[llvm] [LoopPeel] Ignore assume intrinsics for the mayWriteToMemory check in peelToTurnInvariantLoadsDereferenceable. (PR #171547)

[Nikita Popov via llvm-commits]

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@@ -447,7 +447,10 @@ static unsigned peelToTurnInvariantLoadsDereferenceable(Loop &L,
   const DataLayout &DL = L.getHeader()->getDataLayout();
   for (BasicBlock *BB : L.blocks()) {
     for (Instruction &I : *BB) {
-      if (I.mayWriteToMemory())
+      // Don't consider llvm.assume as writing to memory.
+      if (I.mayWriteToMemory() &&
+          !(isa<IntrinsicInst>(I) &&
+            cast<IntrinsicInst>(I).getIntrinsicID() == Intrinsic::assume))
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nikic wrote:

Ah, if the motivation is to hoist invariant loads, the writing check makes sense. In that case it should be fine to generalize the assume case to inaccessiblemem, because that can never alias with loads.

https://github.com/llvm/llvm-project/pull/171547