[llvm] [LoopSink] check conflicting preheader memory access before sink (PR #195510)

[Nikita Popov via llvm-commits]

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@@ -179,6 +179,25 @@ findBBsToSinkInto(const Loop &L, const SmallPtrSetImpl<BasicBlock *> &UseBBs,
   return BBsToSinkInto;
 }
 
+/// Returns true when an \p I from the \p PreheaderBB has conflicting memory
+/// access over the later preheader instructions.
+static bool hasConflictingPreheaderMemoryAccess(Instruction &I, AAResults *AA,
+                                                BasicBlock *PreheaderBB) {
+  if (!I.mayReadOrWriteMemory())
+    return false;
+
+  for (Instruction &OtherI : make_range(I.getIterator(), PreheaderBB->end())) {
+    if (!OtherI.mayReadOrWriteMemory())
+      continue;
+    if (!I.mayWriteToMemory() && !OtherI.mayWriteToMemory())
+      continue;
+    if (!AA || isModOrRefSet(AA->getModRefInfo(&I, &OtherI)))
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nikic wrote:

Arguments are the wrong way around.

https://github.com/llvm/llvm-project/pull/195510