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

• Show log

  Commit

• 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>
  

Download

• src/compiler/translator/tree_ops/d3d/BreakVariableAliasingInInnerLoops.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.
  //
  
  // BreakVariableAliasingInInnerLoops.h: To optimize simple assignments, the HLSL compiler frontend
  //      may record a variable as aliasing another. Sometimes the alias information gets garbled
  //      so we work around this issue by breaking the aliasing chain in inner loops.
  
  #include "compiler/translator/tree_ops/d3d/BreakVariableAliasingInInnerLoops.h"
  
  #include "compiler/translator/Compiler.h"
  #include "compiler/translator/tree_util/IntermNode_util.h"
  #include "compiler/translator/tree_util/IntermTraverse.h"
  
  // A HLSL compiler developer gave us more details on the root cause and the workaround needed:
  //     The root problem is that if the HLSL compiler is applying aliasing information even on
  //     incomplete simulations (in this case, a single pass). The bug is triggered by an assignment
  //     that comes from a series of assignments, possibly with swizzled or ternary operators with
  //     known conditionals, where the source is before the loop.
  //     So, a workaround is to add a +0 term to variables the first time they are assigned to in
  //     an inner loop (if they are declared in an outside scope, otherwise there is no need).
  //     This will break the aliasing chain.
  
  // For simplicity here we add a +0 to any assignment that is in at least two nested loops. Because
  // the bug only shows up with swizzles, and ternary assignment, whole array or whole structure
  // assignment don't need a workaround.
  
  namespace sh
  {
  
  namespace
  {
  
  class AliasingBreaker : public TIntermTraverser
  {
    public:
      AliasingBreaker() : TIntermTraverser(true, false, true) {}
  
    protected:
      bool visitBinary(Visit visit, TIntermBinary *binary) override
      {
          if (visit != PreVisit)
          {
              return false;
          }
  
          if (mLoopLevel < 2 || !binary->isAssignment())
          {
              return true;
          }
  
          TIntermTyped *B = binary->getRight();
          TType type      = B->getType();
  
          if (!type.isScalar() && !type.isVector() && !type.isMatrix())
          {
              return true;
          }
  
          if (type.isArray() || IsSampler(type.getBasicType()))
          {
              return true;
          }
  
          // We have a scalar / vector / matrix assignment with loop depth 2.
          // Transform it from
          //    A = B
          // to
          //    A = (B + typeof<B>(0));
  
          TIntermBinary *bPlusZero = new TIntermBinary(EOpAdd, B, CreateZeroNode(type));
          bPlusZero->setLine(B->getLine());
  
          binary->replaceChildNode(B, bPlusZero);
  
          return true;
      }
  
      bool visitLoop(Visit visit, TIntermLoop *loop) override
      {
          if (visit == PreVisit)
          {
              mLoopLevel++;
          }
          else
          {
              ASSERT(mLoopLevel > 0);
              mLoopLevel--;
          }
  
          return true;
      }
  
    private:
      int mLoopLevel = 0;
  };
  
  }  // anonymous namespace
  
  bool BreakVariableAliasingInInnerLoops(TCompiler *compiler, TIntermNode *root)
  {
      AliasingBreaker breaker;
      root->traverse(&breaker);
  
      return compiler->validateAST(root);
  }
  
  }  // namespace sh
  

Download