[flang] Add examples in documentation/BijectiveInternalNameUniquing.md

[sameeranjoshi]

Summary

I thought it would be simpler to understand on how the unique names would look like when an example is present. So I added some examples.

I found 2 such places to add examples
-Common blocks
-Module scope global data

[jeanPerier]

Thanks for adding these examples

flang/documentation/BijectiveInternalNameUniquing.md

82

The indentation of module mod is slightly weird. Also, I think you could add end module or ... at the end.

[sameeranjoshi]

Minor formating changes.

[schweitz]

Thanks for adding these examples.

A related addition would be to add a unittest that constructs and deconstructs the unique names.

[sameeranjoshi]

In D79442#2022726, @schweitz wrote:

Thanks for adding these examples.

A related addition would be to add a unittest that constructs and deconstructs the unique names.

Is there some testing guide for the same?
If not, some previous work to look into and check how is that done?

[sameeranjoshi]

In D79442#2022726, @schweitz wrote:

Thanks for adding these examples.

A related addition would be to add a unittest that constructs and deconstructs the unique names.

I checked LLVM unittesting guidelines for writing tests using gtest and gmock.

I grepped for gtest.h and gmock.h, I ended up with no results.
Various macros(various types of ASSERTS... ) in gtest are not seen in flang/unittests/ folder.
As well various gtest related functions in main() are not seen, ex RUN_ALL_TESTS(), InitGoogleTest().

1. I am wondering why are other tests in the directory not using these features of gtest and still being under unittests/ folder?
2. If current tests which are already present belong to different aspect of testing the flang-compiler, is that ok to write BijectiveInternalNameUniquing tests using gtest way of doing things?

[sameeranjoshi]

closed by https://reviews.llvm.org/rGcc4768f2ec7ca1e6421c18afeface61376e9fab7

flang/documentation/BijectiveInternalNameUniquing.md

 ```
     _QMmodSs1modSs2modFsubPfun
 ```
 
 ### Common blocks
 
    * A common block name will be prefixed with `B`
 
+Given:
+```
+   common /variables/ i, j
+```
+
+The uniqued name of `variables` becomes:
+```
+    _QBvariables
+```
+
+Given:
+```
+   common i, j
+```
+
+The uniqued name in case of `blank common block` becomes:
+```
+    _QB
+```
+
 ### Module scope global data
 
    * A global data entity is prefixed with `E`
    * A global entity that is constant (parameter) will be prefixed with `EC`
 
+Given:
+```
+    module mod
+      integer :: intvar
+      real, parameter :: pi = 3.14
+    end module
+```
+
+The uniqued name of `intvar` becomes:
+```
+    _QMmodEintvar
+```
+
+The uniqued name of `pi` becomes:
+```
+    _QMmodECpi
+```
+
 ### Procedures/Subprograms
 
    * A procedure/subprogram is prefixed with `P`
 
 Given:
 ```
     subroutine sub
 ```