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Jan 11, 2021
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[cxx-interop] Inline constexpr vars. #35311

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4 changes: 2 additions & 2 deletions lib/AST/ASTScopeCreation.cpp
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Expand Up @@ -209,8 +209,8 @@ void ASTScope::
}

void ASTScope::expandFunctionBody(AbstractFunctionDecl *AFD) {
auto *const SF = AFD->getParentSourceFile();
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I think the problem here is that we've never actually had a C++ function with a body before. And because there's no source file associated with a C++ decl context, it makes sense that this might be null.

SF->getScope().expandFunctionBodyImpl(AFD);
if (auto *const SF = AFD->getParentSourceFile())
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This should be const auto * rather than auto * const which makes the pointer const. While the pointer is nice to make const, it is not as valuable as the value itself being marked const.

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Unfortunately, that doesn't work because getScope is not a const member (and can't be because it lazily creates the scope). So, I'm going to leave this as-is.

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I think that this case deserves a comment to explain why/when we expect a source to be missing.

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Good point. Fixed in a follow up here: #35364.

SF->getScope().expandFunctionBodyImpl(AFD);
}

void ASTScope::expandFunctionBodyImpl(AbstractFunctionDecl *AFD) {
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46 changes: 46 additions & 0 deletions lib/ClangImporter/ImportDecl.cpp
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Expand Up @@ -4094,6 +4094,47 @@ namespace {
return nullptr;
}

AccessorDecl *tryCreateConstexprAccessor(const clang::VarDecl *clangVar,
VarDecl *swiftVar) {
assert(clangVar->isConstexpr());
clangVar->evaluateValue();
auto evaluated = clangVar->getEvaluatedValue();
if (!evaluated)
return nullptr;

// If we have a constexpr var with an evaluated value, try to create an
// accessor for it. If we can remove all references to the global (which
// we should be able to do for constexprs) then we can remove the global
// entirely.
auto accessor = AccessorDecl::create(
Impl.SwiftContext, SourceLoc(), SourceLoc(), AccessorKind::Get,
swiftVar, SourceLoc(), StaticSpellingKind::KeywordStatic,
/*throws=*/false, SourceLoc(), /*genericParams*/ nullptr,
ParameterList::createEmpty(Impl.SwiftContext), swiftVar->getType(),
swiftVar->getDeclContext());
Expr *value = nullptr;
// TODO: add non-numeric types.
if (evaluated->isInt()) {
value = IntegerLiteralExpr::createFromUnsigned(
Impl.SwiftContext,
static_cast<unsigned>(
clangVar->getEvaluatedValue()->getInt().getZExtValue()));
} else if (evaluated->isFloat()) {
auto floatStr = evaluated->getAsString(Impl.getClangASTContext(),
clang::QualType());
auto floatIdent = Impl.SwiftContext.getIdentifier(floatStr);
value = new (Impl.SwiftContext)
FloatLiteralExpr(floatIdent.str(), SourceLoc());
}
if (!value)
return nullptr;
auto returnStmt = new (Impl.SwiftContext) ReturnStmt(SourceLoc(), value);
auto body = BraceStmt::create(Impl.SwiftContext, SourceLoc(),
{returnStmt}, SourceLoc());
accessor->setBodyParsed(body);
return accessor;
}

Decl *VisitVarDecl(const clang::VarDecl *decl) {
// Variables are imported as... variables.
Optional<ImportedName> correctSwiftName;
Expand Down Expand Up @@ -4161,6 +4202,11 @@ namespace {
if (correctSwiftName)
markAsVariant(result, *correctSwiftName);

// For constexpr vars, we can create an accessor with a numeric literal.
if (decl->isConstexpr())
if (auto acc = tryCreateConstexprAccessor(decl, result))
result->setAccessors(SourceLoc(), {acc}, SourceLoc());

return result;
}

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6 changes: 6 additions & 0 deletions test/Interop/Cxx/static/Inputs/static-member-var.h
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Expand Up @@ -26,9 +26,15 @@ class WithConstStaticMember {
const static int definedOutOfLine;
};

constexpr float getFloatValue() { return 42; }
constexpr float getIntValue(int arg) { return 40 + arg; }

class WithConstexprStaticMember {
public:
constexpr static int definedInline = 139;
constexpr static int definedInlineWithArg = getIntValue(2);
constexpr static float definedInlineFloat = 139;
constexpr static float definedInlineFromMethod = getFloatValue();
};

class ClassA {
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52 changes: 39 additions & 13 deletions test/Interop/Cxx/static/static-member-var-irgen.swift
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Expand Up @@ -10,14 +10,12 @@
// CHECK: @{{_ZN21WithConstStaticMember7definedE|"\?defined@WithConstStaticMember@@2HB"}} = {{available_externally|linkonce_odr}} {{(dso_local )?}}constant i32 48, {{(comdat, )?}}align 4
// CHECK: @{{_ZN21WithConstStaticMember16definedOutOfLineE|"\?definedOutOfLine@WithConstStaticMember@@2HB"}} = external {{(dso_local )?}}constant i32, align 4

//TODO: This test uses only values of static const members, so it does not need
//to depend on external definitions. However, our code generation pattern loads
//the value dynamically. Instead, we should inline known constants. That would
//allow Swift code to even read the value of WithIncompleteStaticMember::notDefined.
// NOTE: we allow both available_externally and linkonce_odr as there are
// differences in between MSVC and itanium model semantics where the constexpr
// value is emitted into COMDAT.
// CHECK: @{{_ZN25WithConstexprStaticMember13definedInlineE|"\?definedInline@WithConstexprStaticMember@@2HB"}} = {{available_externally|linkonce_odr}} {{(dso_local )?}}constant i32 139, {{(comdat, )?}}align 4
// Make sure we remove constexpr globals after all uses have been inlined.
// CHECK-NOT: _ZN25WithConstexprStaticMember13definedInlineE
// CHECK-NOT: ?definedInline@WithConstexprStaticMember@@2HB
// CHECK-NOT: @_ZN25WithConstexprStaticMember20definedInlineWithArgE
// CHECK-NOT: @_ZN25WithConstexprStaticMember18definedInlineFloatE
// CHECK-NOT: @_ZN25WithConstexprStaticMember23definedInlineFromMethodE

import StaticMemberVar

Expand Down Expand Up @@ -73,10 +71,38 @@ public func readDefinedOutOfLineConstMember() -> CInt {
// CHECK: [[VALUE:%.*]] = load i32, i32* getelementptr inbounds (%Ts5Int32V, %Ts5Int32V* bitcast (i32* @{{_ZN21WithConstStaticMember16definedOutOfLineE|"\?definedOutOfLine@WithConstStaticMember@@2HB"}} to %Ts5Int32V*), i32 0, i32 0), align 4
// CHECK: ret i32 [[VALUE]]

public func readConstexprStaticMember() -> CInt {
return WithConstexprStaticMember.definedInline
public func readConstexprStaticIntMembers() {
let x = WithConstexprStaticMember.definedInline
let y = WithConstexprStaticMember.definedInlineWithArg
}

// CHECK: define {{(protected |dllexport )?}}swiftcc i32 @"$s4main25readConstexprStaticMembers5Int32VyF"() #0
// CHECK: [[VALUE:%.*]] = load i32, i32* getelementptr inbounds (%Ts5Int32V, %Ts5Int32V* bitcast (i32* @{{_ZN25WithConstexprStaticMember13definedInlineE|"\?definedInline@WithConstexprStaticMember@@2HB"}} to %Ts5Int32V*), i32 0, i32 0), align 4
// CHECK: ret i32 [[VALUE]]
// CHECK-LABEL: define {{(protected |dllexport )?}}swiftcc void @"$s4main29readConstexprStaticIntMembersyyF"()
// CHECK: call swiftcc i32 @"$sSo25WithConstexprStaticMemberV13definedInlines5Int32VvgZ"()
// CHECK: call swiftcc i32 @"$sSo25WithConstexprStaticMemberV013definedInlineA3Args5Int32VvgZ"()
// CHECK: ret void

// CHECK-LABEL: define linkonce_odr {{.*}}swiftcc i32 @"$sSo25WithConstexprStaticMemberV13definedInlines5Int32VvgZ"()
// CHECK-NEXT: entry
// CHECK-NEXT: ret i32 139

// CHECK-LABEL: define linkonce_odr {{.*}}swiftcc i32 @"$sSo25WithConstexprStaticMemberV013definedInlineA3Args5Int32VvgZ"()
// CHECK-NEXT: entry
// CHECK-NEXT: ret i32 42

public func readConstexprStaticFloatMembers() {
let x = WithConstexprStaticMember.definedInlineFloat
let y = WithConstexprStaticMember.definedInlineFromMethod
}

// CHECK-LABEL: define {{(protected |dllexport )?}}swiftcc void @"$s4main31readConstexprStaticFloatMembersyyF"()
// CHECK: call swiftcc float @"$sSo25WithConstexprStaticMemberV18definedInlineFloatSfvgZ"()
// CHECK: call swiftcc float @"$sSo25WithConstexprStaticMemberV23definedInlineFromMethodSfvgZ"()
// CHECK: ret void

// CHECK-LABEL: define linkonce_odr {{.*}}swiftcc float @"$sSo25WithConstexprStaticMemberV18definedInlineFloatSfvgZ"()
// CHECK-NEXT: entry
// CHECK-NEXT: ret float 1.390000e+02

// CHECK-LABEL: define linkonce_odr {{.*}}swiftcc float @"$sSo25WithConstexprStaticMemberV23definedInlineFromMethodSfvgZ"()
// CHECK-NEXT: entry
// CHECK-NEXT: ret float 4.200000e+01
24 changes: 13 additions & 11 deletions test/Interop/Cxx/static/static-member-var-silgen.swift
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Expand Up @@ -8,8 +8,6 @@
// CHECK: sil_global public_external [let] @{{_ZN21WithConstStaticMember7definedE|\?defined@WithConstStaticMember@@2HB}} : $Int32
// CHECK: // clang name: WithConstStaticMember::definedOutOfLine
// CHECK: sil_global public_external [let] @{{_ZN21WithConstStaticMember16definedOutOfLineE|\?definedOutOfLine@WithConstStaticMember@@2HB}} : $Int32
// CHECK: // clang name: WithConstexprStaticMember::definedInline
// CHECK: sil_global public_external [let] @{{_ZN25WithConstexprStaticMember13definedInlineE|\?definedInline@WithConstexprStaticMember@@2HB}} : $Int32

import StaticMemberVar

Expand Down Expand Up @@ -70,16 +68,20 @@ func readDefinedOutOfLineConstMember() -> CInt {
return WithConstStaticMember.definedOutOfLine
}

// CHECK: sil hidden @$s4main31readDefinedOutOfLineConstMembers5Int32VyF : $@convention(thin) () -> Int32
// CHECK: [[ADDR:%.*]] = global_addr @{{_ZN21WithConstStaticMember16definedOutOfLineE|\?definedOutOfLine@WithConstStaticMember@@2HB}} : $*Int32
// CHECK: [[VALUE:%.*]] = load [[ADDR]] : $*Int32
// CHECK: return [[VALUE]] : $Int32
// CHECK: sil hidden @$s4main25readConstexprStaticMembers5Int32VyF : $@convention(thin) () -> Int32
// CHECK: [[META:%.*]] = metatype $@thin WithConstexprStaticMember.Type
// CHECK: [[ACC:%.*]] = function_ref @$sSo25WithConstexprStaticMemberV13definedInlines5Int32VvgZ : $@convention(method) (@thin WithConstexprStaticMember.Type) -> Int32
// CHECK: [[OUT:%.*]] = apply [[ACC]]([[META]]) : $@convention(method) (@thin WithConstexprStaticMember.Type) -> Int32
// CHECK: return [[OUT]] : $Int32
// CHECK-LABEL: end sil function '$s4main25readConstexprStaticMembers5Int32VyF'

// Make sure we also generate the accessor with a numeric literal.
// CHECK-LABEL: sil shared [serializable] @$sSo25WithConstexprStaticMemberV13definedInlines5Int32VvgZ : $@convention(method) (@thin WithConstexprStaticMember.Type) -> Int32
// CHECK: [[IL:%.*]] = integer_literal $Builtin.Int32, 139
// CHECK: [[OUT:%.*]] = struct $Int32 ([[IL]] : $Builtin.Int32)
// CHECK: return [[OUT]] : $Int32
// CHECK-LABEL: end sil function '$sSo25WithConstexprStaticMemberV13definedInlines5Int32VvgZ'

func readConstexprStaticMember() -> CInt {
return WithConstexprStaticMember.definedInline
}

// CHECK: sil hidden @$s4main25readConstexprStaticMembers5Int32VyF : $@convention(thin) () -> Int32
// CHECK: [[ADDR:%.*]] = global_addr @{{_ZN25WithConstexprStaticMember13definedInlineE|\?definedInline@WithConstexprStaticMember@@2HB}} : $*Int32
// CHECK: [[VALUE:%.*]] = load [[ADDR]] : $*Int32
// CHECK: return [[VALUE]] : $Int32
5 changes: 4 additions & 1 deletion test/Interop/Cxx/static/static-var-irgen.swift
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Expand Up @@ -8,13 +8,16 @@ public func initStaticVars() -> CInt {
+ staticConstexprNonTrivial.val
}

// Constexpr vars should be inlined and removed.
// CHECK-NOT: ?staticConstexpr
// CHECK-NOT: _ZL15staticConstexpr

// CHECK: @{{_ZL9staticVar|staticVar}} = internal global i32 2, align 4
// CHECK: @{{_ZL13staticVarInit|staticVarInit}} = internal global i32 0, align 4
// CHECK: @{{_ZL19staticVarInlineInit|staticVarInlineInit}} = internal global i32 0, align 4
// CHECK: @{{_ZL11staticConst|staticConst}} = internal constant i32 4, align 4
// CHECK: @{{_ZL15staticConstInit|staticConstInit}} = internal global i32 0, align 4
// CHECK: @{{_ZL21staticConstInlineInit|staticConstInlineInit}} = internal global i32 0, align 4
// CHECK: @{{_ZL15staticConstexpr|staticConstexpr}} = internal constant i32 32, align 4
// CHECK: @{{_ZL16staticNonTrivial|staticNonTrivial}} = internal global %class.NonTrivial zeroinitializer, align 4
// CHECK: @{{_ZL21staticConstNonTrivial|staticConstNonTrivial}} = internal global %class.NonTrivial zeroinitializer, align 4
// CHECK: @{{_ZL25staticConstexprNonTrivial|staticConstexprNonTrivial}} = internal constant %class.NonTrivial { i32 8192 }, align 4
Expand Down
5 changes: 3 additions & 2 deletions test/Interop/Cxx/static/static-var-silgen.swift
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Expand Up @@ -8,6 +8,9 @@ func initStaticVars() -> CInt {
+ staticConstexprNonTrivial.val
}

// Constexpr globals should be inlined and removed.
// CHECK-NOT: sil_global public_external [let] @staticConstexpr : $Int32

// CHECK: // clang name: staticVar
// CHECK: sil_global public_external @staticVar : $Int32
// CHECK: // clang name: staticVarInit
Expand All @@ -20,8 +23,6 @@ func initStaticVars() -> CInt {
// CHECK: sil_global public_external [let] @staticConstInit : $Int32
// CHECK: // clang name: staticConstInlineInit
// CHECK: sil_global public_external [let] @staticConstInlineInit : $Int32
// CHECK: // clang name: staticConstexpr
// CHECK: sil_global public_external [let] @staticConstexpr : $Int32
// CHECK: // clang name: staticNonTrivial
// CHECK: sil_global public_external @staticNonTrivial : $NonTrivial
// CHECK: // clang name: staticConstNonTrivial
Expand Down