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      1 /*
      2  * Copyright  2010 Intel Corporation
      3  *
      4  * Permission is hereby granted, free of charge, to any person obtaining a
      5  * copy of this software and associated documentation files (the "Software"),
      6  * to deal in the Software without restriction, including without limitation
      7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      8  * and/or sell copies of the Software, and to permit persons to whom the
      9  * Software is furnished to do so, subject to the following conditions:
     10  *
     11  * The above copyright notice and this permission notice (including the next
     12  * paragraph) shall be included in all copies or substantial portions of the
     13  * Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     21  * DEALINGS IN THE SOFTWARE.
     22  */
     23 
     24 /**
     25  * \file lower_noise.cpp
     26  * IR lower pass to remove noise opcodes.
     27  *
     28  * \author Ian Romanick <ian.d.romanick (at) intel.com>
     29  */
     30 
     31 #include "ir.h"
     32 #include "ir_rvalue_visitor.h"
     33 
     34 class lower_noise_visitor : public ir_rvalue_visitor {
     35 public:
     36    lower_noise_visitor() : progress(false)
     37    {
     38       /* empty */
     39    }
     40 
     41    void handle_rvalue(ir_rvalue **rvalue)
     42    {
     43       if (!*rvalue)
     44 	 return;
     45 
     46       ir_expression *expr = (*rvalue)->as_expression();
     47       if (!expr)
     48 	 return;
     49 
     50       /* In the future, ir_unop_noise may be replaced by a call to a function
     51        * that implements noise.  No hardware has a noise instruction.
     52        */
     53       if (expr->operation == ir_unop_noise) {
     54 	 *rvalue = ir_constant::zero(ralloc_parent(expr), expr->type);
     55 	 this->progress = true;
     56       }
     57    }
     58 
     59    bool progress;
     60 };
     61 
     62 
     63 bool
     64 lower_noise(exec_list *instructions)
     65 {
     66    lower_noise_visitor v;
     67 
     68    visit_list_elements(&v, instructions);
     69 
     70    return v.progress;
     71 }
     72