…ent (#1139)" (#1141)

This reverts commit 980321d.

We introduce a 2-bit field called CheckedScopeSpecifier in the Stmt class.
During parsing when a compound statement is created we iterate the elements
(statements) of the compound statement and set the checked scope specifier for
each element to the checked scope specifier of the compound statement.

We can get the checked scope specifier for a statement by calling the
getCheckedScopeSpecifier method on the statement.

* Updated the instructions for upgrade of LLVM/Clang.
Also added a new file LLVM-Upgrade-Notes.md to track important
information related to upgrades.

* Fixed typos.

* Addressed review comments.

* Fixed an inadvertent deletion.

* Addressed review comments.

* Incorporated review comments.

* Fixed minor typos.

* Fixed typos.

…BoundsExpr

Add InferredFact and adjust WhereClauseFact to be a subclass of AbstractFact

`IsSwitchCaseBlock`: use `dyn_cast_or_null` to cover the null pointer
case.

`ConditionOnEdge`: do not test if there is no edge between
pred to curr since it will only be called if there is an edge.

`GetModifiedVars`: use `TranspareCasts` to bypass some casting.
The feature to deal with membership access and the array indexing is
still TODO.

from the previous available facts analysis)

It also fixes a bug to visit dead blocks.

…-wip

The community has introduced a new annotation called "contains-errors" on AST
nodes that contain semantic errors. As a result, after the upgrade of Checked C
sources to LLVM 12 we need to check if an expr contains errors before operating
on the expr. One such place is in InverseUtil::IsInvertible where we need to
check if the input modifying expr contains errors.

* Added containsErrors checks to InverUtil::Inverse

Support bounds widening in presence of complex conditionals like:
  "if (*p != 0)", "if ((c = *p) == 'a')", etc.

… 1 in TargetSrcEquality (#1162)

* Add AllowTempEquality parameter to RecordEqualityWithTarget

* Use a ModifiedSameValue variable to determine the return value for UpdateSameValueAfterAssignment

* Rename ModifiedSameValue to RemovedAnyExprs and clean up comments

…nces (#1163)

* In CheckAddressOfOperand, add case for address-of array subscripts to C99-specific logic

* Move address-of array subscript check after other checks such as taking the address of an lvalue

* Adjust expected AST output to account for different types of address-of array subscripts

* Restore deleted comment about checking for array subscript expressions

* Add comment explaining the placement of the address-of array subscript logic

* Put &e1[e2] typing rules under a Checked C flag