[clang] Add getSignedSizeType method

C11 standard refers to the signed counterpart of the type size_t in
the paragraph 7.21.6.1 where it defines d, i, o, u, x, or x conversion specifiers
(in printf format string).
In Clang there is a FIXME (in lib/Analysis/PrintfFormatString.cpp) for this case
(which is not handled correctly at the moment).
This diff adds getSignedSizeType method to TargetInfo and exposes it 
in ASTContext similarly to how it is done for getSizeType.
lib/Analysis/PrintfFormatString.cpp will be changed in a separate commit.

Differential revision: https://reviews.llvm.org/D35378

Test plan: make check-all

llvm-svn: 308037

clang/include/clang/AST/ASTContext.h

@@ -1441,6 +1441,10 @@ class ASTContext : public RefCountedBase<ASTContext> {
   /// The sizeof operator requires this (C99 6.5.3.4p4).
   CanQualType getSizeType() const;
 
+  /// \brief Return the unique signed counterpart of 
+  /// the integer type corresponding to size_t.
+  CanQualType getSignedSizeType() const;
+
   /// \brief Return the unique type for "intmax_t" (C99 7.18.1.5), defined in
   /// <stdint.h>.
   CanQualType getIntMaxType() const;

clang/include/clang/Basic/TargetInfo.h

@@ -226,6 +226,20 @@ class TargetInfo : public RefCountedBase<TargetInfo> {
 
 public:
   IntType getSizeType() const { return SizeType; }
+  IntType getSignedSizeType() const {
+    switch (SizeType) {
+    case UnsignedShort:
+      return SignedShort;
+    case UnsignedInt:
+      return SignedInt;
+    case UnsignedLong:
+      return SignedLong;
+    case UnsignedLongLong:
+      return SignedLongLong;
+    default:
+      llvm_unreachable("Invalid SizeType");
+    }
+  }
   IntType getIntMaxType() const { return IntMaxType; }
   IntType getUIntMaxType() const {
     return getCorrespondingUnsignedType(IntMaxType);

clang/lib/AST/ASTContext.cpp

@@ -4525,6 +4525,12 @@ CanQualType ASTContext::getSizeType() const {
   return getFromTargetType(Target->getSizeType());
 }
 
+/// Return the unique signed counterpart of the integer type 
+/// corresponding to size_t.
+CanQualType ASTContext::getSignedSizeType() const {
+  return getFromTargetType(Target->getSignedSizeType());
+}
+
 /// getIntMaxType - Return the unique type for "intmax_t" (C99 7.18.1.5).
 CanQualType ASTContext::getIntMaxType() const {
   return getFromTargetType(Target->getIntMaxType());