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author | Björn Gustavsson <[email protected]> | 2019-02-04 10:03:55 +0100 |
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committer | Björn Gustavsson <[email protected]> | 2019-02-11 06:36:12 +0100 |
commit | 4763811e1d67a0d2ac3442d4694b4e1dee1b4364 (patch) | |
tree | 99e059b0a795e1d4716743c48a63742f0ad4a7bc /bootstrap/lib | |
parent | 3542afbdc4909455ad9e45e2b5328835a838a1bd (diff) | |
download | otp-4763811e1d67a0d2ac3442d4694b4e1dee1b4364.tar.gz otp-4763811e1d67a0d2ac3442d4694b4e1dee1b4364.tar.bz2 otp-4763811e1d67a0d2ac3442d4694b4e1dee1b4364.zip |
beam_ssa_type: Propagate the 'none' type from calls
Consider this pseudo code:
f(...) ->
Val = case Expr of
... ->
... ;
... ->
... ;
... ->
my_abort(something_went_wrong)
end,
%% Here follows code that uses Val.
.
.
.
my_abort(Reason) ->
throw({error,Reason}).
The first two clauses in the case will probably provide some
information about the type of the variable `Var`, information
that would be useful for optimizing the code that follows the
case.
However, the third clause would ruin everything. The call
to `my_abort/1` could return anything, and thus `Val` could
also have any type.
294d66a295f6 introduced module-level type analysis, which will in
general keep track of the return type of a local function
call. However, it does not improve the optimization for this specific
function. When a function never returns, that is, when its type is
`none`, it does not propagate the `none` type, but instead pretends
that the return type is `any`.
This commit extends the handling of functions that don't return to
properly handle the `none` type. Any instructions that directly
follows the function that does not return will be discarded, and the
call will be rewritten to a tail-recursive call.
For this specific example, it means that the type for `Val` deduced
from the first two clauses will be retained and can be used for
optimizing the code after the case.
Diffstat (limited to 'bootstrap/lib')
0 files changed, 0 insertions, 0 deletions