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

[Alexander Richardson via cfe-commits]

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@@ -6411,6 +6411,40 @@ static Value *simplifyBinaryIntrinsic(Function *F, Value *Op0, Value *Op1,
       return Constant::getNullValue(ReturnType);
     break;
   }
+  case Intrinsic::ptrmask: {
+    if (isa<PoisonValue>(Op0) || isa<PoisonValue>(Op1))
+      return PoisonValue::get(Op0->getType());
+
+    // NOTE: We can't apply this simplifications based on the value of Op1
+    // because we need to preserve provenance.
+    if (Q.isUndefValue(Op0) || match(Op0, m_Zero()))
+      return Constant::getNullValue(Op0->getType());
+
+    if (Op1->getType()->getScalarSizeInBits() ==
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arichardson wrote:

It is redundant since it does not affect more than the index bits (see clarification in the langref added in https://github.com/llvm/llvm-project/pull/69343)

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