From 81a650ee87eb679e85a4ca3b1565c5fbd362a472 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Wed, 24 Oct 2018 23:28:28 +0000
Subject: Driver,CodeGen: introduce support for Swift CFString layout

Add a new driver level flag `-fcf-runtime-abi=` that allows one to specify the
runtime ABI for CoreFoundation.  This controls the language interoperability.
In particular, this is relevant for generating the CFConstantString classes
(primarily through the `__builtin___CFStringMakeConstantString` builtin) which
construct a reference to the "CFObject"'s `isa` field.  This type differs
between swift 4.1 and 4.2+.

Valid values for the new option include:
  - objc [default behaviour] - enable ObjectiveC interoperability
  - swift-4.1 - enable interoperability with swift 4.1
  - swift-4.2 - enable interoperability with swift 4.2
  - swift-5.0 - enable interoperability with swift 5.0
  - swift [alias] - target the latest swift ABI

Furthermore, swift 4.2+ changed the layout for the CFString when building
CoreFoundation *without* ObjectiveC interoperability.  In such a case, a field
was added to the CFObject base type changing it from: <{ const int*, int }> to
<{ uintptr_t, uintptr_t, uint64_t }>.

In swift 5.0, the CFString type will be further adjusted to change the length
from a uint32_t on everything but BE LP64 targets to uint64_t.

Note that the default behaviour for clang remains unchanged and the new layout
must be explicitly opted into via `-fcf-runtime-abi=swift*`.

llvm-svn: 345222
---
 clang/lib/CodeGen/CodeGenModule.cpp | 52 ++++++++++++++++++++++++++++++++-----
 1 file changed, 46 insertions(+), 6 deletions(-)

(limited to 'clang/lib/CodeGen/CodeGenModule.cpp')

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 9f4fbe9..c9f907b 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4124,12 +4124,37 @@ CodeGenModule::GetAddrOfConstantCFString(const StringLiteral *Literal) {
   const ASTContext &Context = getContext();
   const llvm::Triple &Triple = getTriple();
 
+  const auto CFRuntime = getLangOpts().CFRuntime;
+  const bool IsSwiftABI =
+      static_cast<unsigned>(CFRuntime) >=
+      static_cast<unsigned>(LangOptions::CoreFoundationABI::Swift);
+  const bool IsSwift4_1 = CFRuntime == LangOptions::CoreFoundationABI::Swift4_1;
+
   // If we don't already have it, get __CFConstantStringClassReference.
   if (!CFConstantStringClassRef) {
+    const char *CFConstantStringClassName = "__CFConstantStringClassReference";
     llvm::Type *Ty = getTypes().ConvertType(getContext().IntTy);
     Ty = llvm::ArrayType::get(Ty, 0);
-    llvm::Constant *C =
-        CreateRuntimeVariable(Ty, "__CFConstantStringClassReference");
+
+    switch (CFRuntime) {
+    default: break;
+    case LangOptions::CoreFoundationABI::Swift: LLVM_FALLTHROUGH;
+    case LangOptions::CoreFoundationABI::Swift5_0: LLVM_FALLTHROUGH;
+    case LangOptions::CoreFoundationABI::Swift4_2:
+      CFConstantStringClassName =
+          Triple.isOSDarwin() ? "$s15SwiftFoundation19_NSCFConstantStringCN"
+                              : "$s10Foundation19_NSCFConstantStringCN";
+      Ty = IntPtrTy;
+      break;
+    case LangOptions::CoreFoundationABI::Swift4_1:
+      CFConstantStringClassName =
+          Triple.isOSDarwin() ? "__T015SwiftFoundation19_NSCFConstantStringCN"
+                              : "__T010Foundation19_NSCFConstantStringCN";
+      Ty = IntPtrTy;
+      break;
+    }
+
+    llvm::Constant *C = CreateRuntimeVariable(Ty, CFConstantStringClassName);
 
     if (Triple.isOSBinFormatELF() || Triple.isOSBinFormatCOFF()) {
       llvm::GlobalValue *GV = nullptr;
@@ -4161,7 +4186,8 @@ CodeGenModule::GetAddrOfConstantCFString(const StringLiteral *Literal) {
 
     // Decay array -> ptr
     CFConstantStringClassRef =
-        llvm::ConstantExpr::getGetElementPtr(Ty, C, Zeros);
+        IsSwiftABI ? llvm::ConstantExpr::getPtrToInt(C, Ty)
+                   : llvm::ConstantExpr::getGetElementPtr(Ty, C, Zeros);
   }
 
   QualType CFTy = Context.getCFConstantStringType();
@@ -4175,7 +4201,12 @@ CodeGenModule::GetAddrOfConstantCFString(const StringLiteral *Literal) {
   Fields.add(cast<llvm::ConstantExpr>(CFConstantStringClassRef));
 
   // Flags.
-  Fields.addInt(IntTy, isUTF16 ? 0x07d0 : 0x07C8);
+  if (IsSwiftABI) {
+    Fields.addInt(IntPtrTy, IsSwift4_1 ? 0x05 : 0x01);
+    Fields.addInt(Int64Ty, isUTF16 ? 0x07d0 : 0x07c8);
+  } else {
+    Fields.addInt(IntTy, isUTF16 ? 0x07d0 : 0x07C8);
+  }
 
   // String pointer.
   llvm::Constant *C = nullptr;
@@ -4221,8 +4252,17 @@ CodeGenModule::GetAddrOfConstantCFString(const StringLiteral *Literal) {
   Fields.add(Str);
 
   // String length.
-  auto Ty = getTypes().ConvertType(Context.LongTy);
-  Fields.addInt(cast<llvm::IntegerType>(Ty), StringLength);
+  llvm::IntegerType *LengthTy =
+      llvm::IntegerType::get(getModule().getContext(),
+                             Context.getTargetInfo().getLongWidth());
+  if (IsSwiftABI) {
+    if (CFRuntime == LangOptions::CoreFoundationABI::Swift4_1 ||
+        CFRuntime == LangOptions::CoreFoundationABI::Swift4_2)
+      LengthTy = Int32Ty;
+    else
+      LengthTy = IntPtrTy;
+  }
+  Fields.addInt(LengthTy, StringLength);
 
   CharUnits Alignment = getPointerAlign();
 
-- 
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