kc3-lang/angle/src/compiler/translator/tree_ops/d3d/ExpandIntegerPowExpressions.cpp

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• Hash : 382bf288
  Author :
  Date : 2020-12-24T23:56:39
  

  Organize AST transforms per backend
  
  Most of the AST transforms are written as a workaround to an issue that
  affects a single backend.  This change identifies such transforms and
  organizes them by backend.  They are then only built if the respective
  backend is.
  
  Additionally, about half of the GL transforms are due to mac
  workarounds, including the large RewriteRowMajorMatrices transform.
  Mac-specific workarounds are additionally only built on said platform.
  
  This change reduces the ANGLE binary size:
  
  - 106KB in a Vulkan-only build on Linux
  - 27KB in a GL-only build on Android (60KB on Linux)
  
  Bug: chromium:1084580
  Bug: chromium:1161513
  Change-Id: I64b334332c0d4f848756c6538af0d8d96864c7e9
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2601346
  Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  Reviewed-by: Tim Van Patten <timvp@google.com>
  

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• src/compiler/translator/tree_ops/d3d/ExpandIntegerPowExpressions.cpp

• //
  // Copyright 2016 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  // Implementation of the integer pow expressions HLSL bug workaround.
  // See header for more info.
  
  #include "compiler/translator/tree_ops/d3d/ExpandIntegerPowExpressions.h"
  
  #include <cmath>
  #include <cstdlib>
  
  #include "compiler/translator/tree_util/IntermNode_util.h"
  #include "compiler/translator/tree_util/IntermTraverse.h"
  
  namespace sh
  {
  
  namespace
  {
  
  class Traverser : public TIntermTraverser
  {
    public:
      ANGLE_NO_DISCARD static bool Apply(TCompiler *compiler,
                                         TIntermNode *root,
                                         TSymbolTable *symbolTable);
  
    private:
      Traverser(TSymbolTable *symbolTable);
      bool visitAggregate(Visit visit, TIntermAggregate *node) override;
      void nextIteration();
  
      bool mFound = false;
  };
  
  // static
  bool Traverser::Apply(TCompiler *compiler, TIntermNode *root, TSymbolTable *symbolTable)
  {
      Traverser traverser(symbolTable);
      do
      {
          traverser.nextIteration();
          root->traverse(&traverser);
          if (traverser.mFound)
          {
              if (!traverser.updateTree(compiler, root))
              {
                  return false;
              }
          }
      } while (traverser.mFound);
  
      return true;
  }
  
  Traverser::Traverser(TSymbolTable *symbolTable) : TIntermTraverser(true, false, false, symbolTable)
  {}
  
  void Traverser::nextIteration()
  {
      mFound = false;
  }
  
  bool Traverser::visitAggregate(Visit visit, TIntermAggregate *node)
  {
      if (mFound)
      {
          return false;
      }
  
      // Test 0: skip non-pow operators.
      if (node->getOp() != EOpPow)
      {
          return true;
      }
  
      const TIntermSequence *sequence = node->getSequence();
      ASSERT(sequence->size() == 2u);
      const TIntermConstantUnion *constantExponent = sequence->at(1)->getAsConstantUnion();
  
      // Test 1: check for a single constant.
      if (!constantExponent || constantExponent->getNominalSize() != 1)
      {
          return true;
      }
  
      float exponentValue = constantExponent->getConstantValue()->getFConst();
  
      // Test 2: exponentValue is in the problematic range.
      if (exponentValue < -5.0f || exponentValue > 9.0f)
      {
          return true;
      }
  
      // Test 3: exponentValue is integer or pretty close to an integer.
      if (std::abs(exponentValue - std::round(exponentValue)) > 0.0001f)
      {
          return true;
      }
  
      // Test 4: skip -1, 0, and 1
      int exponent = static_cast<int>(std::round(exponentValue));
      int n        = std::abs(exponent);
      if (n < 2)
      {
          return true;
      }
  
      // Potential problem case detected, apply workaround.
  
      TIntermTyped *lhs = sequence->at(0)->getAsTyped();
      ASSERT(lhs);
  
      TIntermDeclaration *lhsVariableDeclaration = nullptr;
      TVariable *lhsVariable =
          DeclareTempVariable(mSymbolTable, lhs, EvqTemporary, &lhsVariableDeclaration);
      insertStatementInParentBlock(lhsVariableDeclaration);
  
      // Create a chain of n-1 multiples.
      TIntermTyped *current = CreateTempSymbolNode(lhsVariable);
      for (int i = 1; i < n; ++i)
      {
          TIntermBinary *mul = new TIntermBinary(EOpMul, current, CreateTempSymbolNode(lhsVariable));
          mul->setLine(node->getLine());
          current = mul;
      }
  
      // For negative pow, compute the reciprocal of the positive pow.
      if (exponent < 0)
      {
          TConstantUnion *oneVal = new TConstantUnion();
          oneVal->setFConst(1.0f);
          TIntermConstantUnion *oneNode = new TIntermConstantUnion(oneVal, node->getType());
          TIntermBinary *div            = new TIntermBinary(EOpDiv, oneNode, current);
          current                       = div;
      }
  
      queueReplacement(current, OriginalNode::IS_DROPPED);
      mFound = true;
      return false;
  }
  
  }  // anonymous namespace
  
  bool ExpandIntegerPowExpressions(TCompiler *compiler, TIntermNode *root, TSymbolTable *symbolTable)
  {
      return Traverser::Apply(compiler, root, symbolTable);
  }
  
  }  // namespace sh
  

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