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Gabor Marton 20f8733d4b [Analyzer][solver] Simplification: Do a fixpoint iteration before the eq class merge 
This reverts commit f02c5f3478 and
addresses the issue mentioned in D114619 differently.

Repeating the issue here:
Currently, during symbol simplification we remove the original member
symbol from the equivalence class (`ClassMembers` trait). However, we
keep the reverse link (`ClassMap` trait), in order to be able the query
the related constraints even for the old member. This asymmetry can lead
to a problem when we merge equivalence classes:
```
ClassA: [a, b]   // ClassMembers trait,
a->a, b->a       // ClassMap trait, a is the representative symbol
```
Now let,s delete `a`:
```
ClassA: [b]
a->a, b->a
```
Let's merge ClassA into the trivial class `c`:
```
ClassA: [c, b]
c->c, b->c, a->a
```
Now, after the merge operation, `c` and `a` are actually in different
equivalence classes, which is inconsistent.

This issue manifests in a test case (added in D103317):
```
void recurring_symbol(int b) {
  if (b * b != b)
    if ((b * b) * b * b != (b * b) * b)
      if (b * b == 1)
}
```
Before the simplification we have these equivalence classes:
```
trivial EQ1: [b * b != b]
trivial EQ2: [(b * b) * b * b != (b * b) * b]
```

During the simplification with `b * b == 1`, EQ1 is merged with `1 != b`
`EQ1: [b * b != b, 1 != b]` and we remove the complex symbol, so
`EQ1: [1 != b]`
Then we start to simplify the only symbol in EQ2:
`(b * b) * b * b != (b * b) * b --> 1 * b * b != 1 * b --> b * b != b`
But `b * b != b` is such a symbol that had been removed previously from
EQ1, thus we reach the above mentioned inconsistency.

This patch addresses the issue by making it impossible to synthesise a
symbol that had been simplified before. We achieve this by simplifying
the given symbol to the absolute simplest form.

Differential Revision: https://reviews.llvm.org/D114887
 		2021-12-01 22:23:41 +01:00
..
INPUTS
…
bindings Recommit: Compress formatting of array type names (int [4] -> int[4]) 2021-10-21 11:34:43 -07:00
cmake [Fuchsia][CMake] Don't set libcxxabi and libunwind variables on Windows 2021-11-11 19:29:39 -08:00
docs Add toggling for -fnew-infallible/-fno-new-infallible 2021-11-30 17:19:53 -08:00
examples [clang][driver] Add -fplugin-arg- to pass arguments to plugins 2021-11-25 10:47:55 +01:00
include [NFC][Clang] Fix some comments in clang 2021-12-01 13:36:46 -05:00
lib [Analyzer][solver] Simplification: Do a fixpoint iteration before the eq class merge 2021-12-01 22:23:41 +01:00
runtime
…
test [Analyzer][solver] Simplification: Do a fixpoint iteration before the eq class merge 2021-12-01 22:23:41 +01:00
tools [clang-offload-bundler] Reuse original file extension for device archive member 2021-11-30 20:38:59 -08:00
unittests Fix a violated precondition in clang-format. 2021-12-01 14:39:00 +01:00
utils [NFC][clang]Inclusive language: remove remaining uses of sanity 2021-11-24 14:20:13 -05:00
www [NFC] Inclusive language: Remove instances of master in URLs 2021-11-05 08:48:41 -05:00
.clang-format
…
.clang-tidy
…
.gitignore
…
CMakeLists.txt [clang] Remove CLANG_ROUND_TRIP_CC1_ARGS and always roundtrip in +assert builds 2021-11-18 08:31:21 -05:00
CODE_OWNERS.TXT
…
INSTALL.txt
…
LICENSE.TXT
…
ModuleInfo.txt
…
NOTES.txt
…
README.txt
…

README.txt 

//===----------------------------------------------------------------------===//
// C Language Family Front-end
//===----------------------------------------------------------------------===//

Welcome to Clang.  This is a compiler front-end for the C family of languages
(C, C++, Objective-C, and Objective-C++) which is built as part of the LLVM
compiler infrastructure project.

Unlike many other compiler frontends, Clang is useful for a number of things
beyond just compiling code: we intend for Clang to be host to a number of
different source-level tools.  One example of this is the Clang Static Analyzer.

If you're interested in more (including how to build Clang) it is best to read
the relevant web sites.  Here are some pointers:

Information on Clang:             http://clang.llvm.org/
Building and using Clang:         http://clang.llvm.org/get_started.html
Clang Static Analyzer:            http://clang-analyzer.llvm.org/
Information on the LLVM project:  http://llvm.org/

If you have questions or comments about Clang, a great place to discuss them is
on the Clang development mailing list:
  http://lists.llvm.org/mailman/listinfo/cfe-dev

If you find a bug in Clang, please file it in the LLVM bug tracker:
  http://llvm.org/bugs/