[Local] Remove handling for lifetime intrinsic on non-alloca (NFC)

After llvm#149310 this is guaranteed to be an alloca.

Author: nikic

llvm/lib/Transforms/Utils/Local.cpp

@@ -482,16 +482,11 @@ bool llvm::wouldInstructionBeTriviallyDead(const Instruction *I,
 
     if (II->isLifetimeStartOrEnd()) {
       auto *Arg = II->getArgOperand(1);
-      // Lifetime intrinsics are dead when their right-hand is undef.
-      if (isa<UndefValue>(Arg))
-        return true;
-      // If the right-hand is an alloc, global, or argument and the only uses
-      // are lifetime intrinsics then the intrinsics are dead.
-      if (isa<AllocaInst>(Arg) || isa<GlobalValue>(Arg) || isa<Argument>(Arg))
-        return llvm::all_of(Arg->uses(), [](Use &Use) {
-          return isa<LifetimeIntrinsic>(Use.getUser());
-        });
-      return false;
+      // If the only uses of the alloca are lifetime intrinsics, then the
+      // intrinsics are dead.
+      return llvm::all_of(Arg->uses(), [](Use &Use) {
+        return isa<LifetimeIntrinsic>(Use.getUser());
+      });
     }
 
     // Assumptions are dead if their condition is trivially true.