src/tint/utils/internal_limits.h

// Copyright 2024 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef SRC_TINT_UTILS_INTERNAL_LIMITS_H_
#define SRC_TINT_UTILS_INTERNAL_LIMITS_H_

#include <cstddef>
#include <cstdint>

// Contains constants for internal limits used within Tint. These limits are not specified in the
// WGSL spec, but are practical heuristics to limit certain operations that are known to cause
// memory or runtime issues, i.e. creation of arrays with 100k elements that cause IR binary
// decoding to take pathologically long times to run.

namespace tint::internal_limits {

// Limits the nest depth of composite types
constexpr size_t kMaxNestDepthOfCompositeType = 255;

// Limits the number of elements in an array type
constexpr int64_t kMaxArrayElementCount = 64LL * 1024;

// The max subgroup size supported. Used in validation.
constexpr int64_t kMaxSubgroupSize = 128;

// A quad (fragment) is composed of four invocations.
constexpr int64_t kQuadSize = 4;

// A @size attribute maximum size
constexpr int64_t kMaxStructMemberPadding = 10LL * 1024 * 1024;

// Limits the size of result types instructions that will be transiently created, i.e. not buffers.
// Specifically prevents unreasonably large initializers when printing in the backend. The related
// minimum maximums from the spec are 8kB, so this 64kB limit should be significantly beyond what a
// user can expect to work.
constexpr int64_t kMaxTemporaryStorageSize = 64LL * 1024;

// Limits the combined size of all private variables in the shader.
// The WGSL spec has a min-max for a single variable of 8KB, so this 8MB limit is well above that.
constexpr int64_t kMaxCombinedPrivateVariableSize = 8LL * 1024 * 1024;

// The maximum number of locations allowed for shader IO.
// This hard limit is derived from spirv-val (kMaxLocations in
// https://github.com/KhronosGroup/SPIRV-Tools/blob/main/source/val/validate_interfaces.cpp).
// Device-specific API limits will likely be much lower, but will be caught by Dawn before
// shader module generation.
constexpr uint32_t kMaxLocations = 4096;

}  // namespace tint::internal_limits

#endif  // SRC_TINT_UTILS_INTERNAL_LIMITS_H_