[llvm] [SimplifyCFG] Use hash map to continue hoisting the common instructions (PR #78615)

[Yingwei Zheng via llvm-commits]

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@@ -1608,16 +1618,39 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(BasicBlock *BB,
 
   auto *TI = BB->getTerminator();
 
+  SmallVector<BasicBlock *, 8> SuccessorBBs;
+  for (auto *Succ : successors(BB)) {
+    BasicBlock::iterator SuccItr = Succ->begin();
+    // If we find an unreachable instruction at the beginning of a basic block,
+    // we can still hoist instructions from the rest of the basic blocks.
+    if (isa<UnreachableInst>(*SuccItr))
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dtcxzyw wrote:

```suggestion
    if (isa<UnreachableInst>(Succ->getFirstNonPHIOrDbg()))
```

https://github.com/llvm/llvm-project/pull/78615