[llvm] [AMDGPU][True16][MC] validate op_sel and .l/.h syntax (PR #123250)

[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 `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/21494

<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 'LLVM :: MC/AMDGPU/gfx11_asm_vop3_from_vopc.s' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
RUN: at line 2: not /build/buildbot/premerge-monolithic-linux/build/bin/llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+real-true16 -show-encoding /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s | /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck --check-prefixes=GFX11,W32 /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
+ not /build/buildbot/premerge-monolithic-linux/build/bin/llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+real-true16 -show-encoding /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
+ /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck --check-prefixes=GFX11,W32 /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
llvm-mc: /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/include/llvm/ADT/SmallVector.h:295: const_reference llvm::SmallVectorTemplateCommon<llvm::MCOperand>::operator[](size_type) const [T = llvm::MCOperand]: Assertion `idx < size()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /build/buildbot/premerge-monolithic-linux/build/bin/llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+real-true16 -show-encoding /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
 #0 0x000055e97b21cd88 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/Support/Unix/Signals.inc:798:13
 #1 0x000055e97b21aa8e llvm::sys::RunSignalHandlers() /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/Support/Signals.cpp:106:18
 #2 0x000055e97b21d558 SignalHandler(int) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/Support/Unix/Signals.inc:415:1
 #3 0x0000783e287b8520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x0000783e2880c9fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x0000783e287b8476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x0000783e2879e7f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000783e2879e71b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x0000783e287afe96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x000055e97aca3977 validateInstruction /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp:0:0
#10 0x000055e97aca3977 (anonymous namespace)::AMDGPUAsmParser::matchAndEmitInstruction(llvm::SMLoc, unsigned int&, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand>>>&, llvm::MCStreamer&, unsigned long&, bool) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp:5405:10
#11 0x000055e97b1a8653 (anonymous namespace)::AsmParser::parseAndMatchAndEmitTargetInstruction((anonymous namespace)::ParseStatementInfo&, llvm::StringRef, llvm::AsmToken, llvm::SMLoc) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/MC/MCParser/AsmParser.cpp:2384:27
#12 0x000055e97b19b974 (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&, llvm::MCAsmParserSemaCallback*) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/MC/MCParser/AsmParser.cpp:2317:10
#13 0x000055e97b194ef1 (anonymous namespace)::AsmParser::Run(bool, bool) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/lib/MC/MCParser/AsmParser.cpp:0:0
#14 0x000055e97ac56fae AssembleInput(char const*, llvm::Target const*, llvm::SourceMgr&, llvm::MCContext&, llvm::MCStreamer&, llvm::MCAsmInfo&, llvm::MCSubtargetInfo&, llvm::MCInstrInfo&, llvm::MCTargetOptions const&) /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/tools/llvm-mc/llvm-mc.cpp:348:13
#15 0x000055e97ac560f6 main /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/tools/llvm-mc/llvm-mc.cpp:0:11
#16 0x0000783e2879fd90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#17 0x0000783e2879fe40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#18 0x000055e97ac50e95 _start (/build/buildbot/premerge-monolithic-linux/build/bin/llvm-mc+0x2481e95)
error: Aborted
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck --check-prefixes=GFX11,W32 /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/123250