[SandboxIR] Implement UnreachableInst

[wizardengineer]

This patch implements the UnreachableInst instruction in SandboxIR. Mirroring llvm::UnreachableInst.

cc: @vporpo

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[vporpo]

Hmm does the test actually pass?

For the instruction to be created as a sanbdoxir::UnreachableInst we need to add the following code in Value *Context::getOrCreateValueInternal(llvm::Value *LLVMV, llvm::User *U):

  case llvm::Instruction::Unreachable: {
    auto *LLVMUnreachable = cast<llvm::UnreachableInst>(LLVMV);
    It->second = std::unique_ptr<UnreachableInst>(new UnreachableInst(LLVMUnreachable, *this));
    return It->second.get();
  }

[wizardengineer]

Hmm does the test actually pass?

For the instruction to be created as a sanbdoxir::UnreachableInst we need to add the following code in Value *Context::getOrCreateValueInternal(llvm::Value *LLVMV, llvm::User *U):

  case llvm::Instruction::Unreachable: {
    auto *LLVMUnreachable = cast<llvm::UnreachableInst>(LLVMV);
    It->second = std::unique_ptr<UnreachableInst>(new UnreachableInst(LLVMUnreachable, *this));
    return It->second.get();
  }

Good catch. Interestingly, the test did pass, but I'm not entirely sure why, if the code you sent me is required. It might be a case of "it works on my computer.", where I'm getting a faulty pass. I made sure to add it.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[wizardengineer]

@vporpo is it okay for you to merge this or is there more changes you need me to make?

[wizardengineer]

@vporpo Apologies for the inconvenience and wait, didn't mean to aruptly commit those recent changes. I'm just now seeing your comment about wanting to see the backtrace.

Backtrace

(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x10)
  * frame #0: 0x0000000100099950 SandboxIRTests`llvm::sandboxir::Instruction::getPrevNode() const + 20
    frame #1: 0x000000010009bf54 SandboxIRTests`llvm::sandboxir::UnreachableInst::create(llvm::sandboxir::Instruction*, llvm::sandboxir::Context&) + 36
    frame #2: 0x0000000100033c40 SandboxIRTests`SandboxIRTest_UnreachableInst_Test::TestBody() + 772
    frame #3: 0x0000000100206114 SandboxIRTests`testing::Test::Run() + 528
    frame #4: 0x0000000100206fa0 SandboxIRTests`testing::TestInfo::Run() + 608
    frame #5: 0x0000000100207be8 SandboxIRTests`testing::TestSuite::Run() + 988
    frame #6: 0x0000000100216098 SandboxIRTests`testing::internal::UnitTestImpl::RunAllTests() + 2220
    frame #7: 0x0000000100215774 SandboxIRTests`testing::UnitTest::Run() + 124
    frame #8: 0x00000001001f8170 SandboxIRTests`main + 148
    frame #9: 0x000000018adea0e0 dyld`start + 2360

[vporpo]

I think I figured out what the problem was. I have updated the comments. To summarize, just drop ret void and change the code to InsertBefore UI, and the test should pass.

[vporpo]

Looks good, thanks for the patch!