Merge pull request #66050 from al45tair/eng/PR-109649226-5.9

[Tools] Fix macro demangling.

Author: al45tair

tools/swift-demangle/swift-demangle.cpp

@@ -271,7 +271,7 @@ static bool findMaybeMangled(llvm::StringRef input, llvm::StringRef &match) {
   } state = Start;
   const char *matchStart = nullptr;
 
-  // Find _T, $S, $s, _$S, _$s, @__swift_ followed by a valid mangled string
+  // Find _T, $S, $s, _$S, _$s, @__swiftmacro_ followed by a valid mangled string
   while (ptr < end) {
     switch (state) {
     case Start:
@@ -289,7 +289,7 @@ static bool findMaybeMangled(llvm::StringRef input, llvm::StringRef &match) {
         } else if (ch == '@' &&
                    llvm::StringRef(ptr, end - ptr).startswith("__swiftmacro_")){
           matchStart = ptr - 1;
-          ptr = ptr + strlen("__swift_");
+          ptr = ptr + strlen("__swiftmacro_");
           state = FoundPrefix;
           break;
         }