Commits on Mar 25, 2021

1. Handle srem properly when avoid_div_traps is false. …

   The codegen for div/rem ops has two modes, depending on the
   `avoid_div_traps` flag: it can either do all checks for trapping
   conditions explicitly, and use explicit trap instructions, then use a
   hardware divide instruction that will not trap (`avoid_div_traps ==
   true`); or it can run in a mode where a hardware FP fault on the divide
   instruction implies a Wasm trap (`avoid_div_traps == false`). Wasmtime
   uses the former while Lucet (for example) uses the latter.
   
   It turns out that because we run all our spec tests run under Wasmtime,
   we missed a spec corner case that fails in the latter: INT_MIN % -1 == 0
   per the spec, but causes a trap with the x86 signed divide/remainder
   instruction. Hence, in Lucet, this specific remainder computation would
   incorrectly result in a Wasm trap.
   
   This PR fixes the issue by just forcing use of the explicit-checks
   implementation for `srem` even when `avoid_div_traps` is false.

   

   cfallin committed Mar 25, 2021
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