[flang][docs] Replace references to f18 in the docs with flang (Part 1)

Some light editing of some of the text was also done. The remaining
references will be replaced in a later commit.

Author: tarunprabhu

flang/docs/AssumedRank.md

@@ -101,9 +101,9 @@ Assumed-rank dummies are also represented in the
 represent assumed-rank in procedure characteristics.
 
 ### Runtime Representation of Assumed-Ranks
-Assumed-ranks are implemented as CFI_cdesc_t (18.5.3) with the addition of an
-f18 specific addendum when required for the type. This is the usual f18
-descriptor, and no changes is required to represent assumed-ranks in this data
+Assumed-ranks are implemented as CFI_cdesc_t (18.5.3) with the addition of a
+Flang specific addendum when required for the type. This is the usual Flang
+descriptor, and no changes are required to represent assumed-ranks in this data
 structure. In fact, there is no difference between the runtime descriptor
 created for an assumed shape and the runtime descriptor created when the
 corresponding entity is passed as an assumed-rank.
@@ -143,11 +143,11 @@ SSA values for assumed-rank entities have an MLIR type containing a
 (additionally wrapped in a `!fir.ref` type for pointers and allocatables).
 
 Examples:
-`INTEGER :: x(..)`  -> `!fir.box<!fir.array<* x i32>>` 
+`INTEGER :: x(..)`  -> `!fir.box<!fir.array<* x i32>>`
 `CLASS(*) :: x(..)`  -> `!fir.class<!fir.array<* x none>>`
 `TYPE(*) :: x(..)`  -> `!fir.box<!fir.array<* x none>>`
 `REAL, ALLOCATABLE :: x(..)`  -> `!fir.ref<!fir.box<!fir.heap<!fir.array<* x f32>>>>`
-`TYPE(t), POINTER :: x(..)`  -> `!fir.ref<!fir.box<!fir.ptr<!fir.array<* x !fir.type<t>>>>>` 
+`TYPE(t), POINTER :: x(..)`  -> `!fir.ref<!fir.box<!fir.ptr<!fir.array<* x !fir.type<t>>>>>`
 
 All these FIR types are implemented as the address of a CFI_cdesc_t in code
 generation.
@@ -187,7 +187,7 @@ could still be relevant:
   support assumed-ranks, but `fir.box_tdesc` would require change since the
   position of the type descriptor pointer depends on the rank.
 - as `fir.allocmem` / `fir.global` result (assumed-ranks are never local/global
-  entities). 
+  entities).
 - as `fir.embox` result (When creating descriptor for an explicit shape, the
   descriptor can be created with the entity rank, and then casted via
 `fir.convert`).
@@ -449,7 +449,7 @@ subroutine test(x)
       real :: x(..)
     end subroutine
   end interface
-  
+
   real :: x(..)
   select rank (y => x)
   rank(*)
@@ -531,7 +531,7 @@ print *, len(x)
 
 ```
 %ele_size = fir.box_elesize %x : (!fir.box<!fir.array<*x!fir.char<?>>>) -> i64
-# .... divide by character KIND byte size if needed as usual 
+# .... divide by character KIND byte size if needed as usual
 ```
 #### PRESENT
 Implemented inline with `fir.is_present` which ends-up implemented as a check
@@ -564,7 +564,7 @@ present and is constant, `fir.box_dim` can also be used with the option to add
 a runtime check that RANK <= DIM. Pointers and allocatables are dereferenced,
 which in FIR currently creates a descriptor copy that cannot be simplified
 like for the previous inquiries by inserting a cast before the fir.load (the
-dimension info must be correctly copied). 
+dimension info must be correctly copied).
 
 #### LBOUND, SHAPE, and UBOUND
 When DIM is present an is present, the runtime can be used as it is currently

flang/docs/C++17.md

@@ -1,12 +1,12 @@
-<!--===- docs/C++17.md 
-  
+<!--===- docs/C++17.md
+
    Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
    See https://llvm.org/LICENSE.txt for license information.
    SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-  
+
 -->
 
-# C++14/17 features used in f18
+# C++14/17 features used in Flang
 
 ```{contents}
 ---
@@ -27,7 +27,7 @@ out the details of how our C++ code should look and gives
 guidance about feature usage.
 
 We have chosen to use some features of the recent C++17
-language standard in f18.
+language standard in Flang.
 The most important of these are:
 * sum types (discriminated unions) in the form of `std::variant`
 * `using` template parameter packs
@@ -41,7 +41,7 @@ in this list because it's not particularly well known.)
 ## Sum types
 
 First, some background information to explain the need for sum types
-in f18.
+in Flang.
 
 Fortran is notoriously problematic to lex and parse, as tokenization
 depends on the state of the partial parse;
@@ -57,7 +57,7 @@ a unified lexer/parser.
 We have chosen to do so because it is simpler and should reduce
 both initial bugs and long-term maintenance.
 
-Specifically, f18's parser uses the technique of recursive descent with
+Specifically, Flang's parser uses the technique of recursive descent with
 backtracking.
 It is constructed as the incremental composition of pure parsing functions
 that each, when given a context (location in the input stream plus some state),
@@ -73,7 +73,7 @@ of Fortran.
 
 The specification of Fortran uses a form of BNF with alternatives,
 optional elements, sequences, and lists.  Each of these constructs
-in the Fortran grammar maps directly in the f18 parser to both
+in the Fortran grammar maps directly in Flang's parser to both
 the means of combining other parsers as alternatives, &c., and to
 the declarations of the parse tree data structures that represent
 the results of successful parses.
@@ -87,10 +87,10 @@ The bounded polymorphism supplied by the C++17 `std::variant` fits
 those needs exactly.
 For example, production R502 in Fortran defines the top-level
 program unit of Fortran as being a function, subroutine, module, &c.
-The `struct ProgramUnit` in the f18 parse tree header file
+`struct ProgramUnit` in the Flang parse tree header file
 represents each program unit with a member that is a `std::variant`
 over the six possibilities.
-Similarly, the parser for that type in the f18 grammar has six alternatives,
+Similarly, the parser for that type in Flang's grammar has six alternatives,
 each of which constructs an instance of `ProgramUnit` upon the result of
 parsing a `Module`, `FunctionSubprogram`, and so on.
 
@@ -99,7 +99,7 @@ parse is typically implemented with overloaded functions.
 A function instantiated on `ProgramUnit` will use `std::visit` to
 identify the right alternative and perform the right actions.
 The call to `std::visit` must pass a visitor that can handle all
-of the possibilities, and f18 will fail to build if one is missing.
+of the possibilities, and Flang will fail to build if one is missing.
 
 Were we unable to use `std::variant` directly, we would likely
 have chosen to implement a local `SumType` replacement; in the

flang/docs/C++style.md

@@ -1,9 +1,9 @@
-<!--===- docs/C++style.md 
-  
+<!--===- docs/C++style.md
+
    Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
    See https://llvm.org/LICENSE.txt for license information.
    SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-  
+
 -->
 
 # Flang C++ Style Guide
@@ -30,7 +30,7 @@ is clear on usage, follow it.
   is pretty good and comes with lots of justifications for its rules.
 * Reasonable exceptions to these guidelines can be made.
 * Be aware of some workarounds for known issues in older C++ compilers that should
-  still be able to compile f18. They are listed at the end of this document.
+  still be able to compile Flang. They are listed at the end of this document.
 
 ## In particular:
 
@@ -261,7 +261,7 @@ move semantics, member access, and comparison for equality; suitable for use in
 `std::variant<>`.
 * `std::unique_ptr<>`: A nullable pointer with ownership, null by default,
 not copyable, reassignable.
-F18 has a helpful `Deleter<>` class template that makes `unique_ptr<>`
+Flang has a helpful `Deleter<>` class template that makes `unique_ptr<>`
 easier to use with forward-referenced data types.
 * `std::shared_ptr<>`: A nullable pointer with shared ownership via reference
 counting, null by default, shallowly copyable, reassignable, and slow.
@@ -312,9 +312,9 @@ Consistency is one of many aspects in the pursuit of clarity,
 but not an end in itself.
 
 ## C++ compiler bug workarounds
-Below is a list of workarounds for C++ compiler bugs met with f18 that, even
-if the bugs are fixed in latest C++ compiler versions, need to be applied so
-that all desired tool-chains can compile f18.
+Below is a list of workarounds for C++ compiler bugs encountered when building
+Flang. Even if the bugs are fixed in latest C++ compiler versions, these need to
+be applied so that all desired tool-chains can compile Flang.
 
 ### Explicitly move noncopyable local variable into optional results
 
@@ -338,7 +338,7 @@ std::optional<CantBeCopied> fooOK() {
 }
 ```
 The underlying bug is actually not specific to `std::optional` but this is the most common
-case in f18 where the issue may occur. The actual bug can be reproduced with any class `B`
+case in Flang where the issue may occur. The actual bug can be reproduced with any class `B`
 that has a perfect forwarding constructor taking `CantBeCopied` as argument:
 `template<typename CantBeCopied> B(CantBeCopied&& x) x_{std::forward<CantBeCopied>(x)} {}`.
 In such scenarios, Ubuntu 18.04 g++ fails to instantiate the move constructor

flang/docs/Calls.md

@@ -529,7 +529,7 @@ PGI passes host instance links in descriptors in additional arguments
 that are not always successfully forwarded across implicit interfaces,
 sometimes leading to crashes when they turn out to be needed.
 
-F18 will manage a pool of trampolines in its runtime support library
+Flang will manage a pool of trampolines in its runtime support library
 that can be used to pass internal procedures as effective arguments
 to F77ish procedures, so that
 a bare code address can serve to represent the effective argument.
@@ -569,14 +569,14 @@ Fortran 2018 explicitly enables us to do this with a correction to Fortran
 2003 in 4.3.4(5).
 
 Last, there must be reasonably permanent naming conventions used
-by the F18 runtime library for those unrestricted specific intrinsic
+by Flang's runtime library for those unrestricted specific intrinsic
 functions (table 16.2 in 16.8) and extensions that can be passed as
 arguments.
 
 In these cases where external naming is at the discretion
 of the implementation, we should use names that are not in the C language
 user namespace, begin with something that identifies
-the current incompatible version of F18, the module, the submodule, and
+the current incompatible version of Flang, the module, the submodule, and
 elemental SIMD width, and are followed by the external name.
 The parts of the external name can be separated by some character that
 is acceptable for use in LLVM IR and assembly language but not in user

flang/docs/Character.md

@@ -6,7 +6,7 @@
 
 -->
 
-# Implementation of `CHARACTER` types in f18
+# Implementation of `CHARACTER` types in Flang
 
 ```{contents}
 ---
@@ -16,7 +16,7 @@ local:
 
 ## Kinds and Character Sets
 
-The f18 compiler and runtime support three kinds of the intrinsic
+The Flang compiler and runtime support three kinds of the intrinsic
 `CHARACTER` type of Fortran 2018.
 The default (`CHARACTER(KIND=1)`) holds 8-bit character codes;
 `CHARACTER(KIND=2)` holds 16-bit character codes;
@@ -108,12 +108,12 @@ The result of `//` may be used
 * as the value of a specifier of an I/O statement,
 * or as the value of a statement function.
 
-The f18 compiler has a general (but slow) means of implementing concatenation
+The Flang compiler has a general (but slow) means of implementing concatenation
 and a specialized (fast) option to optimize the most common case.
 
 ### General concatenation
 
-In the most general case, the f18 compiler's generated code and
+In the most general case, Flang's generated code and
 runtime support library represent the result as a deferred-length allocatable
 `CHARACTER` temporary scalar or array variable that is initialized
 as a zero-length array by `AllocatableInitCharacter()`

flang/docs/DoConcurrent.md

@@ -1,9 +1,9 @@
-<!--===- docs/DoConcurrent.md 
-  
+<!--===- docs/DoConcurrent.md
+
    Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
    See https://llvm.org/LICENSE.txt for license information.
    SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-  
+
 -->
 
 # `DO CONCURRENT` isn't necessarily concurrent
@@ -280,7 +280,8 @@ Specifically, an easy means is required that stipulates that localization
 should apply at most only to the obvious cases of local non-pointer
 non-allocatable scalars.
 
-In the LLVM Fortran compiler project (a/k/a "flang", "f18") we considered
+In the LLVM Fortran compiler project (now known as "flang", previously also
+known as "f18") we considered
 several solutions to this problem.
 1. Add syntax (e.g., `DO PARALLEL` or `DO CONCURRENT() DEFAULT(PARALLEL)`)
    by which one can inform the compiler that it should localize only