Introduce _va_list_kind conditional. Use it for VarArgs implementation.

In order to simplify the logic for CVaListPtr and __VaListBuilder,
introduce a new kind of conditional _va_list_kind which will be
populated from the equivalent enumeration in
clang::TargetInfo::BuiltinVaListKind.

Author: drodriguez

include/swift/Basic/LangOptions.h

@@ -50,6 +50,8 @@ namespace swift {
     CanImport,
     /// Target Environment (currently just 'simulator' or absent)
     TargetEnvironment,
+    /// Variable argument list standard
+    VariableArgumentList,
   };
 
   /// Describes which Swift 3 Objective-C inference warnings should be
@@ -388,7 +390,7 @@ namespace swift {
     }
 
   private:
-    llvm::SmallVector<std::pair<PlatformConditionKind, std::string>, 5>
+    llvm::SmallVector<std::pair<PlatformConditionKind, std::string>, 6>
         PlatformConditionValues;
     llvm::SmallVector<std::string, 2> CustomConditionalCompilationFlags;
   };

lib/Basic/LangOptions.cpp

@@ -19,6 +19,7 @@
 #include "swift/Basic/Platform.h"
 #include "swift/Basic/Range.h"
 #include "swift/Config.h"
+#include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/raw_ostream.h"
@@ -65,6 +66,17 @@ static const StringRef SupportedConditionalCompilationTargetEnvironments[] = {
   "simulator",
 };
 
+static const StringRef SupportedConditionalCompilationVariableArgumentLists[] = {
+  "_charPtr",
+  "_voidPtr",
+  "_aarch64",
+  "_pnacl",
+  "_power",
+  "_x86_64",
+  "_aapcs",
+  "_systemZ",
+};
+
 template <size_t N>
 bool contains(const StringRef (&Array)[N], const StringRef &V,
               std::vector<StringRef> &suggestions) {
@@ -107,6 +119,9 @@ checkPlatformConditionSupported(PlatformConditionKind Kind, StringRef Value,
   case PlatformConditionKind::TargetEnvironment:
     return contains(SupportedConditionalCompilationTargetEnvironments, Value,
                     suggestions);
+  case PlatformConditionKind::VariableArgumentList:
+    return contains(SupportedConditionalCompilationVariableArgumentLists, Value,
+                    suggestions);
   case PlatformConditionKind::CanImport:
     // All importable names are valid.
     // FIXME: Perform some kind of validation of the string?
@@ -269,6 +284,35 @@ std::pair<bool, bool> LangOptions::setTarget(llvm::Triple triple) {
     addPlatformConditionValue(PlatformConditionKind::TargetEnvironment,
                               "simulator");
 
+  // Set the "_va_list_kind" platform condition.
+  clang::TargetInfo *TargetInfo = NULL; // TODO: how?
+  switch (TargetInfo->getBuiltinVaListKind()) {
+    case clang::TargetInfo::CharPtrBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_charPtr");
+      break;
+    case clang::TargetInfo::VoidPtrBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_voidPtr");
+      break;
+    case clang::TargetInfo::AArch64ABIBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_aarch64");
+      break;
+    case clang::TargetInfo::PNaClABIBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_pnacl");
+      break;
+    case clang::TargetInfo::PowerABIBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_power");
+      break;
+    case clang::TargetInfo::X86_64ABIBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_x86_64");
+      break;
+    case clang::TargetInfo::AAPCSABIBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_aapcs");
+      break;
+    case clang::TargetInfo::SystemZBuiltinVaList:
+      addPlatformConditionValue(PlatformConditionKind::VariableArgumentList, "_systemZ");
+      break;
+  }
+
   // If you add anything to this list, change the default size of
   // PlatformConditionValues to not require an extra allocation
   // in the common case.

lib/Parse/ParseIfConfig.cpp

@@ -43,6 +43,7 @@ Optional<PlatformConditionKind> getPlatformConditionKind(StringRef Name) {
     .Case("_runtime", PlatformConditionKind::Runtime)
     .Case("canImport", PlatformConditionKind::CanImport)
     .Case("targetEnvironment", PlatformConditionKind::TargetEnvironment)
+    .Case("_va_list_kind", PlatformConditionKind::VariableArgumentList)
     .Default(None);
 }
 
@@ -287,6 +288,8 @@ class ValidateIfConfigCondition :
         DiagName = "import conditional"; break;
       case PlatformConditionKind::TargetEnvironment:
         DiagName = "target environment"; break;
+      case PlatformConditionKind::VariableArgumentList:
+        DiagName = "variable argument list kind"; break;
       case PlatformConditionKind::Runtime:
         llvm_unreachable("handled above");
       }

stdlib/public/core/CTypes.swift

@@ -219,7 +219,7 @@ extension UInt {
 }
 
 /// A wrapper around a C `va_list` pointer.
-#if arch(arm64) && os(Linux)
+#if _va_list_kind(_aarch64)
 @_fixed_layout
 public struct CVaListPointer {
   @usableFromInline // unsafe-performance

stdlib/public/core/VarArgs.swift

@@ -63,7 +63,7 @@ protocol _CVarArgAligned : CVarArg {
   var _cVarArgAlignment: Int { get }
 }
 
-#if arch(x86_64)
+#if _va_list_kind(_x86_64)
 @usableFromInline
 internal let _countGPRegisters = 6
 // Note to future visitors concerning the following SSE register count.
@@ -91,7 +91,7 @@ internal let _countGPRegisters = 16
 @usableFromInline
 internal let _registerSaveWords = _countGPRegisters
 
-#elseif arch(arm64) && os(Linux)
+#elseif _va_list_kind(_aarch64)
 // ARM Procedure Call Standard for aarch64. (IHI0055B)
 // The va_list type may refer to any parameter in a parameter list may be in one
 // of three memory locations depending on its type and position in the argument
@@ -109,7 +109,7 @@ internal let _fpRegisterWords = 16 /  MemoryLayout<Int>.size
 internal let _registerSaveWords = _countGPRegisters + (_countFPRegisters * _fpRegisterWords)
 #endif
 
-#if arch(s390x)
+#if _va_list_kind(_systemZ)
 @usableFromInline
 internal typealias _VAUInt = CUnsignedLongLong
 @usableFromInline
@@ -419,7 +419,7 @@ extension Float80 : CVarArg, _CVarArgAligned {
 }
 #endif
 
-#if arch(x86_64) || arch(s390x)
+#if _va_list_kind(_x86_64) || _va_list_kind(_systemZ)
 
 /// An object that can manage the lifetime of storage backing a
 /// `CVaListPointer`.
@@ -470,7 +470,7 @@ final internal class __VaListBuilder {
   internal func append(_ arg: CVarArg) {
     var encoded = arg._cVarArgEncoding
 
-#if arch(x86_64)
+#if _va_list_kind(_x86_64)
     let isDouble = arg is _CVarArgPassedAsDouble
 
     if isDouble && fpRegistersUsed < _countFPRegisters {
@@ -493,7 +493,7 @@ final internal class __VaListBuilder {
         storage.append(w)
       }
     }
-#elseif arch(s390x)
+#elseif _va_list_kind(_systemZ)
     if gpRegistersUsed < _countGPRegisters {
       for w in encoded {
         storage[gpRegistersUsed] = w
@@ -518,7 +518,7 @@ final internal class __VaListBuilder {
                Builtin.addressof(&self.header)))
   }
 }
-#elseif arch(arm64) && os(Linux)
+#elseif _va_list_kind(_aarch64)
 
 // NOTE: older runtimes called this _VaListBuilder. The two must
 // coexist, so it was renamed. The old name must not be used in the new