[llvm] [Attributor] Propagate alignment through ptrmask (PR #150158)

[Matt Arsenault via llvm-commits]

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@@ -5187,6 +5187,59 @@ struct AADereferenceableCallSiteReturned final
 // ------------------------ Align Argument Attribute ------------------------
 
 namespace {
+
+Align getKnownAlignForIntrinsic(Attributor &A, AAAlign &QueryingAA,
+                                const IntrinsicInst &II) {
+  switch (II.getIntrinsicID()) {
+  case Intrinsic::ptrmask: {
+    const auto *ConstVals = A.getAAFor<AAPotentialConstantValues>(
+        QueryingAA, IRPosition::value(*(II.getOperand(1))), DepClassTy::NONE);
+    const auto *AlignAA = A.getAAFor<AAAlign>(QueryingAA, IRPosition::value(II),
+                                              DepClassTy::NONE);
+    if (ConstVals && ConstVals->isValidState() && ConstVals->isAtFixpoint()) {
+      unsigned ShiftValue =
+          std::min(ConstVals->getAssumedMinTrailingZeros(), (unsigned)63);
+      Align ConstAlign(1 << ShiftValue);
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arsenm wrote:

The 1 is an int, so this will still be UB. Feels like Align is missing a good constructor for this case.Use `PowerOf2Ceil(ConstVals->getAssumedMinTrailingZeros() - 1)`?

https://github.com/llvm/llvm-project/pull/150158