Handle Is and IsNot in irgen

ie instead of generating the call to compare(AST_TYPE::Is), just
directly do the pointer comparison in LLVM IR.

src/codegen/baseline_jit.cpp

@@ -176,6 +176,8 @@ RewriterVar* JitFragmentWriter::emitCallattr(RewriterVar* obj, BoxedString* attr
 }
 
 RewriterVar* JitFragmentWriter::emitCompare(RewriterVar* lhs, RewriterVar* rhs, int op_type) {
+// TODO: can directly emit the assembly for Is/IsNot
+
 #if ENABLE_BASELINEJIT_ICS
     return call(false, (void*)compareICHelper, imm(new CompareIC), lhs, rhs, imm(op_type));
 #else

src/codegen/irgen/irgenerator.cpp

@@ -811,6 +811,20 @@ private:
         assert(left);
         assert(right);
 
+        if (node->ops[0] == AST_TYPE::Is || node->ops[0] == AST_TYPE::IsNot) {
+            // TODO: I think we can do better here and not force the types to box themselves
+
+            ConcreteCompilerVariable* converted_left = left->makeConverted(emitter, UNKNOWN);
+            ConcreteCompilerVariable* converted_right = right->makeConverted(emitter, UNKNOWN);
+            llvm::Value* cmp;
+            if (node->ops[0] == AST_TYPE::Is)
+                cmp = emitter.getBuilder()->CreateICmpEQ(converted_left->getValue(), converted_right->getValue());
+            else
+                cmp = emitter.getBuilder()->CreateICmpNE(converted_left->getValue(), converted_right->getValue());
+
+            return boolFromI1(emitter, cmp);
+        }
+
         CompilerVariable* rtn = _evalBinExp(node, left, right, node->ops[0], Compare, unw_info);
         left->decvref(emitter);
         right->decvref(emitter);