diff --git a/py/nlr.c b/py/nlr.c
new file mode 100644
index 0000000000..e4d6d10c0b
--- /dev/null
+++ b/py/nlr.c
@@ -0,0 +1,74 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2017 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/mpstate.h"
+
+// Helper macros to save/restore the pystack state
+#if MICROPY_ENABLE_PYSTACK
+#define MP_NLR_SAVE_PYSTACK(nlr_buf) (nlr_buf)->pystack = MP_STATE_THREAD(pystack_cur)
+#define MP_NLR_RESTORE_PYSTACK(nlr_buf) MP_STATE_THREAD(pystack_cur) = (nlr_buf)->pystack
+#else
+#define MP_NLR_SAVE_PYSTACK(nlr_buf) (void)nlr_buf
+#define MP_NLR_RESTORE_PYSTACK(nlr_buf) (void)nlr_buf
+#endif
+
+#if !MICROPY_NLR_SETJMP
+// When not using setjmp, nlr_push_tail is called from inline asm so needs special care
+#if MICROPY_NLR_X86 && (defined(_WIN32) || defined(__CYGWIN__))
+// On these 32-bit platforms make sure nlr_push_tail doesn't have a leading underscore
+unsigned int nlr_push_tail(nlr_buf_t *nlr) asm("nlr_push_tail");
+#else
+// LTO can't see inside inline asm functions so explicitly mark nlr_push_tail as used
+__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr);
+#endif
+#endif
+
+unsigned int nlr_push_tail(nlr_buf_t *nlr) {
+    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
+    nlr->prev = *top;
+    MP_NLR_SAVE_PYSTACK(nlr);
+    *top = nlr;
+    return 0; // normal return
+}
+
+void nlr_pop(void) {
+    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
+    *top = (*top)->prev;
+}
+
+NORETURN void nlr_jump(void *val) {
+    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
+    nlr_buf_t *top = *top_ptr;
+    if (top == NULL) {
+        nlr_jump_fail(val);
+    }
+
+    top->ret_val = val;
+    MP_NLR_RESTORE_PYSTACK(top);
+    *top_ptr = top->prev;
+
+    nlr_jump_tail(top);
+}
diff --git a/py/nlr.h b/py/nlr.h
index 1235f14609..012a73c311 100644
--- a/py/nlr.h
+++ b/py/nlr.h
@@ -30,29 +30,29 @@
 // exception handling, basically a stack of setjmp/longjmp buffers
 
 #include <limits.h>
-#include <setjmp.h>
 #include <assert.h>
 
 #include "py/mpconfig.h"
 
-typedef struct _nlr_buf_t nlr_buf_t;
-struct _nlr_buf_t {
-    // the entries here must all be machine word size
-    nlr_buf_t *prev;
-    void *ret_val; // always a concrete object (an exception instance)
-#if !defined(MICROPY_NLR_SETJMP) || !MICROPY_NLR_SETJMP
+// If MICROPY_NLR_SETJMP is not enabled then auto-detect the machine arch
+// Allow a port to set MICROPY_NLR_NUM_REGS to define their own implementation
+#if !MICROPY_NLR_SETJMP && !defined(MICROPY_NLR_NUM_REGS)
 #if defined(__i386__)
-    void *regs[6];
+    #define MICROPY_NLR_X86 (1)
+    #define MICROPY_NLR_NUM_REGS (6)
 #elif defined(__x86_64__)
-  #if defined(__CYGWIN__)
-    void *regs[12];
-  #else
-    void *regs[8];
-  #endif
+    #define MICROPY_NLR_X64 (1)
+    #if defined(__CYGWIN__)
+        #define MICROPY_NLR_NUM_REGS (12)
+    #else
+        #define MICROPY_NLR_NUM_REGS (8)
+    #endif
 #elif defined(__thumb2__) || defined(__thumb__) || defined(__arm__)
-    void *regs[10];
+    #define MICROPY_NLR_THUMB (1)
+    #define MICROPY_NLR_NUM_REGS (10)
 #elif defined(__xtensa__)
-    void *regs[10];
+    #define MICROPY_NLR_XTENSA (1)
+    #define MICROPY_NLR_NUM_REGS (10)
 #else
     #define MICROPY_NLR_SETJMP (1)
     //#warning "No native NLR support for this arch, using setjmp implementation"
@@ -60,41 +60,39 @@ struct _nlr_buf_t {
 #endif
 
 #if MICROPY_NLR_SETJMP
-    jmp_buf jmpbuf;
+#include <setjmp.h>
 #endif
 
+typedef struct _nlr_buf_t nlr_buf_t;
+struct _nlr_buf_t {
+    // the entries here must all be machine word size
+    nlr_buf_t *prev;
+    void *ret_val; // always a concrete object (an exception instance)
+
+    #if MICROPY_NLR_SETJMP
+    jmp_buf jmpbuf;
+    #else
+    void *regs[MICROPY_NLR_NUM_REGS];
+    #endif
+
     #if MICROPY_ENABLE_PYSTACK
     void *pystack;
     #endif
 };
 
-// Helper macros to save/restore the pystack state
-#if MICROPY_ENABLE_PYSTACK
-#define MP_NLR_SAVE_PYSTACK(nlr_buf) (nlr_buf)->pystack = MP_STATE_THREAD(pystack_cur)
-#define MP_NLR_RESTORE_PYSTACK(nlr_buf) MP_STATE_THREAD(pystack_cur) = (nlr_buf)->pystack
-#else
-#define MP_NLR_SAVE_PYSTACK(nlr_buf) (void)nlr_buf
-#define MP_NLR_RESTORE_PYSTACK(nlr_buf) (void)nlr_buf
-#endif
-
 #if MICROPY_NLR_SETJMP
-#include "py/mpstate.h"
-
-NORETURN void nlr_setjmp_jump(void *val);
 // nlr_push() must be defined as a macro, because "The stack context will be
 // invalidated if the function which called setjmp() returns."
-#define nlr_push(buf) ( \
-    (buf)->prev = MP_STATE_THREAD(nlr_top), \
-    MP_NLR_SAVE_PYSTACK(buf), \
-    MP_STATE_THREAD(nlr_top) = (buf), \
-    setjmp((buf)->jmpbuf))
-#define nlr_pop() { MP_STATE_THREAD(nlr_top) = MP_STATE_THREAD(nlr_top)->prev; }
-#define nlr_jump(val) nlr_setjmp_jump(val)
+// For this case it is safe to call nlr_push_tail() first.
+#define nlr_push(buf) (nlr_push_tail(buf), setjmp((buf)->jmpbuf))
 #else
 unsigned int nlr_push(nlr_buf_t *);
+#endif
+
+unsigned int nlr_push_tail(nlr_buf_t *top);
 void nlr_pop(void);
 NORETURN void nlr_jump(void *val);
-#endif
+NORETURN void nlr_jump_tail(nlr_buf_t *top);
 
 // This must be implemented by a port.  It's called by nlr_jump
 // if no nlr buf has been pushed.  It must not return, but rather
@@ -123,7 +121,6 @@ NORETURN void nlr_jump_fail(void *val);
 /*
 #define nlr_push(val) \
     printf("nlr_push: before: nlr_top=%p, val=%p\n", MP_STATE_THREAD(nlr_top), val),assert(MP_STATE_THREAD(nlr_top) != val),nlr_push(val)
-#endif
 */
 #endif
 
diff --git a/py/nlrsetjmp.c b/py/nlrsetjmp.c
index 63376a5537..6ddad37934 100644
--- a/py/nlrsetjmp.c
+++ b/py/nlrsetjmp.c
@@ -28,15 +28,7 @@
 
 #if MICROPY_NLR_SETJMP
 
-void nlr_setjmp_jump(void *val) {
-    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
-    nlr_buf_t *top = *top_ptr;
-    if (top == NULL) {
-        nlr_jump_fail(val);
-    }
-    top->ret_val = val;
-    MP_NLR_RESTORE_PYSTACK(top);
-    *top_ptr = top->prev;
+NORETURN void nlr_jump_tail(nlr_buf_t *top) {
     longjmp(top->jmpbuf, 1);
 }
 
diff --git a/py/nlrthumb.c b/py/nlrthumb.c
index eab5759f21..4edd1456dd 100644
--- a/py/nlrthumb.c
+++ b/py/nlrthumb.c
@@ -26,7 +26,7 @@
 
 #include "py/mpstate.h"
 
-#if (!defined(MICROPY_NLR_SETJMP) || !MICROPY_NLR_SETJMP) && (defined(__thumb2__) || defined(__thumb__) || defined(__arm__))
+#if MICROPY_NLR_THUMB
 
 #undef nlr_push
 
@@ -37,7 +37,6 @@
 //      r4-r11, r13=sp
 
 __attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) {
-
     __asm volatile (
     "str    r4, [r0, #12]       \n" // store r4 into nlr_buf
     "str    r5, [r0, #16]       \n" // store r5 into nlr_buf
@@ -75,36 +74,10 @@ __attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) {
     "b      nlr_push_tail       \n" // do the rest in C
 #endif
     );
-
-    return 0; // needed to silence compiler warning
 }
 
-__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    nlr->prev = *top;
-    MP_NLR_SAVE_PYSTACK(nlr);
-    *top = nlr;
-    return 0; // normal return
-}
-
-void nlr_pop(void) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    *top = (*top)->prev;
-}
-
-NORETURN __attribute__((naked)) void nlr_jump(void *val) {
-    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
-    nlr_buf_t *top = *top_ptr;
-    if (top == NULL) {
-        nlr_jump_fail(val);
-    }
-
-    top->ret_val = val;
-    MP_NLR_RESTORE_PYSTACK(top);
-    *top_ptr = top->prev;
-
+NORETURN __attribute__((naked)) void nlr_jump_tail(nlr_buf_t *top) {
     __asm volatile (
-    "mov    r0, %0              \n" // r0 points to nlr_buf
     "ldr    r4, [r0, #12]       \n" // load r4 from nlr_buf
     "ldr    r5, [r0, #16]       \n" // load r5 from nlr_buf
     "ldr    r6, [r0, #20]       \n" // load r6 from nlr_buf
@@ -133,12 +106,7 @@ NORETURN __attribute__((naked)) void nlr_jump(void *val) {
 #endif
     "movs   r0, #1              \n" // return 1, non-local return
     "bx     lr                  \n" // return
-    :                               // output operands
-    : "r"(top)                      // input operands
-    :                               // clobbered registers
     );
-
-    for (;;); // needed to silence compiler warning
 }
 
-#endif // (!defined(MICROPY_NLR_SETJMP) || !MICROPY_NLR_SETJMP) && (defined(__thumb2__) || defined(__thumb__) || defined(__arm__))
+#endif // MICROPY_NLR_THUMB
diff --git a/py/nlrx64.c b/py/nlrx64.c
index ddcd761665..e7e2e14748 100644
--- a/py/nlrx64.c
+++ b/py/nlrx64.c
@@ -26,7 +26,7 @@
 
 #include "py/mpstate.h"
 
-#if !MICROPY_NLR_SETJMP && defined(__x86_64__)
+#if MICROPY_NLR_X64
 
 #undef nlr_push
 
@@ -39,8 +39,6 @@
 #define NLR_OS_WINDOWS 0
 #endif
 
-__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr);
-
 unsigned int nlr_push(nlr_buf_t *nlr) {
     (void)nlr;
 
@@ -88,54 +86,38 @@ unsigned int nlr_push(nlr_buf_t *nlr) {
     return 0; // needed to silence compiler warning
 }
 
-__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    nlr->prev = *top;
-    MP_NLR_SAVE_PYSTACK(nlr);
-    *top = nlr;
-    return 0; // normal return
-}
-
-void nlr_pop(void) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    *top = (*top)->prev;
-}
-
-NORETURN void nlr_jump(void *val) {
-    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
-    nlr_buf_t *top = *top_ptr;
-    if (top == NULL) {
-        nlr_jump_fail(val);
-    }
-
-    top->ret_val = val;
-    MP_NLR_RESTORE_PYSTACK(top);
-    *top_ptr = top->prev;
+NORETURN void nlr_jump_tail(nlr_buf_t *top) {
+    (void)top;
 
     __asm volatile (
-    "movq   %0, %%rcx           \n" // %rcx points to nlr_buf
     #if NLR_OS_WINDOWS
-    "movq   88(%%rcx), %%rsi    \n" // load saved %rsi
-    "movq   80(%%rcx), %%rdi    \n" // load saved %rdr
+    "movq   88(%rcx), %rsi      \n" // load saved %rsi
+    "movq   80(%rcx), %rdi      \n" // load saved %rdr
+    "movq   72(%rcx), %r15      \n" // load saved %r15
+    "movq   64(%rcx), %r14      \n" // load saved %r14
+    "movq   56(%rcx), %r13      \n" // load saved %r13
+    "movq   48(%rcx), %r12      \n" // load saved %r12
+    "movq   40(%rcx), %rbx      \n" // load saved %rbx
+    "movq   32(%rcx), %rsp      \n" // load saved %rsp
+    "movq   24(%rcx), %rbp      \n" // load saved %rbp
+    "movq   16(%rcx), %rax      \n" // load saved %rip
+    #else
+    "movq   72(%rdi), %r15      \n" // load saved %r15
+    "movq   64(%rdi), %r14      \n" // load saved %r14
+    "movq   56(%rdi), %r13      \n" // load saved %r13
+    "movq   48(%rdi), %r12      \n" // load saved %r12
+    "movq   40(%rdi), %rbx      \n" // load saved %rbx
+    "movq   32(%rdi), %rsp      \n" // load saved %rsp
+    "movq   24(%rdi), %rbp      \n" // load saved %rbp
+    "movq   16(%rdi), %rax      \n" // load saved %rip
     #endif
-    "movq   72(%%rcx), %%r15    \n" // load saved %r15
-    "movq   64(%%rcx), %%r14    \n" // load saved %r14
-    "movq   56(%%rcx), %%r13    \n" // load saved %r13
-    "movq   48(%%rcx), %%r12    \n" // load saved %r12
-    "movq   40(%%rcx), %%rbx    \n" // load saved %rbx
-    "movq   32(%%rcx), %%rsp    \n" // load saved %rsp
-    "movq   24(%%rcx), %%rbp    \n" // load saved %rbp
-    "movq   16(%%rcx), %%rax    \n" // load saved %rip
-    "movq   %%rax, (%%rsp)      \n" // store saved %rip to stack
-    "xorq   %%rax, %%rax        \n" // clear return register
-    "inc    %%al                \n" // increase to make 1, non-local return
+    "movq   %rax, (%rsp)        \n" // store saved %rip to stack
+    "xorq   %rax, %rax          \n" // clear return register
+    "inc    %al                 \n" // increase to make 1, non-local return
     "ret                        \n" // return
-    :                               // output operands
-    : "r"(top)                      // input operands
-    :                               // clobbered registers
     );
 
     for (;;); // needed to silence compiler warning
 }
 
-#endif // !MICROPY_NLR_SETJMP && defined(__x86_64__)
+#endif // MICROPY_NLR_X64
diff --git a/py/nlrx86.c b/py/nlrx86.c
index 3a27460eb6..cc37f72afb 100644
--- a/py/nlrx86.c
+++ b/py/nlrx86.c
@@ -26,25 +26,13 @@
 
 #include "py/mpstate.h"
 
-#if !MICROPY_NLR_SETJMP && defined(__i386__)
+#if MICROPY_NLR_X86
 
 #undef nlr_push
 
 // For reference, x86 callee save regs are:
 //  ebx, esi, edi, ebp, esp, eip
 
-#if defined(_WIN32) || defined(__CYGWIN__)
-#define NLR_OS_WINDOWS 1
-#else
-#define NLR_OS_WINDOWS 0
-#endif
-
-#if NLR_OS_WINDOWS
-unsigned int nlr_push_tail(nlr_buf_t *nlr) asm("nlr_push_tail");
-#else
-__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr);
-#endif
-
 unsigned int nlr_push(nlr_buf_t *nlr) {
     (void)nlr;
 
@@ -70,48 +58,23 @@ unsigned int nlr_push(nlr_buf_t *nlr) {
     return 0; // needed to silence compiler warning
 }
 
-__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    nlr->prev = *top;
-    MP_NLR_SAVE_PYSTACK(nlr);
-    *top = nlr;
-    return 0; // normal return
-}
-
-void nlr_pop(void) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    *top = (*top)->prev;
-}
-
-NORETURN void nlr_jump(void *val) {
-    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
-    nlr_buf_t *top = *top_ptr;
-    if (top == NULL) {
-        nlr_jump_fail(val);
-    }
-
-    top->ret_val = val;
-    MP_NLR_RESTORE_PYSTACK(top);
-    *top_ptr = top->prev;
+NORETURN void nlr_jump_tail(nlr_buf_t *top) {
+    (void)top;
 
     __asm volatile (
-    "mov    %0, %%edx           \n" // %edx points to nlr_buf
-    "mov    28(%%edx), %%esi    \n" // load saved %esi
-    "mov    24(%%edx), %%edi    \n" // load saved %edi
-    "mov    20(%%edx), %%ebx    \n" // load saved %ebx
-    "mov    16(%%edx), %%esp    \n" // load saved %esp
-    "mov    12(%%edx), %%ebp    \n" // load saved %ebp
-    "mov    8(%%edx), %%eax     \n" // load saved %eip
-    "mov    %%eax, (%%esp)      \n" // store saved %eip to stack
-    "xor    %%eax, %%eax        \n" // clear return register
-    "inc    %%al                \n" // increase to make 1, non-local return
+    "mov    28(%edx), %esi      \n" // load saved %esi
+    "mov    24(%edx), %edi      \n" // load saved %edi
+    "mov    20(%edx), %ebx      \n" // load saved %ebx
+    "mov    16(%edx), %esp      \n" // load saved %esp
+    "mov    12(%edx), %ebp      \n" // load saved %ebp
+    "mov    8(%edx), %eax       \n" // load saved %eip
+    "mov    %eax, (%esp)        \n" // store saved %eip to stack
+    "xor    %eax, %eax          \n" // clear return register
+    "inc    %al                 \n" // increase to make 1, non-local return
     "ret                        \n" // return
-    :                               // output operands
-    : "r"(top)                      // input operands
-    :                               // clobbered registers
     );
 
     for (;;); // needed to silence compiler warning
 }
 
-#endif // !MICROPY_NLR_SETJMP && defined(__i386__)
+#endif // MICROPY_NLR_X86
diff --git a/py/nlrxtensa.c b/py/nlrxtensa.c
index 5a969fc87c..6b99182271 100644
--- a/py/nlrxtensa.c
+++ b/py/nlrxtensa.c
@@ -26,7 +26,7 @@
 
 #include "py/mpstate.h"
 
-#if !MICROPY_NLR_SETJMP && defined(__xtensa__)
+#if MICROPY_NLR_XTENSA
 
 #undef nlr_push
 
@@ -37,6 +37,7 @@
 //  a3-a7 = rest of args
 
 unsigned int nlr_push(nlr_buf_t *nlr) {
+    (void)nlr;
 
     __asm volatile (
     "s32i.n  a0, a2, 8          \n" // save regs...
@@ -55,32 +56,10 @@ unsigned int nlr_push(nlr_buf_t *nlr) {
     return 0; // needed to silence compiler warning
 }
 
-__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    nlr->prev = *top;
-    MP_NLR_SAVE_PYSTACK(nlr);
-    *top = nlr;
-    return 0; // normal return
-}
-
-void nlr_pop(void) {
-    nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
-    *top = (*top)->prev;
-}
-
-NORETURN void nlr_jump(void *val) {
-    nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
-    nlr_buf_t *top = *top_ptr;
-    if (top == NULL) {
-        nlr_jump_fail(val);
-    }
-
-    top->ret_val = val;
-    MP_NLR_RESTORE_PYSTACK(top);
-    *top_ptr = top->prev;
+NORETURN void nlr_jump_tail(nlr_buf_t *top) {
+    (void)top;
 
     __asm volatile (
-    "mov.n   a2, %0             \n" // a2 points to nlr_buf
     "l32i.n  a0, a2, 8          \n" // restore regs...
     "l32i.n  a1, a2, 12         \n"
     "l32i.n  a8, a2, 16         \n"
@@ -93,12 +72,9 @@ NORETURN void nlr_jump(void *val) {
     "l32i.n  a15, a2, 44        \n"
     "movi.n a2, 1               \n" // return 1, non-local return
     "ret.n                      \n" // return
-    :                               // output operands
-    : "r"(top)                      // input operands
-    :                               // clobbered registers
     );
 
     for (;;); // needed to silence compiler warning
 }
 
-#endif // !MICROPY_NLR_SETJMP && defined(__xtensa__)
+#endif // MICROPY_NLR_XTENSA
diff --git a/py/py.mk b/py/py.mk
index 0b5d5f8c40..de82a971bc 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -103,6 +103,7 @@ endif
 # py object files
 PY_O_BASENAME = \
 	mpstate.o \
+	nlr.o \
 	nlrx86.o \
 	nlrx64.o \
 	nlrthumb.o \