[clang] [llvm] [RISCV] Update P extension to the 018 version of the spec. (PR #170399)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-gcc-ubuntu` running on `sie-linux-worker3` while building `clang,llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/174/builds/28545

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/RISCV/rvp-ext-rv32.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/llc -mtriple=riscv32 -mattr=+experimental-p -enable-p-ext-codegen -verify-machineinstrs < /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/CodeGen/RISCV/rvp-ext-rv32.ll | /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/FileCheck --check-prefixes=CHECK,CHECK-RV32 /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/CodeGen/RISCV/rvp-ext-rv32.ll
# executed command: /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/llc -mtriple=riscv32 -mattr=+experimental-p -enable-p-ext-codegen -verify-machineinstrs
# note: command had no output on stdout or stderr
# executed command: /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/FileCheck --check-prefixes=CHECK,CHECK-RV32 /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/CodeGen/RISCV/rvp-ext-rv32.ll
# .---command stderr------------
# | /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/CodeGen/RISCV/rvp-ext-rv32.ll:719:20: error: CHECK-RV32-NEXT: expected string not found in input
# | ; CHECK-RV32-NEXT: ppack.dh a2, a4, a6
# |                    ^
# | <stdin>:629:16: note: scanning from here
# |  sll a5, a1, a2
# |                ^
# | <stdin>:630:2: note: possible intended match here
# |  ppaire.db a2, a4, a6
# |  ^
# | 
# | Input file: <stdin>
# | Check file: /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/CodeGen/RISCV/rvp-ext-rv32.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |              1:  .attribute 4, 16 
# |              2:  .attribute 5, "rv32i2p1_p0p18" 
# |              3:  .file "<stdin>" 
# |              4:  .text 
# |              5:  .globl test_padd_h # -- Begin function test_padd_h 
# |              6:  .p2align 2 
# |              7:  .type test_padd_h, at function 
# |              8: test_padd_h: # @test_padd_h 
# | label:7'0       ^~~~~~~~~~~~
# | label:7'1       ^~~~~~~~~~~~
# |              9:  .cfi_startproc 
# |             10: # %bb.0: 
# | check:8         ^~~~~~~~
# |             11:  lw a1, 0(a1) 
# | next:9           ^~~~~~~~~~~~
# |             12:  lw a2, 0(a2) 
# | next:10          ^~~~~~~~~~~~
# |             13:  padd.h a1, a1, a2 
# | next:11          ^~~~~~~~~~~~~~~~~
# |             14:  sw a1, 0(a0) 
# | next:12          ^~~~~~~~~~~~
# |             15:  ret 
...

```

</details>

https://github.com/llvm/llvm-project/pull/170399