py: Modify bytecode "with" behaviour so it doesn't use any heap.

Before this patch a "with" block needed to create a bound method object
on the heap for the __exit__ call.  Now it doesn't because we use
load_method instead of load_attr, and save the method+self on the stack.

1 files changed, 5 insertions, 2 deletions

diff --git a/py/emitbc.c b/py/emitbc.c
index 8d482afe52..b9304fd82d 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -680,12 +680,15 @@ void mp_emit_bc_unwind_jump(emit_t *emit, mp_uint_t label, mp_uint_t except_dept
 }
 
 void mp_emit_bc_setup_with(emit_t *emit, mp_uint_t label) {
-    emit_bc_pre(emit, 7);
+    // TODO We can probably optimise the amount of needed stack space, since
+    // we don't actually need 4 slots during the entire with block, only in
+    // the cleanup handler in certain cases.  It needs some thinking.
+    emit_bc_pre(emit, 4);
     emit_write_bytecode_byte_unsigned_label(emit, MP_BC_SETUP_WITH, label);
 }
 
 void mp_emit_bc_with_cleanup(emit_t *emit) {
-    emit_bc_pre(emit, -7);
+    emit_bc_pre(emit, -4);
     emit_write_bytecode_byte(emit, MP_BC_WITH_CLEANUP);
 }