[TIR][Arith] Additional Simplifications Inside Conditionals #11524
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Previously, constraints with inequalities were recognized and used for simplifications by `ConstIntBoundAnalyzer` and `ModularSetAnalyzer`, but constraints with equalities were not. This adds equality-based constraints. (e.g. Inside the then-case of `if i==5`, the value of `i` is known to be 5.)
Previously, constraints were only checked within a `tir.likely` annotation. After this change, constraints are used for simplification of all boolean expressions. (e.g. Within a conditional `if i==n`, the expression `(i==n) and (j==m)` can be simplified to `j==m`.)
If a literal constraint relies on the contents of a buffer, the constraint may not be assumed to hold. This prevents the incorrect rewriting of `A[i]==n` to true within a `if A[i]==n` conditional, as the value of `A[i]` may have changed.
Inside a constraint `if i==n and j==m`, both `i==n` and `j==m` may be replaced with true, even in separate expressions. This commit uses a new internal utility function `tvm::arith::ExtractConstraints`, which breaks up a boolean expression into a list of true statements. This may be used to reduce duplication elsewhere, such as `const_int_bound.cc` and `iter_affine_map.cc`.
When inside a conditional of `i!=n`, in addition to the previous replacement of `i!=n` with true, we can also replace `i==n` with false.
vinx13
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vinx13
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Previously, in `ConstIntBoundAnalyzer`, entering a conditional such as `if 2==0` could result in the expression `2` being treated as having a known value of zero within the body of the conditional. Evaluating the range of expressions using `2` in the body of the conditional could result in exceptions being thrown, such as evaluating `expr / 2` while setting `2` to its maximum value of zero. This issue was present for conditions with inequalities for some time, but was introduced for conditions with equalities in apache#11524. Both types are resolved in this PR.
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…1859) Previously, in `ConstIntBoundAnalyzer`, entering a conditional such as `if 2==0` could result in the expression `2` being treated as having a known value of zero within the body of the conditional. Evaluating the range of expressions using `2` in the body of the conditional could result in exceptions being thrown, such as evaluating `expr / 2` while setting `2` to its maximum value of zero. This issue was present for conditions with inequalities for some time, but was introduced for conditions with equalities in #11524. Both types are resolved in this PR.
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…ache#11859) Previously, in `ConstIntBoundAnalyzer`, entering a conditional such as `if 2==0` could result in the expression `2` being treated as having a known value of zero within the body of the conditional. Evaluating the range of expressions using `2` in the body of the conditional could result in exceptions being thrown, such as evaluating `expr / 2` while setting `2` to its maximum value of zero. This issue was present for conditions with inequalities for some time, but was introduced for conditions with equalities in apache#11524. Both types are resolved in this PR.
blackkker
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…ache#11859) Previously, in `ConstIntBoundAnalyzer`, entering a conditional such as `if 2==0` could result in the expression `2` being treated as having a known value of zero within the body of the conditional. Evaluating the range of expressions using `2` in the body of the conditional could result in exceptions being thrown, such as evaluating `expr / 2` while setting `2` to its maximum value of zero. This issue was present for conditions with inequalities for some time, but was introduced for conditions with equalities in apache#11524. Both types are resolved in this PR.
mikeseven
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…ache#11859) Previously, in `ConstIntBoundAnalyzer`, entering a conditional such as `if 2==0` could result in the expression `2` being treated as having a known value of zero within the body of the conditional. Evaluating the range of expressions using `2` in the body of the conditional could result in exceptions being thrown, such as evaluating `expr / 2` while setting `2` to its maximum value of zero. This issue was present for conditions with inequalities for some time, but was introduced for conditions with equalities in apache#11524. Both types are resolved in this PR.
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This adds additional simplifications to
RewriteSimplifierwhile inside a conditional statement. These are simplifications that are expected to be necessary for simplifying conditionals for padding buffer transforms. The main additions are below:RewriteSimplifier::literal_constraints_for simplifications of boolean expressions. Previously, this was only used for simplifications inside atir.likelyannotation.RewriteSimplifier::literal_constraints_to identify known false constraints. This allows a constraint ofi!=nto simplifyi==nto false.EqNodeconstraints inConstIntBoundAnalyzer. Previously, inequalities were used as comparisons. With this change ani==5constraint be used to reduce the bounds ofito[5,5].