IRGen: Add another lldb resilience hack

When accessing global variables defined in the REPL, lldb does not consult
debug info, so it does not see that the DW_OP_deref was emitted.

So instead, set a special bit on globals defined in the REPL which bypasses
resilience for them altogether.

Part of the fix <rdar://problem/39722386>.

Author: slavapestov

include/swift/AST/Decl.h

@@ -328,7 +328,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     StorageKind : 4
   );
 
-  SWIFT_INLINE_BITFIELD(VarDecl, AbstractStorageDecl, 1+4+1+1+1,
+  SWIFT_INLINE_BITFIELD(VarDecl, AbstractStorageDecl, 1+4+1+1+1+1,
     /// \brief Whether this property is a type property (currently unfortunately
     /// called 'static').
     IsStatic : 1,
@@ -347,7 +347,11 @@ class alignas(1 << DeclAlignInBits) Decl {
 
     /// \brief Whether this is a property used in expressions in the debugger.
     /// It is up to the debugger to instruct SIL how to access this variable.
-    IsDebuggerVar : 1
+    IsDebuggerVar : 1,
+
+    /// \brief Whether this is a property defined in the debugger's REPL.
+    /// FIXME: Remove this once LLDB has proper support for resilience.
+    IsREPLVar : 1
   );
 
   SWIFT_INLINE_BITFIELD(ParamDecl, VarDecl, 1 + NumDefaultArgumentKindBits,
@@ -4576,6 +4580,7 @@ class VarDecl : public AbstractStorageDecl {
     Bits.VarDecl.Specifier = static_cast<unsigned>(Sp);
     Bits.VarDecl.IsCaptureList = IsCaptureList;
     Bits.VarDecl.IsDebuggerVar = false;
+    Bits.VarDecl.IsREPLVar = false;
     Bits.VarDecl.HasNonPatternBindingInit = false;
     setType(Ty);
   }
@@ -4762,6 +4767,13 @@ class VarDecl : public AbstractStorageDecl {
   void setDebuggerVar(bool IsDebuggerVar) {
     Bits.VarDecl.IsDebuggerVar = IsDebuggerVar;
   }
+  
+  /// Is this a special debugger REPL variable?
+  /// FIXME: Remove this once LLDB has proper support for resilience.
+  bool isREPLVar() const { return Bits.VarDecl.IsREPLVar; }
+  void setREPLVar(bool IsREPLVar) {
+    Bits.VarDecl.IsREPLVar = IsREPLVar;
+  }
 
   /// Return the Objective-C runtime name for this property.
   Identifier getObjCPropertyName() const;

lib/IRGen/GenDecl.cpp

@@ -2123,6 +2123,12 @@ Address IRGenModule::getAddrOfSILGlobalVariable(SILGlobalVariable *var,
   bool inFixedBuffer = false;
   bool indirectForDebugInfo = false;
 
+  // FIXME: Remove this once LLDB has proper support for resilience.
+  bool isREPLVar = false;
+  if (auto *decl = var->getDecl())
+    if (decl->isREPLVar())
+      isREPLVar = true;
+
   if (var->isInitializedObject()) {
     assert(ti.isFixedSize(expansion));
     StructLayout *Layout = StaticObjectLayouts[var].get();
@@ -2142,7 +2148,7 @@ Address IRGenModule::getAddrOfSILGlobalVariable(SILGlobalVariable *var,
     fixedSize = Layout->getSize();
     fixedAlignment = Layout->getAlignment();
     assert(fixedAlignment >= TargetInfo.HeapObjectAlignment);
-  } else if (ti.isFixedSize(expansion)) {
+  } else if (isREPLVar || ti.isFixedSize(expansion)) {
     // Allocate static storage.
     auto &fixedTI = cast<FixedTypeInfo>(ti);
     storageType = fixedTI.getStorageType();

lib/IRGen/IRGenSIL.cpp

@@ -1857,9 +1857,15 @@ void IRGenSILFunction::visitAllocGlobalInst(AllocGlobalInst *i) {
 
   auto expansion = IGM.getResilienceExpansionForLayout(var);
 
+  // FIXME: Remove this once LLDB has proper support for resilience.
+  bool isREPLVar = false;
+  if (auto *decl = var->getDecl())
+    if (decl->isREPLVar())
+      isREPLVar = true;
+
   // If the global is fixed-size in all resilience domains that can see it,
   // we allocated storage for it statically, and there's nothing to do.
-  if (ti.isFixedSize(expansion))
+  if (isREPLVar || ti.isFixedSize(expansion))
     return;
 
   // Otherwise, the static storage for the global consists of a fixed-size
@@ -1887,9 +1893,15 @@ void IRGenSILFunction::visitGlobalAddrInst(GlobalAddrInst *i) {
   Address addr = IGM.getAddrOfSILGlobalVariable(var, ti,
                                                 NotForDefinition);
 
+  // FIXME: Remove this once LLDB has proper support for resilience.
+  bool isREPLVar = false;
+  if (auto *decl = var->getDecl())
+    if (decl->isREPLVar())
+      isREPLVar = true;
+
   // If the global is fixed-size in all resilience domains that can see it,
   // we allocated storage for it statically, and there's nothing to do.
-  if (ti.isFixedSize(expansion)) {
+  if (isREPLVar || ti.isFixedSize(expansion)) {
     setLoweredAddress(i, addr);
     return;
   }