[Verifier] Extend address taken check for unknown intrinsics

[nikic]

Summary

Intrinsics can only be called directly, taking their address is not legal. This is currently only enforced for intrinsics that have an ID, rather than all intrinsics. Adjust the check to cover all intrinsics.

This came up in D106013.

llvm/lib/IR/Verifier.cpp

for (const auto &I : MDs) {
       visitMDNode(*I.second, AllowLocs);
     }
   }
 
   // If this function is actually an intrinsic, verify that it is only used in
   // direct call/invokes, never having its "address taken".
   // Only do this if the module is materialized, otherwise we don't have all the
   // uses.
-  if (F.getIntrinsicID() && F.getParent()->isMaterialized()) {
+  if (F.isIntrinsic() && F.getParent()->isMaterialized()) {
     const User *U;
     if (F.hasAddressTaken(&U))
       Assert(false, "Invalid user of intrinsic instruction!", U);
   }
 
   // Check intrinsics' signatures.
   switch (F.getIntrinsicID()) {
   case Intrinsic::experimental_gc_get_pointer_base: {

llvm/test/Verifier/intrinsic-addr-taken.ll

+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+declare i32 @llvm.umax.i32(i32, i32)
+declare i32 @llvm.my.custom.intrinsic()
+
+; CHECK: Invalid user of intrinsic instruction!
+@g1 = global i32(i32, i32)* @llvm.umax.i32
+; CHECK: Invalid user of intrinsic instruction!
+@g2 = global i32()* @llvm.my.custom.intrinsic