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

[Matt Arsenault via llvm-commits]

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@@ -5188,6 +5188,81 @@ 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()) {
+      if (ConstVals->isAtFixpoint()) {
+        const DataLayout &DL = A.getDataLayout();
+        unsigned Size =
+            DL.getPointerTypeSizeInBits(II->getOperand(0)->getType());
+        uint64_t TrailingZeros = Size - 1;
+        for (const APInt &It : ConstVals->getAssumedSet())
+          if (It.countTrailingZeros() < TrailingZeros)
+            TrailingZeros = It.countTrailingZeros();
+
+        APInt Mask = APInt(Size, 1).shl(TrailingZeros);
+        APInt PtrAlign = APInt(Size, 1).shl(Log2(AlignAA->getKnownAlign()));
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arsenm wrote:

APInt::getSignMask (but can you also just use APInt::isAligned?)

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