René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Reorder instructions in with/async-with exception handler to reduce the size of the exception table.","articleBody":"The dis for this function:\r\n\r\n```\r\ndef f1(cm):\r\n    with cm:\r\n        x = 1\r\n    x = 2\r\n```\r\n\r\nis this:\r\n\r\n```\r\n 11           0 RESUME                   0\r\n\r\n 12           2 LOAD_FAST                0 (cm)\r\n              4 BEFORE_WITH\r\n              6 POP_TOP\r\n\r\n 13           8 LOAD_CONST               1 (1)\r\n             10 STORE_FAST               1 (x)\r\n\r\n 12          12 LOAD_CONST               0 (None)\r\n             14 LOAD_CONST               0 (None)\r\n             16 LOAD_CONST               0 (None)\r\n             18 CALL                     2\r\n             28 POP_TOP\r\n\r\n 14          30 LOAD_CONST               2 (2)\r\n             32 STORE_FAST               1 (x)\r\n             34 LOAD_CONST               0 (None)\r\n             36 RETURN_VALUE\r\n\r\n 12     \u003e\u003e   38 PUSH_EXC_INFO\r\n             40 WITH_EXCEPT_START\r\n             42 POP_JUMP_FORWARD_IF_TRUE     4 (to 52)\r\n             44 RERAISE                  2\r\n        \u003e\u003e   46 COPY                     3\r\n             48 POP_EXCEPT\r\n             50 RERAISE                  1\r\n        \u003e\u003e   52 POP_TOP\r\n             54 POP_EXCEPT\r\n             56 POP_TOP\r\n             58 POP_TOP\r\n\r\n 14          60 LOAD_CONST               2 (2)\r\n             62 STORE_FAST               1 (x)\r\n             64 LOAD_CONST               0 (None)\r\n             66 RETURN_VALUE\r\nExceptionTable:\r\n  6 to 10 -\u003e 38 [1] lasti\r\n  38 to 44 -\u003e 46 [3] lasti\r\n  52 to 52 -\u003e 46 [3] lasti\r\n```\r\n\r\nNote the last row of the exception table: inst 52 goes to 46, same as  38-44.  We can reorder the code so that this block is consecutive, and we save one entry in the exception table for each with/async with:\r\n\r\n```\r\n 11           0 RESUME                   0\r\n\r\n 12           2 LOAD_FAST                0 (cm)\r\n              4 BEFORE_WITH\r\n              6 POP_TOP\r\n\r\n 13           8 LOAD_CONST               1 (1)\r\n             10 STORE_FAST               1 (x)\r\n\r\n 12          12 LOAD_CONST               0 (None)\r\n             14 LOAD_CONST               0 (None)\r\n             16 LOAD_CONST               0 (None)\r\n             18 CALL                     2\r\n             28 POP_TOP\r\n\r\n 14          30 LOAD_CONST               2 (2)\r\n             32 STORE_FAST               1 (x)\r\n             34 LOAD_CONST               0 (None)\r\n             36 RETURN_VALUE\r\n\r\n 12     \u003e\u003e   38 PUSH_EXC_INFO\r\n             40 WITH_EXCEPT_START\r\n             42 POP_JUMP_FORWARD_IF_TRUE     1 (to 46)\r\n             44 RERAISE                  2\r\n        \u003e\u003e   46 POP_TOP\r\n             48 POP_EXCEPT\r\n             50 POP_TOP\r\n             52 POP_TOP\r\n\r\n 14          54 LOAD_CONST               2 (2)\r\n             56 STORE_FAST               1 (x)\r\n             58 LOAD_CONST               0 (None)\r\n             60 RETURN_VALUE\r\n        \u003e\u003e   62 COPY                     3\r\n             64 POP_EXCEPT\r\n             66 RERAISE                  1\r\nExceptionTable:\r\n  6 to 10 -\u003e 38 [1] lasti\r\n  38 to 46 -\u003e 62 [3] lasti\r\n```","author":{"url":"https://github.com/iritkatriel","@type":"Person","name":"iritkatriel"},"datePublished":"2022-06-08T23:05:46.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/93621/cpython/issues/93621"}