[clang] Add getSignedSizeType method

[alexander-shaposhnikov]

Summary

This is a follow-up for the discussion on cfe-dev.
C11 standard refers to the signed counterpart of the size_t type 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 is supposed to be changed in a separate commit.

[alexander-shaposhnikov]

make comments consistent

[rnk]

lgtm

include/clang/AST/ASTContext.h

public:
   QualType getTagDeclType(const TagDecl *Decl) const;
 
   /// \brief Return the unique type for "size_t" (C99 7.17), defined in
   /// <stddef.h>.
   ///
   /// 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;
 
   /// \brief Return the unique type for "uintmax_t" (C99 7.18.1.5), defined in
   /// <stdint.h>.
   CanQualType getUIntMaxType() const;
 

include/clang/Basic/TargetInfo.h

protected:
   unsigned ZeroLengthBitfieldBoundary;
 
   /// \brief Specify if mangling based on address space map should be used or
   /// not for language specific address spaces
   bool UseAddrSpaceMapMangling;
 
 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);
   }
   IntType getPtrDiffType(unsigned AddrSpace) const {
     return AddrSpace == 0 ? PtrDiffType : getPtrDiffTypeV(AddrSpace);
   }
   IntType getIntPtrType() const { return IntPtrType; }

lib/AST/ASTContext.cpp

 
 /// getSizeType - Return the unique type for "size_t" (C99 7.17), the result
 /// of the sizeof operator (C99 6.5.3.4p4). The value is target dependent and
 /// needs to agree with the definition in <stddef.h>.
 CanQualType ASTContext::getSizeType() const {
   return getFromTargetType(Target->getSizeType());
 }
 
+/// Return the unique signed 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());
 }
 
 /// getUIntMaxType - Return the unique type for "uintmax_t" (C99 7.18.1.5).
 CanQualType ASTContext::getUIntMaxType() const {
   return getFromTargetType(Target->getUIntMaxType());