py: Support arm and thumb ARM ISAs, in addition to thumb2.

These changes were tested with QEMU, and by few people of real hardware.

py/nlr.h

@@ -45,7 +45,7 @@ struct _nlr_buf_t {
   #else
     void *regs[8];
   #endif
-#elif defined(__thumb2__)
+#elif defined(__thumb2__) || defined(__thumb__) || defined(__arm__)
     void *regs[10];
 #else
     #define MICROPY_NLR_SETJMP (1)

py/nlrthumb.S

@@ -24,19 +24,21 @@
  * THE SOFTWARE.
  */
 
-#if defined(__thumb2__) && !MICROPY_NLR_SETJMP
+#if !MICROPY_NLR_SETJMP && (defined(__thumb2__) || defined(__thumb__) || defined(__arm__))
-/* thumb callee save: bx, bp, sp, r12, r14, r14, r15 */
+/* arm callee save: bx, bp, sp, r12, r14, r14, r15 */
 
     .syntax unified
     /*.cpu cortex-m4*/
-    .thumb
+    /*.thumb*/
     .text
     .align  2
 
 /* uint nlr_push(r0=nlr_buf_t *nlr) */
     .global nlr_push
+#if defined(__thumb2__)
     .thumb
     .thumb_func
+#endif
     .type   nlr_push, %function
 nlr_push:
     str     lr, [r0, #8]            @ store lr into nlr_buf
@@ -64,8 +66,10 @@ nlr_push:
 
 @ void nlr_pop()
     .global nlr_pop
+#if defined(__thumb2__)
     .thumb
     .thumb_func
+#endif
     .type   nlr_pop, %function
 nlr_pop:
     ldr     r3, .L5                 @ load addr of nlr_top
@@ -80,8 +84,10 @@ nlr_pop:
 
 /* void nlr_jump(r0=uint val) */
     .global nlr_jump
+#if defined(__thumb2__)
     .thumb
     .thumb_func
+#endif
     .type   nlr_jump, %function
 nlr_jump:
     ldr     r3, .L2                 @ load addr of nlr_top

unix/gccollect.c

@@ -97,7 +97,7 @@ void gc_helper_get_regs(regs_t arr) {
 }
 #endif
 
-#ifdef __thumb2__
+#if defined(__thumb2__) || defined(__thumb__) || defined(__arm__)
 typedef machine_uint_t regs_t[10];
 
 void gc_helper_get_regs(regs_t arr) {