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Simplify softfloat interface #289

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wants to merge 2 commits into from
Closed

Simplify softfloat interface #289

wants to merge 2 commits into from

Commits on Aug 5, 2023

  1. Simplify softfloat interface 

    Currently the softfloat interface relies on two global registers defined in Sail to return values, one of which is a mirror of `fflags`. Unfortunately this doesn't work if the model is compiled with `-static` or wrapped in an anonymous namespace (I am doing the latter in a similar way to [@arichardson's method here](https://github.com/CTSRD-CHERI/cheri-compressed-cap/blob/89d21384c0183e5c422e23e1e5b37e127ad14e96/test/sail_wrapper_common.c#L50)).

This commit changes the design so that there is only a one-way dependency - the softfloat implementation does not depend on the model. This is done by returning the result of the floating point operation as a normal function return value, and then the model retrieves the new flags by simply calling another platform function (`extern_float_flags()`).

This is a bit cleaner, works with `-static` and also removes the need for `write_fflags()` and `update_softfloat_fflags()`.

Tested with `run_fp_tests.sh` - all 82 tests pass.

This commit only applies the changes to f16add/sub/mul/div to make review easier.
    @Timmmm
    Timmmm committed Aug 5, 2023
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  2. Apply softfloat simplification to remaining methods 

    Copy/paste the changes in the previous commit to all softfloat methods.
    @Timmmm
    Timmmm committed Aug 5, 2023
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