On Sun, Jun 27, 2021 at 7:57 PM xie cui <cuiwei...@gmail.com> wrote:
>
> a defer call generate some code like:
>
> v42 (8) = StaticLECall <mem> {AuxCall{runtime.deferprocStack}} [8] v36 v41
> v43 (8) = SelectN <mem> [0] v42
>
> Defer v42 → b2 b3 (likely) (8)
>
> b2: ← b1-
>
> v48 (7) = Copy <mem> v43
> v49 (7) = VarKill <mem> {.autotmp_0} v48
> v50 (9) = StaticLECall <mem> {AuxCall{runtime.deferreturn}} v49
> v51 (9) = SelectN <mem> [0] v50
> v52 (9) = MakeResult <mem> v51
>
> Ret v52 (9)
>
> b3: ← b1-
>
> v44 (8) = Copy <mem> v43
> v45 (8) = StaticLECall <mem> {AuxCall{runtime.deferreturn}} v44
> v46 (8) = SelectN <mem> [0] v45
> v47 (8) = MakeResult <mem> v46
>
> Ret v47 (8)
>
> my question is Under what circumstances the deferprocStack return 1?
> some useful info：
> https://github.com/golang/go/blob/master/src/cmd/compile/internal/amd64/ssa.go#L1287-L1289
>
> https://github.com/golang/go/blob/master/src/runtime/panic.go#L290-L328, in
> these lines it seems deferprocStack always return 0. i think i have miss some
> thing, please help me to find when it get to branch return 1.
deferprocStack will appear to return 1 if the deferred function calls
recover. This is implemented by the function "recovery" in
runtime/panic.go, which resets the program counter and stack pointer
and sets the return register to 1.
Ian
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