diff --git a/src/detail/x86_64_unix.rs b/src/detail/x86_64_unix.rs
index 9182e2f..47b5060 100644
--- a/src/detail/x86_64_unix.rs
+++ b/src/detail/x86_64_unix.rs
@@ -16,7 +16,7 @@ mod asm_impl {
     /// prefetch data
     #[inline]
     pub unsafe extern "C" fn prefetch(data: *const usize) {
-        asm!(
+        llvm_asm!(
             "prefetcht1 $0"
             : // no output
             : "m"(*data)
@@ -28,7 +28,7 @@ mod asm_impl {
     #[naked]
     #[inline(never)]
     pub unsafe extern "C" fn bootstrap_green_task() {
-        asm!(
+        llvm_asm!(
             "
                 mov %r12, %rdi     // setup the function arg
                 mov %r13, %rsi     // setup the function arg
@@ -46,7 +46,7 @@ mod asm_impl {
     #[inline(never)]
     pub unsafe extern "C" fn swap_registers(out_regs: *mut Registers, in_regs: *const Registers) {
         // The first argument is in %rdi, and the second one is in %rsi
-        asm!(
+        llvm_asm!(
             ""
             :
             : "{rdi}"(out_regs), "{rsi}"(in_regs)
@@ -58,7 +58,7 @@ mod asm_impl {
         #[naked]
         unsafe extern "C" fn _swap_reg() {
             // Save registers
-            asm!(
+            llvm_asm!(
                 "
                     mov %rbx, (0*8)(%rdi)
                     mov %rsp, (1*8)(%rdi)
diff --git a/src/detail/x86_64_windows.rs b/src/detail/x86_64_windows.rs
index 96d49fe..1a27855 100644
--- a/src/detail/x86_64_windows.rs
+++ b/src/detail/x86_64_windows.rs
@@ -22,7 +22,7 @@ mod asm_impl {
     /// prefetch data
     #[inline]
     pub unsafe extern "C" fn prefetch_asm(data: *const usize) {
-        asm!(
+        llvm_asm!(
             "prefetcht1 $0"
             : // no output
             : "m"(*data)
@@ -34,7 +34,7 @@ mod asm_impl {
     #[naked]
     #[inline(never)]
     pub unsafe extern "C" fn bootstrap_green_task() {
-        asm!(
+        llvm_asm!(
             "
                 mov %r12, %rcx     // setup the function arg
                 mov %r13, %rdx     // setup the function arg
@@ -52,7 +52,7 @@ mod asm_impl {
     #[inline(never)]
     pub unsafe extern "C" fn swap_registers(out_regs: *mut Registers, in_regs: *const Registers) {
         // The first argument is in %rcx, and the second one is in %rdx
-        asm!(
+        llvm_asm!(
             ""
             :
             : "{rcx}"(out_regs), "{rdx}"(in_regs)
@@ -64,7 +64,7 @@ mod asm_impl {
         #[naked]
         unsafe extern "C" fn _swap_reg() {
             // Save registers
-            asm!(
+            llvm_asm!(
                 "
                     mov %rbx, (0*8)(%rcx)
                     mov %rsp, (1*8)(%rcx)
diff --git a/src/gen_impl.rs b/src/gen_impl.rs
index 952a440..332f584 100644
--- a/src/gen_impl.rs
+++ b/src/gen_impl.rs
@@ -115,8 +115,11 @@ impl<'a, A, T> Generator<'a, A, T> {
         self.gen.send(para)
     }
 
-    /// cancel the generator
-    /// this will trigger a Cancel panic, it's unsafe in that you must care about the resource
+    /// cancel the generator [TODO: change to safe?]
+    /// this will trigger a Cancel panic
+    /// # Safety
+    /// it's unsafe that cancel may have side effect when unwind stack
+    /// all the resources would be dropped before the normal completion
     pub unsafe fn cancel(&mut self) {
         self.gen.cancel()
     }
diff --git a/src/lib.rs b/src/lib.rs
index 6d3afde..475f835 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@
 //! Rust generator library
 //!
 
-#![cfg_attr(nightly, feature(asm))]
+#![cfg_attr(nightly, feature(llvm_asm))]
 #![cfg_attr(nightly, feature(repr_simd))]
 #![cfg_attr(nightly, feature(core_intrinsics))]
 #![cfg_attr(nightly, feature(naked_functions))]
diff --git a/src/rt.rs b/src/rt.rs
index 4132ffd..887d228 100644
--- a/src/rt.rs
+++ b/src/rt.rs
@@ -24,6 +24,7 @@ thread_local!(
 // to a different place, be careful about that.
 #[cfg(nightly)]
 #[thread_local]
+#[no_mangle]
 static mut ROOT_CONTEXT_P: *mut Context = ptr::null_mut();
 
 /// yield panic error types
diff --git a/tests/lib.rs b/tests/lib.rs
index bd0bff8..38a5f58 100644
--- a/tests/lib.rs
+++ b/tests/lib.rs
@@ -1,4 +1,5 @@
 #![allow(deprecated)]
+#![allow(unused_assignments)]
 
 extern crate generator;