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Proposed patch adds the BUILD_MAP_EX opcode (maybe somebody propose better name?). It takes values from the stack and keys from the tuple on the top of the stack. Currently it affects only creating a dict with const keys and calling a function with keywords after the var-keyword argument.
$ echo "{'a': 1, 'b': 2, 'c': 3}" | ./python -m dis
Unpatched:
 1 0 LOAD_CONST 0 ('a')
 2 LOAD_CONST 1 (1)
 4 LOAD_CONST 2 ('b')
 6 LOAD_CONST 3 (2)
 8 LOAD_CONST 4 ('c')
 10 LOAD_CONST 5 (3)
 12 BUILD_MAP 3
 14 POP_TOP
 16 LOAD_CONST 6 (None)
 18 RETURN_VALUE
Patched:
 1 0 LOAD_CONST 0 (1)
 2 LOAD_CONST 1 (2)
 4 LOAD_CONST 2 (3)
 6 LOAD_CONST 7 (('a', 'b', 'c'))
 8 BUILD_MAP_EX 3
 10 POP_TOP
 12 LOAD_CONST 6 (None)
 14 RETURN_VALUE
$ echo "f(**kw, a=1, b=2, c=3)" | ./python -m dis
Unpatched:
 1 0 LOAD_NAME 0 (f)
 2 LOAD_NAME 1 (kw)
 4 LOAD_CONST 0 ('a')
 6 LOAD_CONST 1 (1)
 8 LOAD_CONST 2 ('b')
 10 LOAD_CONST 3 (2)
 12 LOAD_CONST 4 ('c')
 14 LOAD_CONST 5 (3)
 16 BUILD_MAP 3
 18 EXTENDED_ARG 1
 20 BUILD_MAP_UNPACK_WITH_CALL 258
 22 CALL_FUNCTION_KW 0 (0 positional, 0 keyword pair)
 24 POP_TOP
 26 LOAD_CONST 6 (None)
 28 RETURN_VALUE
Patched:
 1 0 LOAD_NAME 0 (f)
 2 LOAD_NAME 1 (kw)
 4 LOAD_CONST 0 (1)
 6 LOAD_CONST 1 (2)
 8 LOAD_CONST 2 (3)
 10 LOAD_CONST 7 (('a', 'b', 'c'))
 12 BUILD_MAP_EX 3
 14 EXTENDED_ARG 1
 16 BUILD_MAP_UNPACK_WITH_CALL 258
 18 CALL_FUNCTION_KW 0 (0 positional, 0 keyword pair)
 20 POP_TOP
 22 LOAD_CONST 6 (None)
 24 RETURN_VALUE
It could be more useful for new MAKE_FUNCTION opcode (issue27095) and maybe for new CALL_FUNCTION* opcodes.
The benefit of BUILD_MAP_EX is less LOAD_CONST instructions and less stack consuming.