[clang] [InstCombine] Add combines/simplifications for `llvm.ptrmask` (PR #67166)

[via cfe-commits]

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@@ -898,6 +910,53 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
         }
         break;
       }
+      case Intrinsic::ptrmask: {
+        // Fail loudly in case this is ever changed.
+        // Likely not much needs to be changed here to support vector types.
+        assert(!I->getOperand(0)->getType()->isVectorTy() &&
+               !I->getOperand(1)->getType()->isVectorTy() &&
+               "These simplifications where written at a time when ptrmask did "
+               "not support vector types and may not work for vectors");
+
+        unsigned MaskWidth = I->getOperand(1)->getType()->getScalarSizeInBits();
+        RHSKnown = KnownBits(MaskWidth);
+        // If either the LHS or the RHS are Zero, the result is zero.
+        if (SimplifyDemandedBits(I, 0, DemandedMask, LHSKnown, Depth + 1) ||
+            SimplifyDemandedBits(
+                I, 1, (DemandedMask & ~LHSKnown.Zero).zextOrTrunc(MaskWidth),
+                RHSKnown, Depth + 1))
+          return I;
+
+        RHSKnown = RHSKnown.zextOrTrunc(BitWidth);
+        assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?");
+        assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?");
+
+        Known = LHSKnown & RHSKnown;
+        KnownBitsComputed = DemandedMask.isAllOnes();
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goldsteinn wrote:

At the moment sure, but could imagine otherwise?

https://github.com/llvm/llvm-project/pull/67166