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py/emit: Suppress unreachable bytecode/native code that follows jump.

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This new logic tracks when an unconditional jump/raise occurs in the
emitted code stream (bytecode or native machine code) and suppresses all
subsequent code, until a label is assigned.  This eliminates a lot of
cases of dead code, with relatively simple logic.

This commit combined with the previous one (that removed the existing
dead-code finding logic) has the following code size change:

       bare-arm:   -16 -0.028%
    minimal x86:   -60 -0.036%
       unix x64:  -368 -0.070%
    unix nanbox:   -80 -0.017%
          stm32:  -204 -0.052% PYBV10
         cc3200:    +0 +0.000%
        esp8266:  -232 -0.033% GENERIC
          esp32:  -224 -0.015% GENERIC[incl -40(data)]
         mimxrt:  -192 -0.054% TEENSY40
     renesas-ra:  -200 -0.032% RA6M2_EK
            nrf:   +28 +0.015% pca10040
            rp2:  -256 -0.050% PICO
           samd:   -12 -0.009% ADAFRUIT_ITSYBITSY_M4_EXPRESS

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George
2022-06-17 23:14:32 +10:00
parent e85a096302
commit a506335524
8 changed files with 268 additions and 66 deletions
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2
py/emitnative.c
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@@ -1966,6 +1966,7 @@ STATIC void emit_native_jump(emit_t *emit, mp_uint_t label) {
need_stack_settled(emit);
ASM_JUMP(emit->as, label);
emit_post(emit);
mp_asm_base_suppress_code(&emit->as->base);
}
STATIC void emit_native_jump_helper(emit_t *emit, bool cond, mp_uint_t label, bool pop) {
@@ -2810,6 +2811,7 @@ STATIC void emit_native_raise_varargs(emit_t *emit, mp_uint_t n_args) {
}
// TODO probably make this 1 call to the runtime (which could even call convert, native_raise(obj, type))
emit_call(emit, MP_F_NATIVE_RAISE);
mp_asm_base_suppress_code(&emit->as->base);
}
STATIC void emit_native_yield(emit_t *emit, int kind) {