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VarAction2: Infer that unsigned mod 2 results in 0 or 1

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This commit is contained in:
Jonathan G Rennison 2022-08-18 19:24:01 +01:00
parent ad00f5032a
commit b04d1295cd
1 changed files with 6 additions and 0 deletions
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6
src/newgrf_optimiser.cpp
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@ -1003,6 +1003,12 @@ void OptimiseVarAction2Adjust(VarAction2OptimiseState &state, const GrfSpecFeatu
group->dsg_flags |= DSGF_CHECK_INSERT_JUMP; group->dsg_flags |= DSGF_CHECK_INSERT_JUMP;
} }
} }
if (adjust.operation == DSGA_OP_RST && adjust.type == DSGA_TYPE_MOD && adjust.divmod_val == 2) {
/* Non-negative value % 2 implies VA2AIF_ONE_OR_ZERO */
if ((uint64)adjust.and_mask + (uint64)adjust.add_val < (uint64)get_sign_bit()) {
state.inference |= VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
}
}
} else { } else {
if (adjust.and_mask == 0 && IsEvalAdjustWithZeroRemovable(adjust.operation)) { if (adjust.and_mask == 0 && IsEvalAdjustWithZeroRemovable(adjust.operation)) {
/* Delete useless zero operations */ /* Delete useless zero operations */