[llvm] [LoopRotation] Enable LoopRotation with -Oz if header folds (PR #72842)

[Daniil Fukalov via llvm-commits]

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@@ -365,6 +365,65 @@ static void updateBranchWeights(BranchInst &PreHeaderBI, BranchInst &LoopBI,
   }
 }
 
+// Check if duplicating the header to the preheader will fold all duplicated
+// instructions, terminating with an unconditional jump. So No code duplication
+// would be necessary.
+static bool canRotateWithoutDuplication(Loop *L, llvm::LoopInfo *LI,
+                                        llvm::SimplifyQuery SQ) {
+  BasicBlock *OrigHeader = L->getHeader();
+  BasicBlock *OrigPreheader = L->getLoopPreheader();
+
+  BranchInst *T = dyn_cast<BranchInst>(OrigHeader->getTerminator());
+  assert(T && T->isConditional() && "Header Terminator should be conditional!");
+
+  // a value map to holds the values incoming from preheader
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dfukalov wrote:

Would you please reformat this comment and some of them below, capitalizing first letter and period at the end of sentences.

https://github.com/llvm/llvm-project/pull/72842