[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 `lld-x86_64-ubuntu-fast` running on `as-builder-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/33/builds/10596

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

Command Output (stderr):
--
RUN: at line 2: not /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+real-true16 -show-encoding /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s | /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/FileCheck --check-prefixes=GFX11,W32 /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
+ /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/FileCheck --check-prefixes=GFX11,W32 /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
+ not /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+real-true16 -show-encoding /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
llvm-mc: /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/include/llvm/ADT/SmallVector.h:295: const T& llvm::SmallVectorTemplateCommon<T, <template-parameter-1-2> >::operator[](llvm::SmallVectorTemplateCommon<T, <template-parameter-1-2> >::size_type) const [with T = llvm::MCOperand; <template-parameter-1-2> = void; llvm::SmallVectorTemplateCommon<T, <template-parameter-1-2> >::const_reference = const llvm::MCOperand&; llvm::SmallVectorTemplateCommon<T, <template-parameter-1-2> >::size_type = long unsigned int]: 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: /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+real-true16 -show-encoding /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s
 #0 0x0000560edcc3a300 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc+0xdcd300)
 #1 0x0000560edcc378ef llvm::sys::RunSignalHandlers() (/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc+0xdca8ef)
 #2 0x0000560edcc37a34 SignalHandler(int) Signals.cpp:0:0
 #3 0x00007f3ee6aa6520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007f3ee6afa9fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007f3ee6aa6476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007f3ee6a8c7f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007f3ee6a8c71b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007f3ee6a9de96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000560edc47b435 (anonymous namespace)::AMDGPUAsmParser::validateInstruction(llvm::MCInst const&, llvm::SMLoc const&, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand>>> const&) AMDGPUAsmParser.cpp:0:0
#10 0x0000560edc47d272 (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) AMDGPUAsmParser.cpp:0:0
#11 0x0000560edcb96c21 (anonymous namespace)::AsmParser::parseAndMatchAndEmitTargetInstruction((anonymous namespace)::ParseStatementInfo&, llvm::StringRef, llvm::AsmToken, llvm::SMLoc) AsmParser.cpp:0:0
#12 0x0000560edcbb2c32 (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&, llvm::MCAsmParserSemaCallback*) (.part.0) AsmParser.cpp:0:0
#13 0x0000560edcba5db9 (anonymous namespace)::AsmParser::Run(bool, bool) AsmParser.cpp:0:0
#14 0x0000560edc3c0b05 main (/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc+0x553b05)
#15 0x00007f3ee6a8dd90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#16 0x00007f3ee6a8de40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#17 0x0000560edc3d40a5 _start (/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc+0x5670a5)
error: Aborted (core dumped)
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/FileCheck --check-prefixes=GFX11,W32 /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/MC/AMDGPU/gfx11_asm_vop3_from_vopc.s

--

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


```

</details>

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