MLton 20210117

# RedundantTests

RedundantTests is an optimization pass for the SSA IntermediateLanguage, invoked from SSASimplify.

## Description

This pass simplifies conditionals whose results are implied by a previous conditional test.

## Implementation

- redundant-tests.fun

## Details and Notes

An additional test will sometimes eliminate the overflow test when adding or subtracting 1. In particular, it will eliminate it in the following cases:

    if x < y
      then ... x + 1 ...
    else ... y - 1 ...