[llvm] [LAA] Compute pointer bounds for pattern with urem operation (PR #106574)

[David Sherwood via llvm-commits]

================
@@ -809,9 +837,14 @@ class AccessAnalysis {
 /// If \p Assume, try harder to prove that we can compute the bounds of \p Ptr
 /// by adding run-time checks (overflow checks) if necessary.
 static bool hasComputableBounds(PredicatedScalarEvolution &PSE, Value *Ptr,
-                                const SCEV *PtrScev, Loop *L, bool Assume) {
+                                const SCEV *PtrScev, const Loop *L,
+                                bool Assume) {
+  ScalarEvolution *SE = PSE.getSE();
   // The bounds for loop-invariant pointer is trivial.
-  if (PSE.getSE()->isLoopInvariant(PtrScev, L))
+  if (SE->isLoopInvariant(PtrScev, L))
+    return true;
+
+  if (getStartAndEndForURemAccess(*SE, PtrScev, L))
----------------
david-arm wrote:

Maybe it makes sense to add this extra code once we've failed to get the AddRec expression below? Also, it looks like you don't really need to call `getStartAndEndForURemAccess` here, since you don't require an actual SCEV expression at this point. For example, you could split `getStartAndEndForURemAccess` up into two parts - one to see if this is a valid urem access and the other to return the SCEV pair. Something like

```
getStartAndEndForURemAccess() {
  if (!isValidURemAccess())
    return std::nullopt;
...
}

hasComputableBounds() {
...
  if (!AR)
    return isValidURemAccess();
...
}

https://github.com/llvm/llvm-project/pull/106574