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Support constexpr pointers (#6907)

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This moves the LValue path code from macros.cpp to constant.cpp, so that
it can be called from `MapAPValueToConstant`. TODO messages are updated
accordingly to avoid referring to macros. Added a constexpr pointer test
to `constexpr.carbon` to show the result of this change.
This commit is contained in:
Nicholas Bishop
2026-03-16 19:19:20 +00:00
committed by GitHub
parent c006013e0c
commit 943cd41924
7 changed files with 185 additions and 123 deletions
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toolchain/check/cpp/constant.cpp
+127 -6
View File
@@ -5,20 +5,105 @@
#include "toolchain/check/cpp/constant.h"
#include "toolchain/check/cpp/import.h"
#include "toolchain/check/cpp/type_mapping.h"
#include "toolchain/check/eval.h"
#include "toolchain/check/member_access.h"
#include "toolchain/check/type.h"
#include "toolchain/check/type_completion.h"
#include "toolchain/diagnostics/format_providers.h"
namespace Carbon::Check {
static auto MapLValueToConstant(Context& context, SemIR::LocId loc_id,
const clang::APValue& ap_value,
clang::QualType type) -> SemIR::ConstantId {
CARBON_CHECK(ap_value.isLValue(), "not an LValue");
const auto* value_decl =
ap_value.getLValueBase().get<const clang::ValueDecl*>();
if (!ap_value.hasLValuePath()) {
context.TODO(loc_id, "lvalue has no path");
return SemIR::ErrorInst::ConstantId;
}
if (ap_value.isLValueOnePastTheEnd()) {
context.TODO(loc_id, "one-past-the-end lvalue");
return SemIR::ErrorInst::ConstantId;
}
auto key = SemIR::ClangDeclKey::ForNonFunctionDecl(
// TODO: can this const_cast be avoided?
const_cast<clang::ValueDecl*>(value_decl));
auto inst_id = ImportCppDecl(context, loc_id, key);
if (ap_value.getLValuePath().size() == 0) {
return context.constant_values().Get(inst_id);
}
// Import the base type so that its fields can be accessed.
auto var_storage = context.insts().GetAs<SemIR::VarStorage>(inst_id);
// TODO: currently an error isn't reachable here because incomplete
// array types can't be imported. Once that changes, switch to
// `RequireCompleteType` and handle the error.
CompleteTypeOrCheckFail(context, var_storage.type_id);
clang::QualType qual_type = ap_value.getLValueBase().getType();
for (const auto& entry : ap_value.getLValuePath()) {
if (qual_type->isArrayType()) {
context.TODO(loc_id, "lvalue path contains an array type");
} else {
const auto* decl =
cast<clang::Decl>(entry.getAsBaseOrMember().getPointer());
const auto* field_decl = dyn_cast<clang::FieldDecl>(decl);
if (!field_decl) {
context.TODO(loc_id, "lvalue path contains a base class subobject");
return SemIR::ErrorInst::ConstantId;
}
auto field_inst_id =
ImportCppDecl(context, loc_id,
SemIR::ClangDeclKey::ForNonFunctionDecl(
const_cast<clang::FieldDecl*>(field_decl)));
if (field_inst_id == SemIR::ErrorInst::InstId) {
context.TODO(loc_id,
"unsupported field in lvalue path: " +
ap_value.getAsString(context.ast_context(), type));
return SemIR::ErrorInst::ConstantId;
}
const SemIR::FieldDecl& field_decl_inst =
context.insts().GetAs<SemIR::FieldDecl>(field_inst_id);
qual_type = field_decl->getType();
inst_id = PerformMemberAccess(context, loc_id, inst_id,
field_decl_inst.name_id);
}
}
return context.constant_values().Get(inst_id);
}
auto MapAPValueToConstant(Context& context, SemIR::LocId loc_id,
const clang::APValue& ap_value, clang::QualType type)
-> SemIR::ConstantId {
const clang::APValue& ap_value, clang::QualType type,
bool is_lvalue) -> SemIR::ConstantId {
SemIR::TypeId type_id = ImportCppType(context, loc_id, type).type_id;
if (!type_id.has_value()) {
return SemIR::ConstantId::NotConstant;
}
if (ap_value.isInt()) {
if (is_lvalue) {
return MapLValueToConstant(context, loc_id, ap_value, type);
} else if (type->isPointerType()) {
auto const_id = MapLValueToConstant(context, loc_id, ap_value, type);
auto inst_id = AddInst<SemIR::AddrOf>(
context, loc_id,
{.type_id = type_id,
.lvalue_id = context.constant_values().GetInstId(const_id)});
return context.constant_values().Get(inst_id);
} else if (ap_value.isInt()) {
if (type->isBooleanType()) {
auto value = SemIR::BoolValue::From(!ap_value.getInt().isZero());
return TryEvalInst(
@@ -36,10 +121,45 @@ auto MapAPValueToConstant(Context& context, SemIR::LocId loc_id,
context, SemIR::FloatValue{.type_id = type_id, .float_id = float_id});
} else {
// TODO: support other types.
return SemIR::ConstantId::NotConstant;
context.TODO(loc_id, "unsupported conversion to constant from APValue " +
ap_value.getAsString(context.ast_context(), type));
return SemIR::ErrorInst::ConstantId;
}
}
static auto MapAPValueToConstantForConstexpr(Context& context,
SemIR::LocId loc_id,
const clang::APValue& ap_value,
clang::QualType type)
-> SemIR::ConstantId {
bool is_lvalue = false;
if (type->isReferenceType()) {
is_lvalue = true;
type = type.getNonReferenceType();
}
return MapAPValueToConstant(context, loc_id, ap_value, type, is_lvalue);
}
auto EvalCppVarDecl(Context& context, SemIR::LocId loc_id,
const clang::VarDecl* var_decl, SemIR::TypeId type_id)
-> SemIR::ConstantId {
// If the C++ global is constant, map it to a Carbon constant.
if (var_decl->isUsableInConstantExpressions(context.ast_context())) {
if (const auto* ap_value = var_decl->getEvaluatedValue()) {
auto clang_type = MapToCppType(context, type_id);
if (clang_type.isNull()) {
context.TODO(loc_id, "failed to map C++ type to Carbon");
return SemIR::ErrorInst::ConstantId;
}
return MapAPValueToConstantForConstexpr(context, loc_id, *ap_value,
clang_type);
}
}
return SemIR::ConstantId::NotConstant;
}
static auto ConvertConstantToAPValue(Context& context,
SemIR::InstId const_inst_id,
clang::QualType param_type)
@@ -136,8 +256,9 @@ auto EvalCppCall(Context& context, SemIR::LocId loc_id,
function_decl->isConsteval());
return SemIR::ErrorInst::ConstantId;
}
return MapAPValueToConstant(context, loc_id, eval_result.Val,
function_decl->getCallResultType());
return MapAPValueToConstantForConstexpr(context, loc_id, eval_result.Val,
function_decl->getCallResultType());
}
} // namespace Carbon::Check
toolchain/check/cpp/constant.h
+6 -1
View File
@@ -13,7 +13,12 @@ namespace Carbon::Check {
// Converts an `APValue` to a Carbon `ConstantId`.
auto MapAPValueToConstant(Context& context, SemIR::LocId loc_id,
const clang::APValue& ap_value, clang::QualType type)
const clang::APValue& ap_value, clang::QualType type,
bool is_lvalue) -> SemIR::ConstantId;
// Attempt to evaluate a C++ constexpr variable as a Carbon constant.
auto EvalCppVarDecl(Context& context, SemIR::LocId loc_id,
const clang::VarDecl* var_decl, SemIR::TypeId type_id)
-> SemIR::ConstantId;
// Attempt to evaluate a call to a C++ constexpr/consteval function as a
toolchain/check/cpp/macros.cpp
+10 -82
View File
@@ -12,8 +12,6 @@
#include "toolchain/check/cpp/constant.h"
#include "toolchain/check/cpp/import.h"
#include "toolchain/check/literal.h"
#include "toolchain/check/member_access.h"
#include "toolchain/check/type_completion.h"
namespace Carbon::Check {
@@ -109,87 +107,17 @@ auto TryEvaluateMacro(Context& context, SemIR::LocId loc_id,
CARBON_FATAL("failed to evaluate macro as constant expression");
}
clang::APValue ap_value = evaluated_result.Val;
// TODO: Add support for other types.
if (result_expr->isGLValue()) {
const auto* value_decl =
ap_value.getLValueBase().get<const clang::ValueDecl*>();
if (!ap_value.hasLValuePath()) {
context.TODO(loc_id, "Macro expanded to lvalue with no path");
return SemIR::ErrorInst::InstId;
}
if (ap_value.isLValueOnePastTheEnd()) {
context.TODO(loc_id, "Macro expanded to a one-past-the-end lvalue");
return SemIR::ErrorInst::InstId;
}
auto key = SemIR::ClangDeclKey::ForNonFunctionDecl(
// TODO: can this const_cast be avoided?
const_cast<clang::ValueDecl*>(value_decl));
auto inst_id = ImportCppDecl(context, loc_id, key);
if (ap_value.getLValuePath().size() == 0) {
return inst_id;
}
// Import the base type so that its fields can be accessed.
auto var_storage = context.insts().GetAs<SemIR::VarStorage>(inst_id);
// TODO: currently an error isn't reachable here because incomplete
// array types can't be imported. Once that changes, switch to
// `RequireCompleteType` and handle the error.
CompleteTypeOrCheckFail(context, var_storage.type_id);
clang::QualType qual_type = ap_value.getLValueBase().getType();
for (const auto& entry : ap_value.getLValuePath()) {
if (qual_type->isArrayType()) {
context.TODO(loc_id, "Macro expanded to array type");
} else {
const auto* decl =
cast<clang::Decl>(entry.getAsBaseOrMember().getPointer());
const auto* field_decl = dyn_cast<clang::FieldDecl>(decl);
if (!field_decl) {
context.TODO(loc_id, "Macro expanded to a base class subobject");
return SemIR::ErrorInst::InstId;
}
auto field_inst_id =
ImportCppDecl(context, loc_id,
SemIR::ClangDeclKey::ForNonFunctionDecl(
const_cast<clang::FieldDecl*>(field_decl)));
if (field_inst_id == SemIR::ErrorInst::InstId) {
context.TODO(loc_id,
"Unsupported field in macro expansion: " +
ap_value.getAsString(context.ast_context(),
result_expr->getType()));
return SemIR::ErrorInst::InstId;
}
const SemIR::FieldDecl& field_decl_inst =
context.insts().GetAs<SemIR::FieldDecl>(field_inst_id);
qual_type = field_decl->getType();
inst_id = PerformMemberAccess(context, loc_id, inst_id,
field_decl_inst.name_id);
}
}
return inst_id;
} else {
auto const_id =
MapAPValueToConstant(context, loc_id, ap_value, result_expr->getType());
if (const_id == SemIR::ConstantId::NotConstant) {
context.TODO(loc_id,
"Unsupported: macro evaluated to a constant of type: " +
result_expr->getType().getAsString());
return SemIR::ErrorInst::InstId;
}
return context.constant_values().GetInstId(const_id);
auto const_id = MapAPValueToConstant(context, loc_id, evaluated_result.Val,
result_expr->getType(),
/*is_lvalue=*/result_expr->isGLValue());
if (const_id == SemIR::ConstantId::NotConstant) {
context.TODO(loc_id,
"Unsupported: macro evaluated to a constant of type: " +
result_expr->getType().getAsString());
return SemIR::ErrorInst::InstId;
}
return context.constant_values().GetInstId(const_id);
}
} // namespace Carbon::Check
toolchain/check/eval_inst.cpp
+4 -14
View File
@@ -128,20 +128,10 @@ auto EvalConstantInst(Context& /*context*/, SemIR::ValueBinding /*inst*/)
auto EvalConstantInst(Context& context, SemIR::InstId inst_id,
SemIR::AcquireValue inst) -> ConstantEvalResult {
if (const auto* var_decl = GetAsClangVarDecl(context, inst.value_id)) {
// If the C++ global is constant, map it to a Carbon constant.
if (var_decl->isUsableInConstantExpressions(context.ast_context())) {
if (const auto* ap_value = var_decl->getEvaluatedValue()) {
auto clang_type = MapToCppType(context, inst.type_id);
if (clang_type.isNull()) {
return ConstantEvalResult::TODO;
}
auto const_id = MapAPValueToConstant(context, SemIR::LocId(inst_id),
*ap_value, clang_type);
if (const_id.has_value() && const_id.is_constant()) {
return ConstantEvalResult::Existing(const_id);
}
}
auto const_id =
EvalCppVarDecl(context, SemIR::LocId(inst_id), var_decl, inst.type_id);
if (const_id.has_value() && const_id.is_constant()) {
return ConstantEvalResult::Existing(const_id);
}
return ConstantEvalResult::NotConstant;
toolchain/check/testdata/interop/cpp/constexpr.carbon
Vendored
+13
View File
@@ -46,6 +46,19 @@ class C(V:! f32) {}
fn F() -> C(Cpp.flt);
let x: C(123.5) = F();
// --- pointer.carbon
library "[[@TEST_NAME]]";
import Cpp inline '''
int i = 123;
constexpr int* _Nonnull ptr = &i;
''';
class C(V:! i32*) {}
fn F() -> C(Cpp.ptr);
let x: C(&Cpp.i) = F();
// --- function.carbon
library "[[@TEST_NAME]]";
toolchain/check/testdata/interop/cpp/macros.carbon
Vendored
+22 -19
View File
@@ -868,7 +868,20 @@ fn F() {
//@dump-sem-ir-end
}
// --- fail_todo_assign_through_pointer.carbon
// --- assign_pointer.carbon
library "[[@TEST_NAME]]";
import Cpp inline '''
int *p;
#define q p
''';
var n: i32;
fn F() {
Cpp.q = &n;
}
// --- assign_through_pointer.carbon
library "[[@TEST_NAME]]";
import Cpp inline '''
@@ -877,18 +890,7 @@ int v = 1;
''';
fn F() {
// CHECK:STDERR: fail_todo_assign_through_pointer.carbon:[[@LINE+11]]:5: error: semantics TODO: `Unsupported: macro evaluated to a constant of type: int *` [SemanticsTodo]
// CHECK:STDERR: (*Cpp.m) = 2;
// CHECK:STDERR: ^~~~~
// CHECK:STDERR: fail_todo_assign_through_pointer.carbon:[[@LINE+8]]:5: note: in `Cpp` name lookup for `m` [InCppNameLookup]
// CHECK:STDERR: (*Cpp.m) = 2;
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_assign_through_pointer.carbon:[[@LINE+4]]:5: error: member name `m` not found in `Cpp` [MemberNameNotFoundInInstScope]
// CHECK:STDERR: (*Cpp.m) = 2;
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
(*Cpp.m) = 2;
*Cpp.m.Get() = 2;
}
// --- assign_subobject.carbon
@@ -932,7 +934,7 @@ fn F() {
// CHECK:STDERR: Cpp.m = 2;
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_assign_array.carbon:[[@LINE+11]]:3: error: semantics TODO: `Unsupported field in macro expansion: &s.arr[1]` [SemanticsTodo]
// CHECK:STDERR: fail_todo_assign_array.carbon:[[@LINE+11]]:3: error: semantics TODO: `unsupported field in lvalue path: &s.arr[1]` [SemanticsTodo]
// CHECK:STDERR: Cpp.m = 2;
// CHECK:STDERR: ^~~~~
// CHECK:STDERR: fail_todo_assign_array.carbon:[[@LINE+8]]:3: note: in `Cpp` name lookup for `m` [InCppNameLookup]
@@ -959,7 +961,7 @@ struct B : A {} b;
''';
fn F() {
// CHECK:STDERR: fail_todo_assign_base_class_member.carbon:[[@LINE+11]]:3: error: semantics TODO: `Macro expanded to a base class subobject` [SemanticsTodo]
// CHECK:STDERR: fail_todo_assign_base_class_member.carbon:[[@LINE+11]]:3: error: semantics TODO: `lvalue path contains a base class subobject` [SemanticsTodo]
// CHECK:STDERR: Cpp.m = 2;
// CHECK:STDERR: ^~~~~
// CHECK:STDERR: fail_todo_assign_base_class_member.carbon:[[@LINE+8]]:3: note: in `Cpp` name lookup for `m` [InCppNameLookup]
@@ -2073,12 +2075,12 @@ fn F() {
// CHECK:STDOUT: --- assign_subobject.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %int_32: Core.IntLiteral = int_value 32 [concrete]
// CHECK:STDOUT: %i32: type = class_type @Int, @Int(%int_32) [concrete]
// CHECK:STDOUT: %A: type = class_type @A [concrete]
// CHECK:STDOUT: %pattern_type.9de: type = pattern_type %A [concrete]
// CHECK:STDOUT: %B: type = class_type @B [concrete]
// CHECK:STDOUT: %A.elem: type = unbound_element_type %A, %B [concrete]
// CHECK:STDOUT: %int_32: Core.IntLiteral = int_value 32 [concrete]
// CHECK:STDOUT: %i32: type = class_type @Int, @Int(%int_32) [concrete]
// CHECK:STDOUT: %B.elem: type = unbound_element_type %B, %i32 [concrete]
// CHECK:STDOUT: %.1b7: ref %B = class_element_access imports.%a.var, element0 [concrete]
// CHECK:STDOUT: %.59e: ref %i32 = class_element_access %.1b7, element0 [concrete]
@@ -2101,7 +2103,7 @@ fn F() {
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
// CHECK:STDOUT: %Cpp: <namespace> = namespace file.%Cpp.import_cpp, [concrete] {
// CHECK:STDOUT: .m = @F.%.loc17_6.2
// CHECK:STDOUT: .m = constants.%.59e
// CHECK:STDOUT: import Cpp//...
// CHECK:STDOUT: }
// CHECK:STDOUT: %a.patt: %pattern_type.9de = ref_binding_pattern a [concrete]
@@ -2114,11 +2116,12 @@ fn F() {
// CHECK:STDOUT: fn @F() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %Cpp.ref: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %b.ref: %A.elem = name_ref b, @A.%.1 [concrete = @A.%.1]
// CHECK:STDOUT: %.loc17_6.1: ref %B = class_element_access imports.%a.var, element0 [concrete = constants.%.1b7]
// CHECK:STDOUT: %c.ref: %B.elem = name_ref c, @B.%.1 [concrete = @B.%.1]
// CHECK:STDOUT: %.loc17_6.2: ref %i32 = class_element_access %.loc17_6.1, element0 [concrete = constants.%.59e]
// CHECK:STDOUT: %m.ref: ref %i32 = name_ref m, %.loc17_6.2 [concrete = constants.%.59e]
// CHECK:STDOUT: %m.ref: ref %i32 = name_ref m, constants.%.59e [concrete = constants.%.59e]
// CHECK:STDOUT: %int_2: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
// CHECK:STDOUT: %impl.elem0: %.545 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
// CHECK:STDOUT: %bound_method.loc17_9.1: <bound method> = bound_method %int_2, %impl.elem0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound]
toolchain/check/testdata/interop/cpp/var/global.carbon
Vendored
+3 -1
View File
@@ -83,6 +83,7 @@ fn MyF() {
// CHECK:STDOUT: %const: type = const_type %ptr.d9e [concrete]
// CHECK:STDOUT: %pattern_type.8ca: type = pattern_type %const [concrete]
// CHECK:STDOUT: %global_ref.var: ref %ptr.d9e = var imports.%global_ref.var_patt [concrete]
// CHECK:STDOUT: %addr: %ptr.d9e = addr_of imports.%global.var [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
@@ -168,7 +169,8 @@ fn MyF() {
// CHECK:STDOUT: }
// CHECK:STDOUT: %.loc9_37.1: ref %ptr.d9e = as_compatible %global_ref.ref [concrete = constants.%global_ref.var]
// CHECK:STDOUT: %.loc9_37.2: ref %ptr.d9e = converted %global_ref.ref, %.loc9_37.1 [concrete = constants.%global_ref.var]
// CHECK:STDOUT: %.loc9_37.3: %ptr.d9e = acquire_value %.loc9_37.2
// CHECK:STDOUT: %addr: %ptr.d9e = addr_of imports.%global.var [concrete = constants.%addr]
// CHECK:STDOUT: %.loc9_37.3: %ptr.d9e = acquire_value %.loc9_37.2 [concrete = constants.%addr]
// CHECK:STDOUT: %local_ref: %ptr.d9e = value_binding local_ref, %.loc9_37.3
// CHECK:STDOUT: return
// CHECK:STDOUT: }