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https://github.com/carbon-language/carbon-lang.git
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Ivana Ivanovska
4ddff65e8e
Similarly to the enums, these are for the moment only available when referenced with a global scope “::”. Only integer constexpr are available for now. Part of #6303
115 lines
3.9 KiB
C++
115 lines
3.9 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "toolchain/check/cpp/macros.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/AST/Expr.h"
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#include "clang/Parse/Parser.h"
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#include "clang/Sema/Sema.h"
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#include "common/check.h"
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namespace Carbon::Check {
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auto TryEvaluateMacroToConstant(Context& context, SemIR::LocId loc_id,
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SemIR::NameId name_id,
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clang::MacroInfo* macro_info) -> clang::Expr* {
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auto name_str_opt = context.names().GetAsStringIfIdentifier(name_id);
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CARBON_CHECK(macro_info, "macro info missing");
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if (macro_info->getNumTokens() == 0) {
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context.TODO(loc_id, "Unsupported: macro with 0 replacement tokens");
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return nullptr;
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}
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clang::Sema& sema = context.clang_sema();
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clang::Preprocessor& preprocessor = sema.getPreprocessor();
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clang::Parser parser(preprocessor, sema, false);
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llvm::SmallVector<clang::Token> tokens(macro_info->tokens().begin(),
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macro_info->tokens().end());
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clang::Token current_token = parser.getCurToken();
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// Add eof token
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clang::Token eof;
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eof.startToken();
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eof.setKind(clang::tok::eof);
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eof.setLocation(current_token.getEndLoc());
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tokens.push_back(eof);
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tokens.push_back(current_token);
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preprocessor.EnterTokenStream(tokens, /*DisableMacroExpansion=*/false,
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/*IsReinject=*/false);
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parser.ConsumeAnyToken(true);
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// TODO: Identifiers are still only available if prefixed with "::" (e.g.
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// "#define M_Var ::myVar").
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parser.EnterScope(clang::Scope::DeclScope);
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clang::ExprResult result = parser.ParseConstantExpression();
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parser.ExitScope();
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clang::Expr* result_expr = result.get();
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bool success =
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!result.isInvalid() && parser.getCurToken().is(clang::tok::eof);
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if (!success) {
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parser.SkipUntil(clang::tok::eof);
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CARBON_DIAGNOSTIC(
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InCppMacroEvaluation, Error,
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"failed to parse macro Cpp.{0} to a valid constant expression",
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std::string);
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context.emitter().Emit(loc_id, InCppMacroEvaluation, (*name_str_opt).str());
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return nullptr;
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}
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result_expr = result_expr->IgnoreParenImpCasts();
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if (isa<clang::StringLiteral>(result_expr) ||
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isa<clang::CharacterLiteral>(result_expr) ||
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isa<clang::CXXNullPtrLiteralExpr>(result_expr)) {
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return result_expr;
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}
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clang::Expr::EvalResult evaluated_result;
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CARBON_CHECK(result_expr->EvaluateAsConstantExpr(evaluated_result,
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sema.getASTContext()));
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clang::APValue ap_value = evaluated_result.Val;
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// TODO: Add support for other types.
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if (ap_value.isLValue()) {
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if (!result_expr->EvaluateAsInt(evaluated_result, sema.getASTContext())) {
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context.TODO(loc_id,
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"Unsupported: macro evaluated to a non-integer LValue");
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return nullptr;
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}
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ap_value = evaluated_result.Val;
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}
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switch (ap_value.getKind()) {
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case clang::APValue::Int:
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if (result_expr->getType()->isBooleanType()) {
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return clang::CXXBoolLiteralExpr::Create(
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sema.getASTContext(), ap_value.getInt().getBoolValue(),
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result_expr->getType(), result_expr->getExprLoc());
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}
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return clang::IntegerLiteral::Create(
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sema.getASTContext(), ap_value.getInt(), result_expr->getType(),
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result_expr->getExprLoc());
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case clang::APValue::Float:
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return clang::FloatingLiteral::Create(
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sema.getASTContext(), ap_value.getFloat(),
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/*isExact=*/true, result_expr->getType(), result_expr->getExprLoc());
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default:
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context.TODO(loc_id,
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"Unsupported: macro evaluated to a constant of type: " +
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result_expr->getType().getAsString());
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return nullptr;
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}
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}
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} // namespace Carbon::Check
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