[llvm] [MachineSink] Fix missing sinks along critical edges (PR #97618)

[Alexander Kornienko via llvm-commits]

alexfh wrote:

The reduced test case is:
```
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "aarch64-generic-linux-gnu"

define void @_f(ptr %project, i1 %cmp.i.i.not9.i) {
entry:
  %bf.load.i.i.i.i = load i8, ptr %project, align 1
  %tobool.i.i.i.i = icmp slt i8 %bf.load.i.i.i.i, 0
  br i1 %tobool.i.i.i.i, label %cond.true.i9.i.i, label %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE16__get_short_sizeEv.exit.i.i.i

cond.true.i9.i.i:                                 ; preds = %entry
  %0 = load i64, ptr %project, align 8
  br label %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4cendEv.exit

_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE16__get_short_sizeEv.exit.i.i.i: ; preds = %entry
  %conv13.i.i.i.i = zext i8 %bf.load.i.i.i.i to i64
  br label %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4cendEv.exit

_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4cendEv.exit: ; preds = %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE16__get_short_sizeEv.exit.i.i.i, %cond.true.i9.i.i
  %cond.i8.i.i5 = phi i64 [ %0, %cond.true.i9.i.i ], [ %conv13.i.i.i.i, %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE16__get_short_sizeEv.exit.i.i.i ]
  br i1 %cmp.i.i.not9.i, label %common.ret, label %for.body.i

for.cond.i:                                       ; preds = %for.body.i
  %incdec.ptr.i.i = getelementptr i8, ptr %__first.sroa.0.010.i, i64 1
  %cmp.i.i.not.i = icmp eq i64 %cond.i8.i.i5, 0
  br i1 %cmp.i.i.not.i, label %common.ret, label %for.body.i

for.body.i:                                       ; preds = %for.cond.i, %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4cendEv.exit
  %__first.sroa.0.010.i = phi ptr [ %incdec.ptr.i.i, %for.cond.i ], [ %project, %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4cendEv.exit ]
  %1 = load i8, ptr %__first.sroa.0.010.i, align 1
  %isdigit = icmp eq i8 %1, 0
  br i1 %isdigit, label %cond.false, label %for.cond.i

common.ret:                                       ; preds = %cond.end.i.thread.i.i72, %cond.false, %for.cond.i, %_ZNKSt3__u12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4cendEv.exit
  ret void

cond.false:                                       ; preds = %for.body.i
  br i1 %tobool.i.i.i.i, label %common.ret, label %cond.end.i.thread.i.i72

cond.end.i.thread.i.i72:                          ; preds = %cond.false
  %conv13.i.i.i.i73 = zext i8 %bf.load.i.i.i.i to i64
  store i64 %conv13.i.i.i.i73, ptr %project, align 8
  br label %common.ret
}
```

```
./clang-checked-bad -O2 --target=aarch64-generic-linux-gnu -mcpu=neoverse-n1 -mtune=generic -fsanitize=hwaddress -mllvm -hwasan-inline-fast-path-checks=0 -c reduced.ll -o /dev/null
assertion failed at llvm-project/llvm/lib/CodeGen/MachineBasicBlock.cpp:877 in void llvm::MachineBasicBlock::replaceSuccessor(MachineBasicBlock *, MachineBasicBlock *): OldI != E && "Old is not a successor of this block"
    @     0x556998ae3cc4  __assert_fail
    @     0x556997022219  llvm::MachineBasicBlock::replaceSuccessor()
    @     0x5569970239b6  llvm::MachineBasicBlock::SplitCriticalEdge()
    @     0x5569971558fc  (anonymous namespace)::MachineSinking::runOnMachineFunction()
    @     0x55699709c590  llvm::MachineFunctionPass::runOnFunction()
    @     0x556998795cb2  llvm::FPPassManager::runOnFunction()
    @     0x55699879dbc4  llvm::FPPassManager::runOnModule()
    @     0x5569987967a3  llvm::legacy::PassManagerImpl::run()
    @     0x55699355f9fc  clang::EmitBackendOutput()
    @     0x5569931b6a3c  clang::CodeGenAction::ExecuteAction()
    @     0x556993e9d4c3  clang::FrontendAction::Execute()
    @     0x556993e17d8d  clang::CompilerInstance::ExecuteAction()
    @     0x556992e2a6d8  clang::ExecuteCompilerInvocation()
    @     0x556992e1ead6  cc1_main()
...
```

Please fix or revert. Thanks!

https://github.com/llvm/llvm-project/pull/97618