[SVE] Fix unsigned is always >= 0

[sdesmalen]

LGTM, thanks for fixing @ctetreau!

clang/utils/TableGen/SveEmitter.cpp

void SVEEmitter::createIntrinsic(
   TypeSpecs.erase(std::unique(TypeSpecs.begin(), TypeSpecs.end()),
                   TypeSpecs.end());
 
   // Create an Intrinsic for each type spec.
   for (auto TS : TypeSpecs) {
     // Collate a list of range/option checks for the immediates.
     SmallVector<ImmCheck, 2> ImmChecks;
     for (auto *R : ImmCheckList) {
-      unsigned Arg = R->getValueAsInt("Arg");
-      unsigned EltSizeArg = R->getValueAsInt("EltSizeArg");
-      unsigned Kind = R->getValueAsDef("Kind")->getValueAsInt("Value");
+      int64_t Arg = R->getValueAsInt("Arg");
+      int64_t EltSizeArg = R->getValueAsInt("EltSizeArg");
+      int64_t Kind = R->getValueAsDef("Kind")->getValueAsInt("Value");
+      assert(Arg >= 0 && Kind >= 0 && "Arg and Kind must be nonnegative");
 
       unsigned ElementSizeInBits = 0;
       if (EltSizeArg >= 0)
         ElementSizeInBits =
             SVEType(TS, Proto[EltSizeArg + /* offset by return arg */ 1])
                 .getElementSizeInBits();
       ImmChecks.push_back(ImmCheck(Arg, Kind, ElementSizeInBits));
     }