[issue4753] Faster opcode dispatch on gcc

[Paolo 'Blaisorblade' Giarrusso]

Paolo 'Blaisorblade' Giarrusso <p.giarrusso at gmail.com> added the comment:

== On the patch itself ==
Why don't you use the C preprocessor instead of that Python code?
Sample code:

#define OPCODE_LIST(DEFINE_OPCODE) \
    DEFINE_OPCODE(STOP_CODE, 0)                 \
    DEFINE_OPCODE(POP_TOP, 1)                   \
    DEFINE_OPCODE(ROT_TWO, 2)                   \
    DEFINE_OPCODE(ROT_THREE, 3)                 \
    DEFINE_OPCODE(DUP_TOP, 4)                   \
    DEFINE_OPCODE(ROT_FOUR, 5)                  \
    DEFINE_OPCODE(NOP, 9)                       \
    ...

# define DECL_OPCODE(opcode)                    \
        [opcode] = && label_ ## opcode,

        void *opcodes[] = {
                OPCODE_LIST(DECL_OPCODE)
        };
# undef DECL_OPCODE

There are also other ways to do it, but using higher-order functions
within the preprocessor in this way is something that I learned from the
V8 source code.
It has the advantage that OPCODE_LIST can be used in a lot of other
places (maybe when implementing the 'opcode' module, if it's written in C).

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<http://bugs.python.org/issue4753>
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