8000 erlc internal consistency error for is_eq_exact · Issue #6183 · erlang/otp · GitHub
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erlc internal consistency error for is_eq_exact #6183

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RobinMorisset opened this issue Jul 29, 2022 · 1 comment · Fixed by #6189
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erlc internal consistency error for is_eq_exact #6183

RobinMorisset opened this issue Jul 29, 2022 · 1 comment · Fixed by #6189
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@RobinMorisset
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On the following code:

-module(is_eq_exact).
-compile([export_all]).

f(V)  when ((V / V) < (V orelse true)); V; V ->
	((V = (a /= V)) orelse 0).

erlc (either built from master as of today including the recent fixes to #6163, #6164, and #6169, or a slightly older version from a few weeks ago) crashes with the following error message:

is_eq_exact:1: function f/1+12:
Internal consistency check failed - please report this bug.
Instruction: {test,is_eq_exact,{f,9},[{x,1},{atom,true}]}
Error: {type_conflict,{t_atom,[true]},{t_atom,[a]}}:
@RobinMorisset RobinMorisset added the bug Issue is reported as a bug label Jul 29, 2022
@bjorng bjorng self-assigned this Jul 31, 2022
bjorng added a commit to bjorng/otp that referenced this issue Aug 1, 2022
@bjorng
Eliminate internal consistency failure
8aa4414 
When attempting to compile the following code:

    foo(V) when (V / V < (V orelse true)); V; V ->
        (V = (a =/= V)) orelse 0.

the `beam_validator` pass produces the following message:

    t:1: function foo/1+12:
      Internal consistency check failed - please report this bug.
      Instruction: {test,is_eq_exact,{f,9},[{x,1},{atom,true}]}
      Error:       {type_conflict,{t_atom,[true]},{t_atom,[a]}}:

The type conflict mentioned refers to the expression `a =/= V`. At
the point of its evaluation, `V` is known to `beam_validator` to be
the atom `true`; thus, evaluation of `a =/= V` is redundant because the
result is always `false`.

The root cause of the problem is that `beam_validator` has a stronger
type analysis for `=/=` expressions than `beam_ssa_type`. By
strengthening the type analysis for `=/=` in `beam_ssa_type`, the
offending redundant tests are removed and `beam_validator` is again
silent.

Fixes erlang#6183
@bjorng bjorng mentioned this issue Aug 1, 2022
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bjorng commented Aug 1, 2022

I have fixed the problem in the linked pull request.

bjorng added a commit to bjorng/otp that referenced this issue Aug 2, 2022
@bjorng
Merge branch 'bjorn/compiler/not-equal/erlangGH-6183' into bjorn/mast…
e1f3a4a 
…er/primary_preloaded

* bjorn/compiler/not-equal/erlangGH-6183:
  Eliminate internal consistency failure
@bjorng bjorng closed this as completed in f05b757 Aug 3, 2022
bjorng added a commit that referenced this issue Aug 3, 2022
@bjorng
Merge pull request #6189 from bjorng/bjorn/compiler/not-equal/GH-6183
f8564a1 
Eliminate internal consistency failure
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Eliminate internal consistency failure bjorng/otp
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