[BoundsWidening] Adding all bounds widening analysis commits #1122
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added 8 commits
July 6, 2021 10:28
We separate out BoundsVars into BoundsVarsLower and BoundsVarsUpper that track the variables occurring in the lower and upper bounds expressions, respectively. This is needed for the bounds widenening analysis where we want to determine the variables that can potentially be widened in a given dereference expression.
In preparation for the new bounds widening analysis we rename some variables in the existing implementation because these variables will be defined in the new implementation.
Added a method called PreorderAST::GetExprIntDiff that computes the integer difference between two input expressions and returns true if the expressions are comparable. If the expressions are not comparable then it returns false. This method will be used in the updated bounds widening analysis. This method is meant to replace PreorderAST::GetDerefOffset after the updated bounds widening analysis merges. See #1078
This is an updated implementation of the dataflow analysis for bounds widening. In addition to the existing support for bounds widening on a conditional dereferencing a null-terminated array at its upper bound this implementation also supports bounds widening in presence of _Where clauses. For example: _Nt_array_ptr<char> p : bounds(p, p + 1); int x = strlen(p) _Where p : bounds(p, p + x); In the above example the bounds of p would be widened to bounds(p, p + x) after the call to strlen.
…ds.cpp We invoke the updated BoundsWideningAnalysis::WidenBounds() method from SemaBounds.cpp. We also add new test cases for bounds widening and delete the old test cases.
For each statement update the observed bounds in the BlockState with the widened bounds as computed by the updated bounds widening analysis. The bounds of variables whose bounds are killed are reset to the declared bounds. This PR also updates the method GetBoundsWidenedAndNotKilled that returns the bounds widened in a block before a given statement and not killed by that statement.
The updated implementation of the bounds widening analysis is now in committed. So we can remove the old implementation.
This was referenced Jul 9, 2021
This was referenced Jan 17, 2022
[BoundsWidening] Implement the bounds widening dataflow analysis
checkedc/checkedc-llvm-project#1093
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This PR contains all commits required for the updated bounds widening analysis.