RewriteInterpolants.h

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//

// Copyright 2023 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.

//

#ifndef COMPILER_TRANSLATOR_TREEOPS_MSL_REWRITEINTERPOLANTS_H_

#define COMPILER_TRANSLATOR_TREEOPS_MSL_REWRITEINTERPOLANTS_H_

#include "compiler/translator/msl/DriverUniformMetal.h"

#include "compiler/translator/tree_util/IntermTraverse.h"

namespace sh

// This transformation handles multisample interpolation semantics.

//

//  1. Types of all fragment inputs used with interpolation functions are adjusted with

//     an interpolant flag because MSL treats them as a separate type (Section 2.18).

//

//  2. Offset origin (0, 0) is in the pixel's upper-left corner in Metal but

//     in the pixel's center in OpenGL ES. Additionally, the Y direction may

//     be flipped depending on the bound FBO.

//

//  3. When a fragment input is used with any interpolation function, its regular usages

//     are wrapped with explicit interpolation functions based on the input's qualifier.

//

//  4. The outUsesSampleInterpolation variable is set to true if any fragment input

//     uses sample qualifier. This flag limits gl_SampleMaskIn built-in variable to

//     the current sample because Metal's [[sample_mask]] always contains all bits.

//

//  5. The outUsesSampleInterpolant variable is set to true if any fragment input that

//     has sample qualifier and is used as an argument to an interpolation function is

//     also used directly. This requires implicitly defining gl_SampleID.

[[nodiscard]] bool RewriteInterpolants(TCompiler &compiler,

                                       TIntermBlock &root,

                                       TSymbolTable &symbolTable,

                                       const DriverUniformMetal *driverUniforms,

                                       bool *outUsesSampleInterpolation,

                                       bool *outUsesSampleInterpolant);

}  // namespace sh

#endif  // COMPILER_TRANSLATOR_TREEOPS_MSL_REWRITEINTERPOLANTS_H_