[llvm] [SCEV] Infer loop max trip count from memory accesses (PR #70361)

[Florian Mayer via llvm-commits]

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@@ -8191,6 +8204,132 @@ ScalarEvolution::getSmallConstantTripMultiple(const Loop *L,
   return getSmallConstantTripMultiple(L, ExitCount);
 }
 
+/// Collect all load/store instructions that must be executed in every iteration
+/// of loop \p L .
+static void
+collectExecLoadStoreInsideLoop(const Loop *L, DominatorTree &DT,
+                               SmallVector<Instruction *, 4> &MemInsts) {
+  // It is difficult to tell if the load/store instruction is executed on every
+  // iteration inside an irregular loop.
+  if (!L->isLoopSimplifyForm() || !L->isInnermost())
+    return;
+
+  // FIXME: To make the case more typical, we only analyze loops that have one
+  // exiting block and the block must be the latch. It is easier to capture
+  // loops with memory access that will be executed in every iteration.
+  const BasicBlock *LoopLatch = L->getLoopLatch();
+  assert(LoopLatch && "normal form loop doesn't have a latch");
+  if (L->getExitingBlock() != LoopLatch)
+    return;
+
+  const Function *F = LoopLatch->getParent();
+  if (F->hasFnAttribute(Attribute::SanitizeAddress) ||
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fmayer wrote:

Could you add a comment why we are doing this?

https://github.com/llvm/llvm-project/pull/70361