[llvm] [SimplifyCFG] Use range check in simplifyBranchOnICmpChain if possible (PR #165105)

[Antonio Frighetto via llvm-commits]

================
@@ -5228,32 +5228,53 @@ bool SimplifyCFGOpt::simplifyBranchOnICmpChain(BranchInst *BI,
         CompVal, DL.getIntPtrType(CompVal->getType()), "magicptr");
   }
 
-  // Create the new switch instruction now.
-  SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size());
-  if (HasProfile) {
-    // We know the weight of the default case. We don't know the weight of the
-    // other cases, but rather than completely lose profiling info, we split
-    // the remaining probability equally over them.
-    SmallVector<uint32_t> NewWeights(Values.size() + 1);
-    NewWeights[0] = BranchWeights[1]; // this is the default, and we swapped if
-                                      // TrueWhenEqual.
-    for (auto &V : drop_begin(NewWeights))
-      V = BranchWeights[0] / Values.size();
-    setBranchWeights(*New, NewWeights, /*IsExpected=*/false);
-  }
-
-  // Add all of the 'cases' to the switch instruction.
-  for (ConstantInt *Val : Values)
-    New->addCase(Val, EdgeBB);
-
-  // We added edges from PI to the EdgeBB.  As such, if there were any
-  // PHI nodes in EdgeBB, they need entries to be added corresponding to
-  // the number of edges added.
-  for (BasicBlock::iterator BBI = EdgeBB->begin(); isa<PHINode>(BBI); ++BBI) {
-    PHINode *PN = cast<PHINode>(BBI);
-    Value *InVal = PN->getIncomingValueForBlock(BB);
-    for (unsigned i = 0, e = Values.size() - 1; i != e; ++i)
-      PN->addIncoming(InVal, BB);
+  // Check if we can represent the values can be represented as a contiguous
----------------
antoniofrighetto wrote:

```suggestion
  // Check if we can represent the values as a contiguous
```

https://github.com/llvm/llvm-project/pull/165105