SIL: add the [perf_constraint] flag in SILFunction

Specifies that the optimizer and IRGen must not add runtime calls which are not in the function originally.
This attribute is set for functions with performance constraints or functions which are called from functions with performance.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/PassManager/Context.swift

@@ -620,6 +620,12 @@ extension Function {
     }
   }
 
+  func set(isPerformanceConstraint: Bool, _ context: FunctionPassContext) {
+    context.notifyEffectsChanged()
+    bridged.setIsPerformanceConstraint(isPerformanceConstraint)
+  }
+
+
   func fixStackNesting(_ context: FunctionPassContext) {
     context._bridged.fixStackNesting(bridged)
   }

docs/SIL.rst

@@ -1280,7 +1280,14 @@ The clang node owner.
 
 Specifies the performance constraints for the function, which defines which type
 of runtime functions are allowed to be called from the function.
+::
+
+  sil-function-attribute ::= '[perf_constraint]'
 
+Specifies that the optimizer and IRGen must not add runtime calls which are not
+in the function originally. This attribute is set for functions with performance
+constraints or functions which are called from functions with performance
+constraints.
 
 Argument Effects
 ````````````````

include/swift/SIL/SILBridging.h

@@ -542,6 +542,7 @@ struct BridgedFunction {
   BRIDGED_INLINE void setThunk(ThunkKind) const;
   BRIDGED_INLINE bool needsStackProtection() const;
   BRIDGED_INLINE void setNeedStackProtection(bool needSP) const;
+  BRIDGED_INLINE void setIsPerformanceConstraint(bool isPerfConstraint) const;
   BRIDGED_INLINE bool isResilientNominalDecl(BridgedNominalTypeDecl decl) const;
   BRIDGED_INLINE BridgedType getLoweredType(BridgedASTType type) const;
 

include/swift/SIL/SILBridgingImpl.h

@@ -672,6 +672,10 @@ void BridgedFunction::setNeedStackProtection(bool needSP) const {
   getFunction()->setNeedStackProtection(needSP);
 }
 
+void BridgedFunction::setIsPerformanceConstraint(bool isPerfConstraint) const {
+  getFunction()->setIsPerformanceConstraint(isPerfConstraint);
+}
+
 bool BridgedFunction::isResilientNominalDecl(BridgedNominalTypeDecl decl) const {
   return decl.unbridged()->isResilient(getFunction()->getModule().getSwiftModule(),
                                        getFunction()->getResilienceExpansion());

include/swift/SIL/SILFunction.h

@@ -445,6 +445,14 @@ class SILFunction
 
   unsigned HasResultDependsOnSelf : 1;
 
+  /// True, if this function or a caller (transitively) has a performance
+  /// constraint.
+  /// If true, optimizations must not introduce new runtime calls or metadata
+  /// creation, which are not there after SILGen.
+  /// Note that this flag is not serialized, because it's computed locally
+  /// within a module by the MandatoryOptimizations pass.
+  unsigned IsPerformanceConstraint : 1;
+
   static void
   validateSubclassScope(SubclassScope scope, IsThunk_t isThunk,
                         const GenericSpecializationInformation *genericInfo) {
@@ -1031,6 +1039,13 @@ class SILFunction
     perfConstraints = perfConstr;
   }
 
+  // see `IsPerformanceConstraint`
+  bool isPerformanceConstraint() const { return IsPerformanceConstraint; }
+
+  void setIsPerformanceConstraint(bool flag = true) {
+    IsPerformanceConstraint = flag;
+  }
+
   /// \returns True if the function is optimizable (i.e. not marked as no-opt),
   ///          or is raw SIL (so that the mandatory passes still run).
   bool shouldOptimize() const;

lib/SIL/IR/SILFunction.cpp

@@ -210,6 +210,7 @@ void SILFunction::init(
   this->UseStackForPackMetadata = DoUseStackForPackMetadata;
   this->HasUnsafeNonEscapableResult = false;
   this->HasResultDependsOnSelf = false;
+  this->IsPerformanceConstraint = false;
   this->stackProtection = false;
   this->Inlined = false;
   this->Zombie = false;

lib/SIL/IR/SILPrinter.cpp

@@ -3367,6 +3367,9 @@ void SILFunction::print(SILPrintContext &PrintCtx) const {
     case PerformanceConstraints::NoObjCBridging: OS << "[no_objc_bridging] "; break;
   }
 
+  if (isPerformanceConstraint())
+    OS << "[perf_constraint] ";
+
   if (getEffectsKind() == EffectsKind::ReadOnly)
     OS << "[readonly] ";
   else if (getEffectsKind() == EffectsKind::ReadNone)

lib/SIL/Parser/ParseSIL.cpp

@@ -675,6 +675,7 @@ static bool parseDeclSILOptional(
     SILFunction **usedAdHocRequirementWitness, Identifier *objCReplacementFor,
     SILFunction::Purpose *specialPurpose, Inline_t *inlineStrategy,
     OptimizationMode *optimizationMode, PerformanceConstraints *perfConstraints,
+    bool *isPerformanceConstraint,
     bool *markedAsUsed, StringRef *section, bool *isLet, bool *isWeakImported,
     bool *needStackProtection, AvailabilityContext *availability,
     bool *isWithoutActuallyEscapingThunk,
@@ -774,6 +775,8 @@ static bool parseDeclSILOptional(
       *perfConstraints = PerformanceConstraints::NoExistentials;
     else if (perfConstraints && SP.P.Tok.getText() == "no_objc_bridging")
       *perfConstraints = PerformanceConstraints::NoObjCBridging;
+    else if (isPerformanceConstraint && SP.P.Tok.getText() == "perf_constraint")
+      *isPerformanceConstraint = true;
     else if (markedAsUsed && SP.P.Tok.getText() == "used")
       *markedAsUsed = true;
     else if (section && SP.P.Tok.getText() == "section") {
@@ -7033,6 +7036,7 @@ bool SILParserState::parseDeclSIL(Parser &P) {
   Inline_t inlineStrategy = InlineDefault;
   OptimizationMode optimizationMode = OptimizationMode::NotSet;
   PerformanceConstraints perfConstr = PerformanceConstraints::None;
+  bool isPerformanceConstraint = false;
   bool markedAsUsed = false;
   StringRef section;
   SmallVector<std::string, 1> Semantics;
@@ -7050,7 +7054,8 @@ bool SILParserState::parseDeclSIL(Parser &P) {
           &useStackForPackMetadata, &hasUnsafeNonEscapableResult,
           &isExactSelfClass, &DynamicallyReplacedFunction,
           &AdHocWitnessFunction, &objCReplacementFor, &specialPurpose,
-          &inlineStrategy, &optimizationMode, &perfConstr, &markedAsUsed,
+          &inlineStrategy, &optimizationMode, &perfConstr,
+          &isPerformanceConstraint, &markedAsUsed,
           &section, nullptr, &isWeakImported, &needStackProtection,
           &availability, &isWithoutActuallyEscapingThunk, &Semantics,
           &SpecAttrs, &ClangDecl, &MRK, FunctionState, M) ||
@@ -7106,6 +7111,7 @@ bool SILParserState::parseDeclSIL(Parser &P) {
     FunctionState.F->setInlineStrategy(inlineStrategy);
     FunctionState.F->setOptimizationMode(optimizationMode);
     FunctionState.F->setPerfConstraints(perfConstr);
+    FunctionState.F->setIsPerformanceConstraint(isPerformanceConstraint);
     FunctionState.F->setEffectsKind(MRK);
 
     if (ClangDecl)
@@ -7302,6 +7308,7 @@ bool SILParserState::parseSILGlobal(Parser &P) {
       parseDeclSILOptional(nullptr, &isSerialized, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+                           nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, &isLet,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, State, M) ||
@@ -7356,7 +7363,7 @@ bool SILParserState::parseSILProperty(Parser &P) {
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                           nullptr, nullptr, SP, M))
+                           nullptr, nullptr, nullptr, SP, M))
     return true;
 
   ValueDecl *VD;
@@ -7426,7 +7433,7 @@ bool SILParserState::parseSILVTable(Parser &P) {
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                           nullptr, nullptr, VTableState, M))
+                           nullptr, nullptr, nullptr, VTableState, M))
     return true;
 
   // Parse the class name.
@@ -7537,7 +7544,7 @@ bool SILParserState::parseSILMoveOnlyDeinit(Parser &parser) {
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                           nullptr, nullptr, moveOnlyDeinitTableState, M))
+                           nullptr, nullptr, nullptr, moveOnlyDeinitTableState, M))
     return true;
 
   // Parse the class name.
@@ -8024,7 +8031,7 @@ bool SILParserState::parseSILWitnessTable(Parser &P) {
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
                            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                           nullptr, nullptr, WitnessState, M))
+                           nullptr, nullptr, nullptr, WitnessState, M))
     return true;
 
   // Parse the protocol conformance.