The Tor Browser: gfx/angle/src/compiler/UnfoldShortCircuit.cpp@141e0f1194b1

     1 //

     2 // Copyright (c) 2002-2013 The ANGLE Project Authors. All rights reserved.

     3 // Use of this source code is governed by a BSD-style license that can be

     4 // found in the LICENSE file.

     5 //

     6 // UnfoldShortCircuit is an AST traverser to output short-circuiting operators as if-else statements.

     7 // The results are assigned to s# temporaries, which are used by the main translator instead of

     8 // the original expression.

     9 //

    11 #include "compiler/UnfoldShortCircuit.h"

    13 #include "compiler/InfoSink.h"

    14 #include "compiler/OutputHLSL.h"

    16 namespace sh

    17 {

    18 UnfoldShortCircuit::UnfoldShortCircuit(TParseContext &context, OutputHLSL *outputHLSL) : mContext(context), mOutputHLSL(outputHLSL)

    19 {

    20     mTemporaryIndex = 0;

    21 }

    23 void UnfoldShortCircuit::traverse(TIntermNode *node)

    24 {

    25     int rewindIndex = mTemporaryIndex;

    26     node->traverse(this);

    27     mTemporaryIndex = rewindIndex;

    28 }

    30 bool UnfoldShortCircuit::visitBinary(Visit visit, TIntermBinary *node)

    31 {

    32     TInfoSinkBase &out = mOutputHLSL->getBodyStream();

    34     switch (node->getOp())

    35     {

    36       case EOpLogicalOr:

    37         // "x || y" is equivalent to "x ? true : y", which unfolds to "bool s; if(x) s = true; else s = y;",

    38         // and then further simplifies down to "bool s = x; if(!s) s = y;".

    39         {

    40             int i = mTemporaryIndex;

    42             out << "bool s" << i << ";\n";

    44             out << "{\n";

    46             mTemporaryIndex = i + 1;

    47             node->getLeft()->traverse(this);

    48             out << "s" << i << " = ";

    49             mTemporaryIndex = i + 1;

    50             node->getLeft()->traverse(mOutputHLSL);

    51             out << ";\n";

    52             out << "if(!s" << i << ")\n"

    53                    "{\n";

    54             mTemporaryIndex = i + 1;

    55             node->getRight()->traverse(this);

    56             out << "    s" << i << " = ";

    57             mTemporaryIndex = i + 1;

    58             node->getRight()->traverse(mOutputHLSL);

    59             out << ";\n"

    60                    "}\n";

    62             out << "}\n";

    64             mTemporaryIndex = i + 1;

    65         }

    66         return false;

    67       case EOpLogicalAnd:

    68         // "x && y" is equivalent to "x ? y : false", which unfolds to "bool s; if(x) s = y; else s = false;",

    69         // and then further simplifies down to "bool s = x; if(s) s = y;".

    70         {

    71             int i = mTemporaryIndex;

    73             out << "bool s" << i << ";\n";

    75             out << "{\n";

    77             mTemporaryIndex = i + 1;

    78             node->getLeft()->traverse(this);

    79             out << "s" << i << " = ";

    80             mTemporaryIndex = i + 1;

    81             node->getLeft()->traverse(mOutputHLSL);

    82             out << ";\n";

    83             out << "if(s" << i << ")\n"

    84                    "{\n";

    85             mTemporaryIndex = i + 1;

    86             node->getRight()->traverse(this);

    87             out << "    s" << i << " = ";

    88             mTemporaryIndex = i + 1;

    89             node->getRight()->traverse(mOutputHLSL);

    90             out << ";\n"

    91                    "}\n";

    93             out << "}\n";

    95             mTemporaryIndex = i + 1;

    96         }

    97         return false;

    98       default:

    99         return true;

   100     }

   101 }

   103 bool UnfoldShortCircuit::visitSelection(Visit visit, TIntermSelection *node)

   104 {

   105     TInfoSinkBase &out = mOutputHLSL->getBodyStream();

   107     // Unfold "b ? x : y" into "type s; if(b) s = x; else s = y;"

   108     if (node->usesTernaryOperator())

   109     {

   110         int i = mTemporaryIndex;

   112         out << mOutputHLSL->typeString(node->getType()) << " s" << i << ";\n";

   114         out << "{\n";

   116         mTemporaryIndex = i + 1;

   117         node->getCondition()->traverse(this);

   118         out << "if(";

   119         mTemporaryIndex = i + 1;

   120         node->getCondition()->traverse(mOutputHLSL);

   121         out << ")\n"

   122                "{\n";

   123         mTemporaryIndex = i + 1;

   124         node->getTrueBlock()->traverse(this);

   125         out << "    s" << i << " = ";

   126         mTemporaryIndex = i + 1;

   127         node->getTrueBlock()->traverse(mOutputHLSL);

   128         out << ";\n"

   129                "}\n"

   130                "else\n"

   131                "{\n";

   132         mTemporaryIndex = i + 1;

   133         node->getFalseBlock()->traverse(this);

   134         out << "    s" << i << " = ";

   135         mTemporaryIndex = i + 1;

   136         node->getFalseBlock()->traverse(mOutputHLSL);

   137         out << ";\n"

   138                "}\n";

   140         out << "}\n";

   142         mTemporaryIndex = i + 1;

   143     }

   145     return false;

   146 }

   148 bool UnfoldShortCircuit::visitLoop(Visit visit, TIntermLoop *node)

   149 {

   150     int rewindIndex = mTemporaryIndex;

   152     if (node->getInit())

   153     {

   154         node->getInit()->traverse(this);

   155     }

   157     if (node->getCondition())

   158     {

   159         node->getCondition()->traverse(this);

   160     }

   162     if (node->getExpression())

   163     {

   164         node->getExpression()->traverse(this);

   165     }

   167     mTemporaryIndex = rewindIndex;

   169     return false;

   170 }

   172 int UnfoldShortCircuit::getNextTemporaryIndex()

   173 {

   174     return mTemporaryIndex++;

   175 }

   176 }

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