py: Optimise generated code for working out line numbers.

py/emitbc.c

@@ -71,10 +71,14 @@ static void emit_write_code_info_qstr(emit_t* emit, qstr qstr) {
     c[3] = (qstr >> 24) & 0xff;
 }
 
-static void emit_write_code_info_byte_byte(emit_t* emit, byte b1, uint b2) {
-    byte* c = emit_get_cur_to_write_code_info(emit, 2);
-    c[0] = b1;
-    c[1] = b2;
+static void emit_write_code_info_bytes_lines(emit_t* emit, uint bytes_to_skip, uint lines_to_skip) {
+    for (; bytes_to_skip > 31; bytes_to_skip -= 31) {
+        *emit_get_cur_to_write_code_info(emit, 1) = 31;
+    }
+    for (; lines_to_skip > 7; lines_to_skip -= 7) {
+        *emit_get_cur_to_write_code_info(emit, 1) = 7 << 5;
+    }
+    *emit_get_cur_to_write_code_info(emit, 1) = bytes_to_skip | (lines_to_skip << 5);
 }
 
 // all functions must go through this one to emit byte code
@@ -218,7 +222,7 @@ static void emit_bc_end_pass(emit_t *emit) {
         printf("ERROR: stack size not back to zero; got %d\n", emit->stack_size);
     }
 
-    emit_write_code_info_byte_byte(emit, 0, 0); // end of line number info
+    emit_write_code_info_bytes_lines(emit, 0, 0); // end of line number info
 
     if (emit->pass == PASS_2) {
         // calculate size of code in bytes
@@ -246,15 +250,9 @@ static void emit_bc_set_stack_size(emit_t *emit, int size) {
 static void emit_bc_set_source_line(emit_t *emit, int source_line) {
     //printf("source: line %d -> %d  offset %d -> %d\n", emit->last_source_line, source_line, emit->last_source_line_offset, emit->byte_code_offset);
     if (source_line > emit->last_source_line) {
-        int bytes_to_skip = emit->byte_code_offset - emit->last_source_line_offset;
-        for (; bytes_to_skip > 255; bytes_to_skip -= 255) {
-            emit_write_code_info_byte_byte(emit, 255, 0);
-        }
-        int lines_to_skip = source_line - emit->last_source_line;
-        for (; lines_to_skip > 255; lines_to_skip -= 255) {
-            emit_write_code_info_byte_byte(emit, 0, 255);
-        }
-        emit_write_code_info_byte_byte(emit, bytes_to_skip, lines_to_skip);
+        uint bytes_to_skip = emit->byte_code_offset - emit->last_source_line_offset;
+        uint lines_to_skip = source_line - emit->last_source_line;
+        emit_write_code_info_bytes_lines(emit, bytes_to_skip, lines_to_skip);
         //printf("  %d %d\n", bytes_to_skip, lines_to_skip);
         emit->last_source_line_offset = emit->byte_code_offset;
         emit->last_source_line = source_line;

py/vm.c

@@ -550,12 +550,9 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
                 machine_uint_t source_line = 1;
                 machine_uint_t bc = save_ip - code_info - code_info_size;
                 //printf("find %lu %d %d\n", bc, code_info[12], code_info[13]);
-                for (const byte* ci = code_info + 12; bc >= ci[0]; ci += 2) {
-                    bc -= ci[0];
-                    source_line += ci[1];
-                    if (ci[0] == 0 && ci[1] == 0) {
-                        break;
-                    }
+                for (const byte* ci = code_info + 12; *ci && bc >= ((*ci) & 31); ci++) {
+                    bc -= *ci & 31;
+                    source_line += *ci >> 5;
                 }
                 mp_obj_exception_add_traceback(nlr.ret_val, source_file, source_line, block_name);
             }