->else_instructions.is_empty())
-      return visit_continue;
-
-   /* Move the condition and replace the ir_if with the ir_discard. */
-   ir_discard *discard = (ir_discard *) ir->then_instructions.get_head_raw();
-   if (!discard->condition)
-      discard->condition = ir->condition;
-   else {
-      void *ctx = ralloc_parent(ir);
-      discard->condition = new(ctx) ir_expression(ir_binop_logic_and,
-                                                  ir->condition,
-                                                  discard->condition);
-   }
-   ir->replace_with(discard);
-
-   progress = true;
-
-   return visit_continue;
-}