src/third_party/angle/src/compiler/translator/RewriteElseBlocks.cpp

   1 //
   2 // Copyright (c) 2014 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 // RewriteElseBlocks.cpp: Implementation for tree transform to change
   7 //   all if-else blocks to if-if blocks.
   8 //
   9
  10 #include "compiler/translator/RewriteElseBlocks.h"
  11 #include "compiler/translator/NodeSearch.h"
  12 #include "compiler/translator/SymbolTable.h"
  13
  14 namespace sh
  15 {
  16
  17 TIntermSymbol *MakeNewTemporary(const TString &name, TBasicType type)
  18 {
  19     TType variableType(type, EbpHigh, EvqInternal);
  20     return new TIntermSymbol(-1, name, variableType);
  21 }
  22
  23 TIntermBinary *MakeNewBinary(TOperator op, TIntermTyped *left, TIntermTyped *right, const TType &resultType)
  24 {
  25     TIntermBinary *binary = new TIntermBinary(op);
  26     binary->setLeft(left);
  27     binary->setRight(right);
  28     binary->setType(resultType);
  29     return binary;
  30 }
  31
  32 TIntermUnary *MakeNewUnary(TOperator op, TIntermTyped *operand)
  33 {
  34     TIntermUnary *unary = new TIntermUnary(op, operand->getType());
  35     unary->setOperand(operand);
  36     return unary;
  37 }
  38
  39 ElseBlockRewriter::ElseBlockRewriter()
  40     : TIntermTraverser(true, false, true, false),
  41       mTemporaryIndex(0),
  42       mFunctionType(NULL)
  43 {}
  44
  45 bool ElseBlockRewriter::visitAggregate(Visit visit, TIntermAggregate *node)
  46 {
  47     switch (node->getOp())
  48     {
  49       case EOpSequence:
  50         if (visit == PostVisit)
  51         {
  52             for (size_t statementIndex = 0; statementIndex != node->getSequence().size(); statementIndex++)
  53             {
  54                 TIntermNode *statement = node->getSequence()[statementIndex];
  55                 TIntermSelection *selection = statement->getAsSelectionNode();
  56                 if (selection && selection->getFalseBlock() != NULL)
  57                 {
  58                     // Check for if / else if
  59                     TIntermSelection *elseIfBranch = selection->getFalseBlock()->getAsSelectionNode();
  60                     if (elseIfBranch)
  61                     {
  62                         selection->replaceChildNode(elseIfBranch, rewriteSelection(elseIfBranch));
  63                         delete elseIfBranch;
  64                     }
  65
  66                     node->getSequence()[statementIndex] = rewriteSelection(selection);
  67                     delete selection;
  68                 }
  69             }
  70         }
  71         break;
  72
  73       case EOpFunction:
  74         // Store the current function context (see comment below)
  75         mFunctionType = ((visit == PreVisit) ? &node->getType() : NULL);
  76         break;
  77
  78       default: break;
  79     }
  80
  81     return true;
  82 }
  83
  84 TIntermNode *ElseBlockRewriter::rewriteSelection(TIntermSelection *selection)
  85 {
  86     ASSERT(selection->getFalseBlock() != NULL);
  87
  88     TString temporaryName = "cond_" + str(mTemporaryIndex++);
  89     TIntermTyped *typedCondition = selection->getCondition()->getAsTyped();
  90     TType resultType(EbtBool, EbpUndefined);
  91     TIntermSymbol *conditionSymbolA = MakeNewTemporary(temporaryName, EbtBool);
  92     TIntermSymbol *conditionSymbolB = MakeNewTemporary(temporaryName, EbtBool);
  93     TIntermSymbol *conditionSymbolC = MakeNewTemporary(temporaryName, EbtBool);
  94     TIntermBinary *storeCondition = MakeNewBinary(EOpInitialize, conditionSymbolA,
  95                                                   typedCondition, resultType);
  96     TIntermUnary *negatedCondition = MakeNewUnary(EOpLogicalNot, conditionSymbolB);
  97     TIntermNode *negatedElse = NULL;
  98
  99     // crbug.com/346463
 100     // D3D generates error messages claiming a function has no return value, when rewriting
 101     // an if-else clause that returns something non-void in a function. By appending dummy
 102     // returns (that are unreachable) we can silence this compile error.
 103     if (mFunctionType && mFunctionType->getBasicType() != EbtVoid)
 104     {
 105         TString typeString = mFunctionType->getStruct() ? mFunctionType->getStruct()->name() :
 106             mFunctionType->getBasicString();
 107         TString rawText = "return (" + typeString + ")0";
 108         negatedElse = new TIntermRaw(*mFunctionType, rawText);
 109     }
 110
 111     TIntermSelection *falseBlock = new TIntermSelection(negatedCondition,
 112                                                         selection->getFalseBlock(), negatedElse);
 113     TIntermSelection *newIfElse = new TIntermSelection(conditionSymbolC,
 114                                                        selection->getTrueBlock(), falseBlock);
 115
 116     TIntermAggregate *declaration = new TIntermAggregate(EOpDeclaration);
 117     declaration->getSequence().push_back(storeCondition);
 118
 119     TIntermAggregate *block = new TIntermAggregate(EOpSequence);
 120     block->getSequence().push_back(declaration);
 121     block->getSequence().push_back(newIfElse);
 122
 123     return block;
 124 }
 125
 126 void RewriteElseBlocks(TIntermNode *node)
 127 {
 128     ElseBlockRewriter rewriter;
 129     node->traverse(&rewriter);
 130 }
 131
 132 }