Uday Bondhugula 80610c2f49 Introduce Fourier-Motzkin variable elimination + other cleanup/support ... - Introduce Fourier-Motzkin variable elimination to eliminate a dimension from a system of linear equalities/inequalities. Update isEmpty to use this. Since FM is only exact on rational/real spaces, an emptiness check based on this is guaranteed to be exact whenever it says the underlying set is empty; if it says, it's not empty, there may still be no integer points in it. Also, supports a version that computes "dark shadows". - Test this by checking for "always false" conditionals in if statements. - Unique IntegerSet's that are small (few constraints, few variables). This basically means the canonical empty set and other small sets that are likely commonly used get uniqued; allows checking for the canonical empty set by pointer. IntegerSet::kUniquingThreshold gives the threshold constraint size for uniqui'ing. - rename simplify-affine-expr -> simplify-affine-structures Other cleanup - IntegerSet::numConstraints, AffineMap::numResults are no longer needed; remove them. - add copy assignment operators for AffineMap, IntegerSet. - rename Invalid() -> Null() on AffineExpr, AffineMap, IntegerSet - Misc cleanup for FlatAffineConstraints API PiperOrigin-RevId: 218690456		2019-03-29 13:38:24 -07:00
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mlir-opt.cpp	Introduce Fourier-Motzkin variable elimination + other cleanup/support	2019-03-29 13:38:24 -07:00