[clang] [RISCV][P-Ext] Remove builtins for pmerge with signed types. (PR #225975)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-aarch64-ubuntu` running on `linaro-lldb-aarch64-ubuntu` while building `clang` at step 6 "test".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/37863

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

```
Step 6 (test) failure: build (failure)
...
PASS: lldb-unit :: Host/./HostTests/5/11 (2673 of 2683)
PASS: lldb-unit :: Target/./TargetTests/2/13 (2674 of 2683)
PASS: lldb-unit :: Target/./TargetTests/3/13 (2675 of 2683)
PASS: lldb-unit :: Host/./HostTests/6/11 (2676 of 2683)
PASS: lldb-unit :: Host/./HostTests/7/11 (2677 of 2683)
PASS: lldb-unit :: Host/./HostTests/2/11 (2678 of 2683)
PASS: lldb-unit :: Host/./HostTests/3/11 (2679 of 2683)
PASS: lldb-unit :: Process/gdb-remote/./ProcessGdbRemoteTests/8/13 (2680 of 2683)
PASS: lldb-unit :: Process/gdb-remote/./ProcessGdbRemoteTests/9/13 (2681 of 2683)
UNRESOLVED: lldb-api :: tools/lldb-dap/output/TestDAP_output.py (2682 of 2683)
******************** TEST 'lldb-api :: tools/lldb-dap/output/TestDAP_output.py' FAILED ********************
Script:
--
/usr/bin/python3.10 /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./lib --env LLVM_INCLUDE_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/include --env LLVM_TOOLS_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin --triple aarch64-unknown-linux-gnu --build-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build --lldb-module-cache-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build/module-cache-lldb/lldb-api --clang-module-cache-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build/module-cache-clang/lldb-api --executable /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/lldb --lldb-python-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/local/lib/python3.10/dist-packages --compiler /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/clang --dsymutil /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/dsymutil --make /usr/bin/gmake --llvm-tools-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin --lldb-obj-root /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/tools/lldb --lldb-libs-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./lib --cmake-build-type Release /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/tools/lldb-dap/output -p TestDAP_output.py --timeout 600
--
Exit Code: 1

Command Output (stdout):
--
Skipping the following test categories: libc++, msvcstl, dsym, pdb, gmodules, debugserver, objc

--
Command Output (stderr):
--
FAIL: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_output (TestDAP_output.TestDAP_output)
Log Files:
 - /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build/tools/lldb-dap/output/TestDAP_output/Error_test_output.log
======================================================================
ERROR: test_output (TestDAP_output.TestDAP_output)
   Test output handling for the running process.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/tools/lldb-dap/output/TestDAP_output.py", line 43, in test_output
    session.disconnect()
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/session_helpers.py", line 1718, in disconnect
    response = self.send_request(args).result()
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/session.py", line 99, in result
    response = self.result_or_error()
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/tools/lldb_dap/session.py", line 116, in result_or_error
    raw = self._future.result(timeout=self._timeout)
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 460, in result
    raise TimeoutError()
concurrent.futures._base.TimeoutError: 
	Request 'disconnect' (seq=7) timed out after 50.0s
Config=aarch64-/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang
----------------------------------------------------------------------
Ran 1 test in 100.325s

FAILED (errors=1)

```

</details>

https://github.com/llvm/llvm-project/pull/225975