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

[Matt Arsenault via llvm-commits]

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@@ -5187,6 +5187,58 @@ 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(UINT64_C(1) << ShiftValue);
+      if (ConstAlign >= AlignAA->getKnownAlign())
+        return Align(1);
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arsenm wrote:

The return value here should be >= ConstAlign. Instead of hardcoding 1, I don't get why can't you just return ConstAlign

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