[HandshakeOptimizeBitwidths] Fix forward logic for shrui#812
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The previous logic for `shrui` for the forward pass did not properly handle sign-extension for `shrui`, resulting in sign-extension of the result often being performed in cases where the shifting should fill in 0 bits. Furthermore, if the constant was larger than the minimal input bitwidth, integer overflow would occur in the implementation causing crashes. This PR fixes that issue by splitting the forward pass for `shrui` out of the common shift pattern and taking both zero-extension and sign-extension of the input into account. I believe the logic of `shrui` and `shrsi` to likely be different enough to require different forwarding patterns. The older generic `ArithShift` pattern remains in use for the backward pass. Fixes #792
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The previous logic for `shrsi` for the forward pass often crashed in edge cases such as the shift amount was larger than the bitwidth. This PR rewrites the forward logic for `shrsi` into a dedicated pattern. In the case of the input of `shrsi` being zero-extended we just optimize it to a `shrui` and reuse the existing optimization logic there. Fixes #792 Depends on #812
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The previous logic for
shruifor the forward pass did not properly handle sign-extension forshrui, resulting in sign-extension of the result often being performed in cases where the shifting should fill in 0 bits. Furthermore, if the constant was larger than the minimal input bitwidth, integer overflow would occur in the implementation causing crashes.This PR fixes that issue by splitting the forward pass for
shruiout of the common shift pattern and taking both zero-extension and sign-extension of the input into account. I believe the logic ofshruiandshrsito likely be different enough to require different forwarding patterns. The older genericArithShiftpattern remains in use for the backward pass.Fixes #792
Depends on #802 to function