1 files changed, 96 insertions, 0 deletions
diff --git a/deps/lightning/doc/rpn.c b/deps/lightning/doc/rpn.c
new file mode 100644
index 0000000..8131484
--- /dev/null
+++ b/deps/lightning/doc/rpn.c
@@ -0,0 +1,96 @@
+#include <stdio.h>
+#include <lightning.h>
+
+typedef int (*pifi)(int);       /* Pointer to Int Function of Int */
+
+static jit_state_t *_jit;
+
+void stack_push(int reg, int *sp)
+{
+  jit_stxi_i (*sp, JIT_FP, reg);
+  *sp += sizeof (int);
+}
+
+void stack_pop(int reg, int *sp)
+{
+  *sp -= sizeof (int);
+  jit_ldxi_i (reg, JIT_FP, *sp);
+}
+
+jit_node_t *compile_rpn(char *expr)
+{
+  jit_node_t *in, *fn;
+  int stack_base, stack_ptr;
+
+  fn = jit_note(NULL, 0);
+  jit_prolog();
+  in = jit_arg();
+  stack_ptr = stack_base = jit_allocai (32 * sizeof (int));
+
+  jit_getarg_i(JIT_R2, in);
+
+  while (*expr) {
+    char buf[32];
+    int n;
+    if (sscanf(expr, "%[0-9]%n", buf, &n)) {
+      expr += n - 1;
+      stack_push(JIT_R0, &stack_ptr);
+      jit_movi(JIT_R0, atoi(buf));
+    } else if (*expr == 'x') {
+      stack_push(JIT_R0, &stack_ptr);
+      jit_movr(JIT_R0, JIT_R2);
+    } else if (*expr == '+') {
+      stack_pop(JIT_R1, &stack_ptr);
+      jit_addr(JIT_R0, JIT_R1, JIT_R0);
+    } else if (*expr == '-') {
+      stack_pop(JIT_R1, &stack_ptr);
+      jit_subr(JIT_R0, JIT_R1, JIT_R0);
+    } else if (*expr == '*') {
+      stack_pop(JIT_R1, &stack_ptr);
+      jit_mulr(JIT_R0, JIT_R1, JIT_R0);
+    } else if (*expr == '/') {
+      stack_pop(JIT_R1, &stack_ptr);
+      jit_divr(JIT_R0, JIT_R1, JIT_R0);
+    } else {
+      fprintf(stderr, "cannot compile: %s\n", expr);
+      abort();
+    }
+    ++expr;
+  }
+  jit_retr(JIT_R0);
+  jit_epilog();
+  return fn;
+}
+
+int main(int argc, char *argv[])
+{
+  jit_node_t *nc, *nf;
+  pifi c2f, f2c;
+  int i;
+
+  init_jit(argv[0]);
+  _jit = jit_new_state();
+
+  nc = compile_rpn("32x9*5/+");
+  nf = compile_rpn("x32-5*9/");
+  (void)jit_emit();
+  c2f = (pifi)jit_address(nc);
+  f2c = (pifi)jit_address(nf);
+  jit_clear_state();
+
+  printf("\nC:");
+  for (i = 0; i <= 100; i += 10) printf("%3d ", i);
+  printf("\nF:");
+  for (i = 0; i <= 100; i += 10) printf("%3d ", c2f(i));
+  printf("\n");
+
+  printf("\nF:");
+  for (i = 32; i <= 212; i += 18) printf("%3d ", i);
+  printf("\nC:");
+  for (i = 32; i <= 212; i += 18) printf("%3d ", f2c(i));
+  printf("\n");
+
+  jit_destroy_state();
+  finish_jit();
+  return 0;
+}