[clang] [CLANG][AArch64] Add the modal 8 bit floating-point scalar type (PR #97277)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-armv8-quick` running on `linaro-clang-armv8-quick` while building `clang` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/6441

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: AST/arm-mfp8.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/lib/clang/20/include -nostdsysteminc -std=c++11 -triple aarch64-arm-none-eabi -target-feature -fp8 -ast-dump /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/AST/arm-mfp8.cpp |   /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/AST/arm-mfp8.cpp --strict-whitespace
+ /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/AST/arm-mfp8.cpp --strict-whitespace
+ /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/lib/clang/20/include -nostdsysteminc -std=c++11 -triple aarch64-arm-none-eabi -target-feature -fp8 -ast-dump /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/AST/arm-mfp8.cpp
/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/AST/arm-mfp8.cpp:72:16: error: CHECK-NEXT: expected string not found in input
//CHECK-NEXT:  | |       `-DeclRefExpr {{.*}} '__mfp8':'__MFloat8_t' lvalue ParmVar {{.*}}8 'arg' '__mfp8':'__MFloat8_t'
               ^
<stdin>:70872:86: note: scanning from here
| |     `-ImplicitCastExpr 0xa2af968 <col:13> '__mfp8':'__MFloat8_t' <LValueToRValue>
                                                                                     ^
<stdin>:70873:22: note: possible intended match here
| |       `-DeclRefExpr 0xa2af950 <col:13> '__mfp8':'__MFloat8_t' lvalue ParmVar 0xa2af660 'arg' '__mfp8':'__MFloat8_t'
                     ^

Input file: <stdin>
Check file: /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/AST/arm-mfp8.cpp

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           .
           .
           .
       70867: | | `-CompoundStmt 0xa2af940 <col:39, col:41> 
       70868: | |-CXXMethodDecl 0xa2af718 <line:45:3, line:47:3> line:45:10 func1c '__mfp8 (__mfp8)' implicit-inline 
       70869: | | |-ParmVarDecl 0xa2af660 <col:17, col:24> col:24 used arg '__mfp8':'__MFloat8_t' 
       70870: | | `-CompoundStmt 0xa2af984 <col:30, line:47:3> 
       70871: | |   `-ReturnStmt 0xa2af978 <line:46:5, col:13> 
       70872: | |     `-ImplicitCastExpr 0xa2af968 <col:13> '__mfp8':'__MFloat8_t' <LValueToRValue> 
next:72'0                                                                                          X error: no match found
       70873: | |       `-DeclRefExpr 0xa2af950 <col:13> '__mfp8':'__MFloat8_t' lvalue ParmVar 0xa2af660 'arg' '__mfp8':'__MFloat8_t' 
next:72'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
next:72'1                          ?                                                                                                   possible intended match
       70874: | `-CXXMethodDecl 0xa2af800 <line:48:3, line:50:3> line:48:17 func2c '__mfp8 (__mfp8)' static implicit-inline 
next:72'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       70875: |   |-ParmVarDecl 0xa2af7a0 <col:24, col:31> col:31 used arg '__mfp8':'__MFloat8_t' 
next:72'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       70876: |   `-CompoundStmt 0xa2af9cc <col:36, line:50:3> 
next:72'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       70877: |     `-ReturnStmt 0xa2af9c0 <line:49:5, col:12> 
next:72'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       70878: |       `-ImplicitCastExpr 0xa2af9b0 <col:12> '__mfp8':'__MFloat8_t' <LValueToRValue> 
next:72'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           .
           .
...

```

</details>

https://github.com/llvm/llvm-project/pull/97277