Add overrides for llvm.copysign.{f32,f64}
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robdockins
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Sep 15, 2021
robdockins
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Sep 15, 2021
LLVM 12 is much more eager to simplify certain expressions to calls to `llvm.copysign.f*`, as illustrated in #187 (comment). It proves relatively straightforward to just add overrides for the `llvm.copysign.f{32,64}` instrinsics, so this patch accomplishes just that. The one caveat is that we cannot accurately represent the semantics of `llvm.copysign.f*` with respect to NaN arguments, since What4 does not possess a way to distinguish the sign bits of NaN values. I decided not to let perfect be the enemy of good, however, so I simply made a note of this limitation in the `crucible-llvm/doc/limitations.md` file. Addresses one bullet point in #187.
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The former has effectively replaced the latter, so hopefully using the more up-to-date one will reduce flakiness when downloading GHC.
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LLVM 12 is much more eager to simplify certain expressions to calls to
llvm.copysign.f*, as illustrated in #187 (comment). It proves relatively straightforward to just add overrides for thellvm.copysign.f{32,64}instrinsics, so this patch accomplishes just that. The one caveat is that we cannot accurately represent the semantics ofllvm.copysign.f*with respect to NaN arguments, since What4 does not possess a way to distinguish the sign bits of NaN values. I decided not to let perfect be the enemy of good, however, so I simply made a note of this limitation in thecrucible-llvm/doc/limitations.mdfile.Addresses one bullet point in #187.