[clang] [llvm] [RISCV] Implement the implications of C extension (PR #132259)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `premerge-monolithic-linux` running on `premerge-linux-1` while building `clang,llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/26585

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'lld :: ELF/riscv-attributes.s' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 3: rm -rf /build/buildbot/premerge-monolithic-linux/build/tools/lld/test/ELF/Output/riscv-attributes.s.tmp && split-file /build/buildbot/premerge-monolithic-linux/llvm-project/lld/test/ELF/riscv-attributes.s /build/buildbot/premerge-monolithic-linux/build/tools/lld/test/ELF/Output/riscv-attributes.s.tmp && cd /build/buildbot/premerge-monolithic-linux/build/tools/lld/test/ELF/Output/riscv-attributes.s.tmp
+ rm -rf /build/buildbot/premerge-monolithic-linux/build/tools/lld/test/ELF/Output/riscv-attributes.s.tmp
+ split-file /build/buildbot/premerge-monolithic-linux/llvm-project/lld/test/ELF/riscv-attributes.s /build/buildbot/premerge-monolithic-linux/build/tools/lld/test/ELF/Output/riscv-attributes.s.tmp
+ cd /build/buildbot/premerge-monolithic-linux/build/tools/lld/test/ELF/Output/riscv-attributes.s.tmp
RUN: at line 4: /build/buildbot/premerge-monolithic-linux/build/bin/llvm-mc -filetype=obj -triple=riscv64 a.s -o a.o
+ /build/buildbot/premerge-monolithic-linux/build/bin/llvm-mc -filetype=obj -triple=riscv64 a.s -o a.o
RUN: at line 5: /build/buildbot/premerge-monolithic-linux/build/bin/ld.lld -e 0 a.o -o out 2>&1 | /build/buildbot/premerge-monolithic-linux/build/bin/count 0
+ /build/buildbot/premerge-monolithic-linux/build/bin/ld.lld -e 0 a.o -o out
+ /build/buildbot/premerge-monolithic-linux/build/bin/count 0
RUN: at line 6: /build/buildbot/premerge-monolithic-linux/build/bin/llvm-readelf -S -l --arch-specific out | /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck /build/buildbot/premerge-monolithic-linux/llvm-project/lld/test/ELF/riscv-attributes.s --check-prefixes=HDR,CHECK
+ /build/buildbot/premerge-monolithic-linux/build/bin/llvm-readelf -S -l --arch-specific out
+ /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck /build/buildbot/premerge-monolithic-linux/llvm-project/lld/test/ELF/riscv-attributes.s --check-prefixes=HDR,CHECK
/build/buildbot/premerge-monolithic-linux/llvm-project/lld/test/ELF/riscv-attributes.s:107:8: error: HDR: expected string not found in input
# HDR: .riscv.attributes RISCV_ATTRIBUTES 0000000000000000 000158 00005a 00 0 0 1{{$}}
       ^
<stdin>:4:50: note: scanning from here
 [Nr] Name Type Address Off Size ES Flg Lk Inf Al
                                                 ^
<stdin>:7:7: note: possible intended match here
 [ 2] .riscv.attributes RISCV_ATTRIBUTES 0000000000000000 000158 000068 00 0 0 1
      ^

Input file: <stdin>
Check file: /build/buildbot/premerge-monolithic-linux/llvm-project/lld/test/ELF/riscv-attributes.s

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

Input was:
<<<<<<
             1: There are 7 section headers, starting at offset 0x238: 
             2:  
             3: Section Headers: 
             4:  [Nr] Name Type Address Off Size ES Flg Lk Inf Al 
check:107'0                                                      X error: no match found
             5:  [ 0] NULL 0000000000000000 000000 000000 00 0 0 0 
check:107'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             6:  [ 1] .text PROGBITS 0000000000011158 000158 000000 00 AX 0 0 4 
check:107'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             7:  [ 2] .riscv.attributes RISCV_ATTRIBUTES 0000000000000000 000158 000068 00 0 0 1 
check:107'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
check:107'1           ?                                                                           possible intended match
             8:  [ 3] .comment PROGBITS 0000000000000000 0001c0 000008 01 MS 0 0 1 
check:107'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             9:  [ 4] .symtab SYMTAB 0000000000000000 0001c8 000030 18 6 2 8 
check:107'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...

```

</details>

https://github.com/llvm/llvm-project/pull/132259