Anything that produces a hlfir.expr should have an allocation side
effect so that it is not removed by CSE (which would result in two
hlfir.destroy operations for the same expression). Similarly for
hlfir.associate, which has hlfir.end_associate.
Also adds read effects on arguments which are pointer-like or boxes.
I see no regressions from this change when running llvm-testsuite with
optimization enabled, or from SPEC2017 rate benchmarks.
To test this, I have added MLIR's pass for testing side effect
interfaces to fir-opt.
Differential Revision: https://reviews.llvm.org/D158662
43d729dda4