src/compiler/translator/VersionGLSL.cpp

//
// Copyright (c) 2002-2012 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/VersionGLSL.h"

static const int GLSL_VERSION_110 = 110;
static const int GLSL_VERSION_120 = 120;

// We need to scan for the following:
// 1. "invariant" keyword: This can occur in both - vertex and fragment shaders
//    but only at the global scope.
// 2. "gl_PointCoord" built-in variable: This can only occur in fragment shader
//    but inside any scope.
// 3. Call to a matrix constructor with another matrix as argument.
//    (These constructors were reserved in GLSL version 1.10.)
// 4. Arrays as "out" function parameters.
//    GLSL spec section 6.1.1: "When calling a function, expressions that do
//    not evaluate to l-values cannot be passed to parameters declared as
//    out or inout."
//    GLSL 1.1 section 5.8: "Other binary or unary expressions,
//    non-dereferenced arrays, function names, swizzles with repeated fields,
//    and constants cannot be l-values."
//    GLSL 1.2 relaxed the restriction on arrays, section 5.8: "Variables that
//    are built-in types, entire structures or arrays... are all l-values."
//
// TODO(alokp): The following two cases of invariant decalaration get lost
// during parsing - they do not get carried over to the intermediate tree.
// Handle these cases:
// 1. When a pragma is used to force all output variables to be invariant:
//    - #pragma STDGL invariant(all)
// 2. When a previously decalared or built-in variable is marked invariant:
//    - invariant gl_Position;
//    - varying vec3 color; invariant color;
//
TVersionGLSL::TVersionGLSL(sh::GLenum type)
    : mVersion(GLSL_VERSION_110)
{
}

void TVersionGLSL::visitSymbol(TIntermSymbol *node)
{
    if (node->getSymbol() == "gl_PointCoord")
        updateVersion(GLSL_VERSION_120);
}

bool TVersionGLSL::visitAggregate(Visit, TIntermAggregate *node)
{
    bool visitChildren = true;

    switch (node->getOp())
    {
      case EOpSequence:
        // We need to visit sequence children to get to global or inner scope.
        visitChildren = true;
        break;
      case EOpDeclaration:
        {
            const TIntermSequence &sequence = *(node->getSequence());
            TQualifier qualifier = sequence.front()->getAsTyped()->getQualifier();
            if ((qualifier == EvqInvariantVaryingIn) ||
                (qualifier == EvqInvariantVaryingOut))
            {
                updateVersion(GLSL_VERSION_120);
            }
            break;
        }
      case EOpParameters:
        {
            const TIntermSequence &params = *(node->getSequence());
            for (TIntermSequence::const_iterator iter = params.begin();
                 iter != params.end(); ++iter)
            {
                const TIntermTyped *param = (*iter)->getAsTyped();
                if (param->isArray())
                {
                    TQualifier qualifier = param->getQualifier();
                    if ((qualifier == EvqOut) || (qualifier ==  EvqInOut))
                    {
                        updateVersion(GLSL_VERSION_120);
                        break;
                    }
                }
            }
            // Fully processed. No need to visit children.
            visitChildren = false;
            break;
        }
      case EOpConstructMat2:
      case EOpConstructMat3:
      case EOpConstructMat4:
        {
            const TIntermSequence &sequence = *(node->getSequence());
            if (sequence.size() == 1)
            {
                TIntermTyped *typed = sequence.front()->getAsTyped();
                if (typed && typed->isMatrix())
                {
                    updateVersion(GLSL_VERSION_120);
                }
            }
            break;
        }
      default:
        break;
    }

    return visitChildren;
}

void TVersionGLSL::updateVersion(int version)
{
    mVersion = std::max(version, mVersion);
}