[SILGen] Record local auxiliary decls when a parameter is emitted, and

emit those auxiliary decls inside the function body brace statement.

This generalizes the old code to work for parameters to any kind of
function (e.g. initializers).

Author: hborla

lib/SILGen/SILGenFunction.cpp

@@ -517,23 +517,6 @@ void SILGenFunction::emitFunction(FuncDecl *fd) {
       // original asyncHandler.
       !F.isAsync()) {
     emitAsyncHandler(fd);
-  } else if (llvm::any_of(*fd->getParameters(),
-                          [](ParamDecl *p){ return p->hasAttachedPropertyWrapper(); })) {
-    // If any parameters have property wrappers, emit the local auxiliary
-    // variables before emitting the function body.
-    LexicalScope BraceScope(*this, CleanupLocation(fd));
-    for (auto *param : *fd->getParameters()) {
-      param->visitAuxiliaryDecls([&](VarDecl *auxiliaryVar) {
-        SILLocation WrapperLoc(auxiliaryVar);
-        WrapperLoc.markAsPrologue();
-        if (auto *patternBinding = auxiliaryVar->getParentPatternBinding())
-          visitPatternBindingDecl(patternBinding);
-
-        visit(auxiliaryVar);
-      });
-    }
-
-    emitStmt(fd->getTypecheckedBody());
   } else {
     emitStmt(fd->getTypecheckedBody());
   }
@@ -606,11 +589,6 @@ void SILGenFunction::emitClosure(AbstractClosureExpr *ace) {
   emitProlog(captureInfo, ace->getParameters(), /*selfParam=*/nullptr,
              ace, resultIfaceTy, ace->isBodyThrowing(), ace->getLoc());
   prepareEpilog(true, ace->isBodyThrowing(), CleanupLocation(ace));
-  for (auto *param : *ace->getParameters()) {
-    param->visitAuxiliaryDecls([&](VarDecl *auxiliaryVar) {
-      visit(auxiliaryVar);
-    });
-  }
 
   if (auto *ce = dyn_cast<ClosureExpr>(ace)) {
     emitStmt(ce->getBody());

lib/SILGen/SILGenFunction.h

@@ -376,6 +376,10 @@ class LLVM_LIBRARY_VISIBILITY SILGenFunction
   /// a local variable.
   llvm::DenseMap<ValueDecl*, VarLoc> VarLocs;
 
+  /// The local auxiliary declarations for the parameters of this function that
+  /// need to be emitted inside the next brace statement.
+  llvm::SmallVector<VarDecl *, 2> LocalAuxiliaryDecls;
+
   // Context information for tracking an `async let` child task.
   struct AsyncLetChildTask {
     SILValue asyncLet; // RawPointer to the async let state

lib/SILGen/SILGenProlog.cpp

@@ -244,6 +244,10 @@ struct ArgumentInitHelper {
   }
 
   void emitParam(ParamDecl *PD) {
+    PD->visitAuxiliaryDecls([&](VarDecl *localVar) {
+      SGF.LocalAuxiliaryDecls.push_back(localVar);
+    });
+
     if (PD->hasExternalPropertyWrapper()) {
       PD = cast<ParamDecl>(PD->getPropertyWrapperBackingProperty());
     }

lib/SILGen/SILGenStmt.cpp

@@ -282,7 +282,19 @@ void StmtEmitter::visitBraceStmt(BraceStmt *S) {
   const unsigned ThrowStmtType    = 3;
   const unsigned UnknownStmtType  = 4;
   unsigned StmtType = UnknownStmtType;
-  
+
+  // Emit local auxiliary declarations.
+  if (!SGF.LocalAuxiliaryDecls.empty()) {
+    for (auto *var : SGF.LocalAuxiliaryDecls) {
+      if (auto *patternBinding = var->getParentPatternBinding())
+        SGF.visit(patternBinding);
+
+      SGF.visit(var);
+    }
+
+    SGF.LocalAuxiliaryDecls.clear();
+  }
+
   for (auto &ESD : S->getElements()) {
 
     if (auto D = ESD.dyn_cast<Decl*>())