[Demangler] Fix the name of float vector types in OldDemangler.

The OldDemangler was still spelling Builtin.Vec4xFPIEEE16 as
Builtin.Vec4xFloat16, which meant that feeding its output to the new
Remangler caused it to fail with "fatal error: unexpected builtin
vector type".

rdar://63485806

Author: al45tair

lib/Demangling/OldDemangler.cpp

@@ -1877,7 +1877,7 @@ class OldDemangler {
               return nullptr;
             return Factory.createNode(
                 Node::Kind::BuiltinTypeName,
-                (DemanglerPrinter() << "Builtin.Vec" << elts << "xFloat"
+                (DemanglerPrinter() << "Builtin.Vec" << elts << "xFPIEEE"
                                     << size).str());
           }
           if (Mangled.nextIf('p'))

lib/Demangling/OldRemangler.cpp

@@ -1178,7 +1178,7 @@ void Remangler::mangleBuiltinTypeName(Node *node) {
     auto element = text.substr(splitIdx).substr(1);
     if (element == "RawPointer") {
       Buffer << 'p';
-    } else if (stripPrefix(element, "Float")) {
+    } else if (stripPrefix(element, "FPIEEE")) {
       Buffer << 'f' << element << '_';
     } else if (stripPrefix(element, "Int")) {
       Buffer << 'i' << element << '_';

test/Demangle/Inputs/manglings.txt

@@ -12,8 +12,11 @@ _TtBo ---> Builtin.NativeObject
 _TtBp ---> Builtin.RawPointer
 _TtBt ---> Builtin.SILToken
 _TtBv4Bi8_ ---> Builtin.Vec4xInt8
-_TtBv4Bf16_ ---> Builtin.Vec4xFloat16
+_TtBv4Bf16_ ---> Builtin.Vec4xFPIEEE16
 _TtBv4Bp ---> Builtin.Vec4xRawPointer
+$sBi8_Bv4_ ---> Builtin.Vec4xInt8
+$sBf16_Bv4_ ---> Builtin.Vec4xFPIEEE16
+$sBpBv4_ ---> Builtin.Vec4xRawPointer
 _TtSa ---> Swift.Array
 _TtSb ---> Swift.Bool
 _TtSc ---> Swift.UnicodeScalar

test/Demangle/Inputs/simplified-manglings.txt

@@ -5,7 +5,7 @@ _TtBO ---> Builtin.UnknownObject
 _TtBo ---> Builtin.NativeObject
 _TtBp ---> Builtin.RawPointer
 _TtBv4Bi8_ ---> Builtin.Vec4xInt8
-_TtBv4Bf16_ ---> Builtin.Vec4xFloat16
+_TtBv4Bf16_ ---> Builtin.Vec4xFPIEEE16
 _TtBv4Bp ---> Builtin.Vec4xRawPointer
 _TtSa ---> Array
 _TtSb ---> Bool