diff --git a/clang/include/clang/Basic/SourceLocation.h b/clang/include/clang/Basic/SourceLocation.h
--- a/clang/include/clang/Basic/SourceLocation.h
+++ b/clang/include/clang/Basic/SourceLocation.h
@@ -132,9 +132,18 @@
   }
 
 public:
-  /// Return a source location with the specified offset from this
+  /// Return a source location with a specified offset from this
   /// SourceLocation.
-  SourceLocation getLocWithOffset(IntType Offset) const {
+  ///
+  /// If the second parameter NegOffset is provided, then the combined offset
+  /// is computed as Offset - NegOffset. This is convenient if the desired
+  /// offset is held in a 32-bit integer type such as `unsigned`, but
+  /// SourceLocations are 64 bits: if you compute a negative offset in an
+  /// unsigned without widening it first, it becomes positive again. Allowing
+  /// the subtraction to be done inside this function avoids a cumbersome cast
+  /// at every call site.
+  SourceLocation getLocWithOffset(IntType Offset, IntType NegOffset = 0) const {
+    Offset -= NegOffset;
     assert(((getOffset()+Offset) & MacroIDBit) == 0 && "offset overflow");
     SourceLocation L;
     L.ID = ID+Offset;
diff --git a/clang/lib/AST/SelectorLocationsKind.cpp b/clang/lib/AST/SelectorLocationsKind.cpp
--- a/clang/lib/AST/SelectorLocationsKind.cpp
+++ b/clang/lib/AST/SelectorLocationsKind.cpp
@@ -28,7 +28,7 @@
       return SourceLocation();
     IdentifierInfo *II = Sel.getIdentifierInfoForSlot(0);
     unsigned Len = II ? II->getLength() : 0;
-    return EndLoc.getLocWithOffset(-Len);
+    return EndLoc.getLocWithOffset(0, Len);
   }
 
   assert(Index < NumSelArgs);
@@ -38,7 +38,7 @@
   unsigned Len = /* selector id */ (II ? II->getLength() : 0) + /* ':' */ 1;
   if (WithArgSpace)
     ++Len;
-  return ArgLoc.getLocWithOffset(-Len);
+  return ArgLoc.getLocWithOffset(0, Len);
 }
 
 namespace {
diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -233,7 +233,7 @@
   /// Return the start location of an included file or expanded macro.
   SourceLocation getStartOfFileOrMacro(SourceLocation Loc) {
     if (Loc.isMacroID())
-      return Loc.getLocWithOffset(-SM.getFileOffset(Loc));
+      return Loc.getLocWithOffset(0, SM.getFileOffset(Loc));
     return SM.getLocForStartOfFile(SM.getFileID(Loc));
   }
 
diff --git a/clang/lib/Format/FormatTokenLexer.cpp b/clang/lib/Format/FormatTokenLexer.cpp
--- a/clang/lib/Format/FormatTokenLexer.cpp
+++ b/clang/lib/Format/FormatTokenLexer.cpp
@@ -832,7 +832,7 @@
   FormatTok = new (Allocator.Allocate()) FormatToken;
   readRawToken(*FormatTok);
   SourceLocation WhitespaceStart =
-      FormatTok->Tok.getLocation().getLocWithOffset(-TrailingWhitespace);
+      FormatTok->Tok.getLocation().getLocWithOffset(0, TrailingWhitespace);
   FormatTok->IsFirst = IsFirstToken;
   IsFirstToken = false;
 
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -527,7 +527,7 @@
     return Loc;
 
   // Create a lexer starting at the beginning of this token.
-  SourceLocation LexerStartLoc = Loc.getLocWithOffset(-LocInfo.second);
+  SourceLocation LexerStartLoc = Loc.getLocWithOffset(0, LocInfo.second);
   Lexer TheLexer(LexerStartLoc, LangOpts, Buffer.data(), LexStart,
                  Buffer.end());
   TheLexer.SetCommentRetentionState(true);
@@ -570,7 +570,7 @@
       SM.getDecomposedLoc(BeginFileLoc);
   assert(FileLocInfo.first == BeginFileLocInfo.first &&
          FileLocInfo.second >= BeginFileLocInfo.second);
-  return Loc.getLocWithOffset(BeginFileLocInfo.second - FileLocInfo.second);
+  return Loc.getLocWithOffset(BeginFileLocInfo.second, FileLocInfo.second);
 }
 
 namespace {
diff --git a/clang/lib/Parse/ParseStmtAsm.cpp b/clang/lib/Parse/ParseStmtAsm.cpp
--- a/clang/lib/Parse/ParseStmtAsm.cpp
+++ b/clang/lib/Parse/ParseStmtAsm.cpp
@@ -185,7 +185,7 @@
   if (TokIndex < AsmToks.size()) {
     const Token &Tok = AsmToks[TokIndex];
     Loc = Tok.getLocation();
-    Loc = Loc.getLocWithOffset(Offset - TokOffset);
+    Loc = Loc.getLocWithOffset(Offset, TokOffset);
   }
   return Loc;
 }
diff --git a/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp b/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
--- a/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
+++ b/clang/lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp
@@ -1081,8 +1081,7 @@
   // Highlight the range.  Make the span tag the outermost tag for the
   // selected range.
 
-  SourceLocation E =
-    InstantiationEnd.getLocWithOffset(EndColNo - OldEndColNo);
+  SourceLocation E = InstantiationEnd.getLocWithOffset(EndColNo, OldEndColNo);
 
   html::HighlightRange(R, InstantiationStart, E, HighlightStart, HighlightEnd);
 }