Add an effects(releasenone) function effects attribute

A ``@effects(releasenone)`` function might read/write global state but does not
perform a release.

Author: aschwaighofer

include/swift/AST/AttrKind.h

@@ -73,6 +73,7 @@ enum class InlineKind : uint8_t {
 enum class EffectsKind : uint8_t {
   ReadNone,
   ReadOnly,
+  ReleaseNone,
   ReadWrite,
   Unspecified
 };

include/swift/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t VERSION_MINOR = 401; // Last change: ValueOwnership
+const uint16_t VERSION_MINOR = 402; // Last change: effects(releasenone)
 
 using DeclIDField = BCFixed<31>;
 

lib/AST/Attr.cpp

@@ -601,7 +601,9 @@ StringRef DeclAttribute::getAttrName() const {
         return "effects(readnone)";
       case EffectsKind::ReadOnly:
         return "effects(readonly)";
-      case EffectsKind::ReadWrite:
+      case EffectsKind::ReleaseNone:
+        return "effects(releasenone)";
+     case EffectsKind::ReadWrite:
         return "effects(readwrite)";
       case EffectsKind::Unspecified:
         return "effects(unspecified)";

lib/Parse/ParseDecl.cpp

@@ -583,6 +583,8 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
       kind = EffectsKind::ReadNone;
     else if (Tok.getText() == "readwrite")
       kind = EffectsKind::ReadWrite;
+    else if (Tok.getText() == "releasenone")
+      kind = EffectsKind::ReleaseNone;
     else {
       diagnose(Loc, diag::effects_attribute_unknown_option,
                Tok.getText(), AttrName);

lib/ParseSIL/ParseSIL.cpp

@@ -936,6 +936,8 @@ static bool parseDeclSILOptional(bool *isTransparent,
       *MRK = EffectsKind::ReadOnly;
     else if (MRK && SP.P.Tok.getText() == "readwrite")
       *MRK = EffectsKind::ReadWrite;
+    else if (MRK && SP.P.Tok.getText() == "releasenone")
+      *MRK = EffectsKind::ReleaseNone;
     else if (Semantics && SP.P.Tok.getText() == "_semantics") {
       SP.P.consumeToken(tok::identifier);
       if (SP.P.Tok.getKind() != tok::string_literal) {

lib/SIL/SILPrinter.cpp

@@ -2307,8 +2307,10 @@ void SILFunction::print(SILPrintContext &PrintCtx) const {
     OS << "[readonly] ";
   else if (getEffectsKind() == EffectsKind::ReadNone)
       OS << "[readnone] ";
-  if (getEffectsKind() == EffectsKind::ReadWrite)
+  else if (getEffectsKind() == EffectsKind::ReadWrite)
     OS << "[readwrite] ";
+  else if (getEffectsKind() == EffectsKind::ReleaseNone)
+    OS << "[releasenone] ";
 
   for (auto &Attr : getSemanticsAttrs())
     OS << "[_semantics \"" << Attr << "\"] ";

lib/SILOptimizer/Analysis/SideEffectAnalysis.cpp

@@ -159,6 +159,11 @@ bool SideEffectAnalysis::getDefinedEffects(FunctionEffects &Effects,
     return true;
   }
   switch (F->getEffectsKind()) {
+    case EffectsKind::ReleaseNone:
+      Effects.GlobalEffects.Reads = true;
+      Effects.GlobalEffects.Writes = true;
+      Effects.GlobalEffects.Releases = false;
+      return true;
     case EffectsKind::ReadNone:
       return true;
     case EffectsKind::ReadOnly:

lib/SILOptimizer/SILCombiner/SILCombinerApplyVisitors.cpp

@@ -1317,7 +1317,7 @@ SILInstruction *SILCombiner::visitApplyInst(ApplyInst *AI) {
 
   // Optimize readonly functions with no meaningful users.
   SILFunction *SF = AI->getReferencedFunction();
-  if (SF && SF->getEffectsKind() < EffectsKind::ReadWrite) {
+  if (SF && SF->getEffectsKind() < EffectsKind::ReleaseNone) {
     UserListTy Users;
     if (recursivelyCollectARCUsers(Users, AI)) {
       if (eraseApply(AI, Users))
@@ -1327,7 +1327,7 @@ SILInstruction *SILCombiner::visitApplyInst(ApplyInst *AI) {
   }
 
   if (SF) {
-    if (SF->getEffectsKind() < EffectsKind::ReadWrite) {
+    if (SF->getEffectsKind() < EffectsKind::ReleaseNone) {
       // Try to optimize string concatenation.
       if (auto I = optimizeConcatenationOfStringLiterals(AI)) {
         return I;
@@ -1450,7 +1450,7 @@ SILInstruction *SILCombiner::visitTryApplyInst(TryApplyInst *AI) {
 
   // Optimize readonly functions with no meaningful users.
   SILFunction *Fn = AI->getReferencedFunction();
-  if (Fn && Fn->getEffectsKind() < EffectsKind::ReadWrite) {
+  if (Fn && Fn->getEffectsKind() < EffectsKind::ReleaseNone) {
     UserListTy Users;
     if (isTryApplyResultNotUsed(Users, AI)) {
       SILBasicBlock *BB = AI->getParent();

lib/SILOptimizer/Utils/Local.cpp

@@ -693,8 +693,8 @@ bool StringConcatenationOptimizer::extractStringConcatOperands() {
   auto *FRILeftFun = FRILeft->getReferencedFunction();
   auto *FRIRightFun = FRIRight->getReferencedFunction();
 
-  if (FRILeftFun->getEffectsKind() >= EffectsKind::ReadWrite ||
-      FRIRightFun->getEffectsKind() >= EffectsKind::ReadWrite)
+  if (FRILeftFun->getEffectsKind() >= EffectsKind::ReleaseNone ||
+      FRIRightFun->getEffectsKind() >= EffectsKind::ReleaseNone)
     return false;
 
   if (!FRILeftFun->hasSemanticsAttrs() || !FRIRightFun->hasSemanticsAttrs())

lib/Serialization/SILFormat.h

@@ -289,7 +289,7 @@ namespace sil_block {
                      BCFixed<1>,  // global_init
                      BCFixed<2>,  // inlineStrategy
                      BCFixed<2>,  // optimizationMode
-                     BCFixed<2>,  // side effect info.
+                     BCFixed<3>,  // side effect info.
                      BCVBR<8>,    // number of specialize attributes
                      BCFixed<1>,  // has qualified ownership
                      BCFixed<1>,  // must be weakly referenced