Fix assertion failure in LLParser::ConvertValIDToValue

[kschimpf]

Summary

Fixes bug 24645. Problem appears to be that the type may be undefined
when ConvertValIDToValue is called.

[kcc]

Fix is ok, but please add a test.

I've never seen this code before today, but the fix is obvious so I hope my LGTM should be enough.

[kschimpf]

Add test case.

[kschimpf]

Added test case to demonstrate bug https://llvm.org/bugs/show_bug.cgi?id=24645 is fixed.

Since kcc and myself are not familiar with the code, does anyone have any objections to this fix?

[kcc]

LGTM

[kschimpf]

Committed. See http://reviews.llvm.org/rL246779

lib/AsmParser/LLParser.h

enum {
       t_Constant,                 // Value in ConstantVal.
       t_InlineAsm,                // Value in FTy/StrVal/StrVal2/UIntVal.
       t_ConstantStruct,           // Value in ConstantStructElts.
       t_PackedConstantStruct      // Value in ConstantStructElts.
     } Kind = t_LocalID;
 
     LLLexer::LocTy Loc;
     unsigned UIntVal;
-    FunctionType *FTy;
+    FunctionType *FTy = nullptr;
     std::string StrVal, StrVal2;
     APSInt APSIntVal;
     APFloat APFloatVal{0.0};
     Constant *ConstantVal;
     std::unique_ptr<Constant *[]> ConstantStructElts;
 
     ValID() = default;
     ValID(const ValID &RHS)

lib/AsmParser/LLParser.cpp

case ValID::t_LocalID:
     if (!PFS) return Error(ID.Loc, "invalid use of function-local name");
     V = PFS->GetVal(ID.UIntVal, Ty, ID.Loc, OC);
     return V == nullptr;
   case ValID::t_LocalName:
     if (!PFS) return Error(ID.Loc, "invalid use of function-local name");
     V = PFS->GetVal(ID.StrVal, Ty, ID.Loc, OC);
     return V == nullptr;
   case ValID::t_InlineAsm: {
-    assert(ID.FTy);
-    if (!InlineAsm::Verify(ID.FTy, ID.StrVal2))
+    if (!ID.FTy || !InlineAsm::Verify(ID.FTy, ID.StrVal2))
       return Error(ID.Loc, "invalid type for inline asm constraint string");
     V = InlineAsm::get(ID.FTy, ID.StrVal, ID.StrVal2, ID.UIntVal & 1,
                        (ID.UIntVal >> 1) & 1,
                        (InlineAsm::AsmDialect(ID.UIntVal >> 2)));
     return false;
   }
   case ValID::t_GlobalName:
     V = GetGlobalVal(ID.StrVal, Ty, ID.Loc);

test/Assembler/invalid-untyped-metadata.ll

+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+; Tests bug: https://llvm.org/bugs/show_bug.cgi?id=24645
+; CHECK: error: invalid type for inline asm constraint string
+
+     !3=!    {%..d04 *asm" !6!={!H)4" ,""