Flambda optimizes away code that raises Division_by_zero

[vicuna]

Original bug ID: 7328
Reporter: @yallop
Assigned to: @chambart
Status: closed (set by @damiendoligez on 2016-10-26T15:03:00Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 4.04.0 +dev / +beta1 / +beta2
Target version: 4.05.0 +dev/beta1/beta2/beta3/rc1
Fixed in version: 4.05.0 +dev/beta1/beta2/beta3/rc1
Category: middle end (typedtree to clambda)

Bug description

Example:

$ cat div.ml
let _ = Int64.div 1L 0L in print_endline "done"

With flambda:

$ opam switch 4.04.0+beta1+flambda
# To setup the new switch in the current shell, you need to run:
eval `opam config env`
$ eval `opam config env`
$ ocamlopt div.ml && ./a.out
done

Without flambda:

$ opam switch 4.04.0+beta1
# To setup the new switch in the current shell, you need to run:
eval `opam config env`
$ eval `opam config env`
$ ocamlopt div.ml && ./a.out
Fatal error: exception Division_by_zero

[vicuna]

Comment author: @chambart

Pdivbint and Pmodbint are marked as 'No_effects' by Semantics_of_primitives.

I will add the fix to #702 as this needs the same handling.