kc3-lang/angle/src/compiler/translator/wgsl/WGSLProgramPrelude.cpp

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• Hash : fecb8ead
  Author :
  Date : 2025-09-04T12:27:48
  

  WGSL: implement inc/dec with generated functions
  
  Implements inc/dec with generated WGSL functions that take pointers
  and perform a post/pre inc/decrement. This works with scalars, vectors,
  and matrices, both float and int.
  
  WGSL supports inc/dec only on integer types, and only as statements
  (not as expressions). https://www.w3.org/TR/WGSL/#increment-decrement.
  The regular ++ and -- are used in this specific case.
  
  The WGSL outputter records usage of increment/decrement and produces
  a call to the correct function. A new class is introduced to keep the
  record of which types need generated inc/dec WGSL functions.
  
  Bug: angleproject:42267100
  Change-Id: I0e70760ba5bd00f978e216f958216ae3137a146e
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6935269
  Commit-Queue: Matthew Denton <mpdenton@chromium.org>
  Reviewed-by: Geoff Lang <geofflang@chromium.org>
  

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• src/compiler/translator/wgsl/WGSLProgramPrelude.cpp

• //
  // Copyright 2025 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.
  //
  
  #include "compiler/translator/wgsl/WGSLProgramPrelude.h"
  #include "common/log_utils.h"
  #include "compiler/translator/BaseTypes.h"
  #include "compiler/translator/ImmutableString.h"
  #include "compiler/translator/util.h"
  #include "compiler/translator/wgsl/Utils.h"
  
  namespace sh
  {
  
  namespace
  {
  constexpr ImmutableString kEndParanthesis = ImmutableString(")");
  
  void EmitConstructorList(TInfoSinkBase &sink, const TType &type, ImmutableString scalar)
  {
      ASSERT(!type.isArray());
      ASSERT(!type.getStruct());
  
      sink << "(";
      size_t numScalars = 1;
      if (type.isMatrix())
      {
          numScalars = type.getCols() * type.getRows();
      }
      for (size_t i = 0; i < numScalars; i++)
      {
          if (i != 0)
          {
              sink << ", ";
          }
          sink << scalar;
      }
      sink << ")";
  }
  }  // namespace
  
  WGSLWrapperFunction WGSLProgramPrelude::preIncrement(const TType &incrementedType)
  {
      mPreIncrementedTypes.insert(incrementedType);
      switch (incrementedType.getQualifier())
      {
          case EvqTemporary:
          // NOTE: As of Sept 2025, parameters are immutable in WGSL (and are handled by an AST pass
          // that copies parameters to temporaries). Include these here in case parameters become
          // mutable in the future.
          case EvqParamIn:
          case EvqParamOut:
          case EvqParamInOut:
              return {ImmutableString("preIncFunc(&"), kEndParanthesis};
          default:
              // EvqGlobal and various other shader outputs/builtins are all globals.
              return {ImmutableString("preIncPriv(&"), kEndParanthesis};
      }
  }
  
  WGSLWrapperFunction WGSLProgramPrelude::preDecrement(const TType &decrementedType)
  {
      mPreDecrementedTypes.insert(decrementedType);
      switch (decrementedType.getQualifier())
      {
          case EvqTemporary:
          // NOTE: As of Sept 2025, parameters are immutable in WGSL (and are handled by an AST pass
          // that copies parameters to temporaries). Include these here in case parameters become
          // mutable in the future.
          case EvqParamIn:
          case EvqParamOut:
          case EvqParamInOut:
              return {ImmutableString("preDecFunc(&"), kEndParanthesis};
          default:
              // EvqGlobal and various other shader outputs/builtins are all globals.
              return {ImmutableString("preDecPriv(&"), kEndParanthesis};
      }
  }
  
  WGSLWrapperFunction WGSLProgramPrelude::postIncrement(const TType &incrementedType)
  {
      mPostIncrementedTypes.insert(incrementedType);
      switch (incrementedType.getQualifier())
      {
          case EvqTemporary:
          // NOTE: As of Sept 2025, parameters are immutable in WGSL (and are handled by an AST pass
          // that copies parameters to temporaries). Include these here in case parameters become
          // mutable in the future.
          case EvqParamIn:
          case EvqParamOut:
          case EvqParamInOut:
              return {ImmutableString("postIncFunc(&"), kEndParanthesis};
          default:
              // EvqGlobal and various other shader outputs/builtins are all globals.
              return {ImmutableString("postIncPriv(&"), kEndParanthesis};
      }
  }
  
  WGSLWrapperFunction WGSLProgramPrelude::postDecrement(const TType &decrementedType)
  {
      mPostDecrementedTypes.insert(decrementedType);
      switch (decrementedType.getQualifier())
      {
          case EvqTemporary:
          // NOTE: As of Sept 2025, parameters are immutable in WGSL (and are handled by an AST pass
          // that copies parameters to temporaries). Include these here in case parameters become
          // mutable in the future.
          case EvqParamIn:
          case EvqParamOut:
          case EvqParamInOut:
              return {ImmutableString("postDecFunc(&"), kEndParanthesis};
          default:
              // EvqGlobal and various other shader outputs/builtins are all globals.
              return {ImmutableString("postDecPriv(&"), kEndParanthesis};
      }
  }
  
  void WGSLProgramPrelude::outputPrelude(TInfoSinkBase &sink)
  {
      auto genPreIncOrDec = [&](ImmutableString addressSpace, const TType &type, ImmutableString op,
                                ImmutableString funcName) {
          TStringStream typeStr;
          WriteWgslType(typeStr, type, {});
  
          sink << "fn " << funcName << "(x : ptr<" << addressSpace << ", " << typeStr.str()
               << ">) -> " << typeStr.str() << " {\n";
          sink << "  (*x) " << op << " " << typeStr.str();
          EmitConstructorList(sink, type, ImmutableString("1"));
          sink << ";\n";
          sink << "  return *x;\n";
          sink << "}\n";
      };
      for (const TType &type : mPreIncrementedTypes)
      {
  
          // NOTE: it's easiest just to generate increments and decrements functions for variables
          // that live in either the function-local scope or the module-local scope. TType holds a
          // qualifier, but its operator== and operator< ignore the qualifier. We could keep track of
          // the qualifiers used but that's overkill.
          genPreIncOrDec(ImmutableString("private"), type, ImmutableString("+="),
                         ImmutableString("preIncPriv"));
          genPreIncOrDec(ImmutableString("function"), type, ImmutableString("+="),
                         ImmutableString("preIncFunc"));
      }
      for (const TType &type : mPreDecrementedTypes)
      {
  
          // NOTE: it's easiest just to generate increments and decrements functions for variables
          // that live in either the function-local scope or the module-local scope. TType holds a
          // qualifier, but its operator== and operator< ignore the qualifier. We could keep track of
          // the qualifiers used but that's overkill.
          genPreIncOrDec(ImmutableString("private"), type, ImmutableString("-="),
                         ImmutableString("preDecPriv"));
          genPreIncOrDec(ImmutableString("function"), type, ImmutableString("-="),
                         ImmutableString("preDecFunc"));
      }
  
      auto genPostIncOrDec = [&](ImmutableString addressSpace, const TType &type, ImmutableString op,
                                 ImmutableString funcName) {
          TStringStream typeStr;
          WriteWgslType(typeStr, type, {});
  
          sink << "fn " << funcName << "(x : ptr<" << addressSpace << ", " << typeStr.str()
               << ">) -> " << typeStr.str() << " {\n";
          sink << "  var old = *x;\n";
          sink << "  (*x) " << op << " " << typeStr.str();
          EmitConstructorList(sink, type, ImmutableString("1"));
          sink << ";\n";
          sink << "  return old;\n";
          sink << "}\n";
      };
      for (const TType &type : mPostIncrementedTypes)
      {
          // NOTE: it's easiest just to generate increments and decrements functions for variables
          // that live in either the function-local scope or the module-local scope. TType holds a
          // qualifier, but its operator== and operator< ignore the qualifier. We could keep track of
          // the qualifiers used but that's overkill.
          genPostIncOrDec(ImmutableString("private"), type, ImmutableString("+="),
                          ImmutableString("postIncPriv"));
          genPostIncOrDec(ImmutableString("function"), type, ImmutableString("+="),
                          ImmutableString("postIncFunc"));
      }
      for (const TType &type : mPostDecrementedTypes)
      {
          // NOTE: it's easiest just to generate increments and decrements functions for variables
          // that live in either the function-local scope or the module-local scope. TType holds a
          // qualifier, but its operator== and operator< ignore the qualifier. We could keep track of
          // the qualifiers used but that's overkill.
          genPostIncOrDec(ImmutableString("private"), type, ImmutableString("-="),
                          ImmutableString("postDecPriv"));
          genPostIncOrDec(ImmutableString("function"), type, ImmutableString("-="),
                          ImmutableString("postDecFunc"));
      }
  }
  
  }  // namespace sh
  

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