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// Copyright 2023 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "src/tint/lang/wgsl/reader/parser/classify_template_args.h"
#include <vector>
#include "src/tint/utils/containers/vector.h"
#include "src/tint/utils/ice/ice.h"
namespace tint::wgsl::reader {
namespace {
/// If the token at index @p idx is a '>>', '>=' or '>>=', then the token is split into two, with
/// the first being '>', otherwise MaybeSplit() will be a no-op.
/// @param tokens the vector of tokens
/// @param idx the index of the token to (maybe) split
void MaybeSplit(std::vector<Token>& tokens, size_t idx) {
Token* token = &tokens[idx];
switch (token->type()) {
case Token::Type::kShiftRight: // '>>'
TINT_ASSERT(token[1].type() == Token::Type::kPlaceholder);
token[0].SetType(Token::Type::kGreaterThan);
token[1].SetType(Token::Type::kGreaterThan);
break;
case Token::Type::kGreaterThanEqual: // '>='
TINT_ASSERT(token[1].type() == Token::Type::kPlaceholder);
token[0].SetType(Token::Type::kGreaterThan);
token[1].SetType(Token::Type::kEqual);
break;
case Token::Type::kShiftRightEqual: // '>>='
TINT_ASSERT(token[1].type() == Token::Type::kPlaceholder);
token[0].SetType(Token::Type::kGreaterThan);
token[1].SetType(Token::Type::kGreaterThanEqual);
break;
default:
break;
}
}
} // namespace
void ClassifyTemplateArguments(std::vector<Token>& tokens) {
const size_t count = tokens.size();
// The current expression nesting depth.
// Each '(', '[' increments the depth.
// Each ')', ']' decrements the depth.
uint64_t expr_depth = 0;
// A stack of '<' tokens.
// Used to pair '<' and '>' tokens at the same expression depth.
struct StackEntry {
Token* token; // A pointer to the opening '<' token
uint64_t expr_depth; // The value of 'expr_depth' for the opening '<'
};
Vector<StackEntry, 16> stack;
for (size_t i = 0; i < count - 1; i++) {
switch (tokens[i].type()) {
case Token::Type::kIdentifier:
case Token::Type::kVar:
case Token::Type::kBitcast: {
auto& next = tokens[i + 1];
if (next.type() == Token::Type::kLessThan) {
// ident '<'
// Push this '<' to the stack, along with the current nesting expr_depth.
stack.Push(StackEntry{&tokens[i + 1], expr_depth});
i++; // Skip the '<'
}
break;
}
case Token::Type::kGreaterThan: // '>'
case Token::Type::kShiftRight: // '>>'
case Token::Type::kGreaterThanEqual: // '>='
case Token::Type::kShiftRightEqual: // '>>='
if (!stack.IsEmpty() && stack.Back().expr_depth == expr_depth) {
// '<' and '>' at same expr_depth, and no terminating tokens in-between.
// Consider both as a template argument list.
MaybeSplit(tokens, i);
stack.Pop().token->SetType(Token::Type::kTemplateArgsLeft);
tokens[i].SetType(Token::Type::kTemplateArgsRight);
}
break;
case Token::Type::kParenLeft: // '('
case Token::Type::kBracketLeft: // '['
// Entering a nested expression
expr_depth++;
break;
case Token::Type::kParenRight: // ')'
case Token::Type::kBracketRight: // ']'
// Exiting a nested expression
// Pop the stack until we return to the current expression expr_depth
while (!stack.IsEmpty() && stack.Back().expr_depth == expr_depth) {
stack.Pop();
}
if (expr_depth > 0) {
expr_depth--;
}
break;
case Token::Type::kSemicolon: // ';'
case Token::Type::kBraceLeft: // '{'
case Token::Type::kEqual: // '='
case Token::Type::kColon: // ':'
// Expression terminating tokens. No opening template list can hold these tokens, so
// clear the stack and expression depth.
expr_depth = 0;
stack.Clear();
break;
case Token::Type::kOrOr: // '||'
case Token::Type::kAndAnd: // '&&'
// Treat 'a < b || c > d' as a logical binary operator of two comparison operators
// instead of a single template argument 'b||c'.
// Use parentheses around 'b||c' to parse as a template argument list.
while (!stack.IsEmpty() && stack.Back().expr_depth == expr_depth) {
stack.Pop();
}
break;
default:
break;
}
}
}
} // namespace tint::wgsl::reader