[IR] Support or disjoint in hasPoisonGeneratingFlags()

This fixed incorrect removal of freeze instructions.

Author: nikic

llvm/lib/IR/Operator.cpp

@@ -32,6 +32,8 @@ bool Operator::hasPoisonGeneratingFlags() const {
   case Instruction::AShr:
   case Instruction::LShr:
     return cast<PossiblyExactOperator>(this)->isExact();
+  case Instruction::Or:
+    return cast<PossiblyDisjointInst>(this)->isDisjoint();
   case Instruction::GetElementPtr: {
     auto *GEP = cast<GEPOperator>(this);
     // Note: inrange exists on constexpr only

llvm/test/Transforms/InstSimplify/freeze-noundef.ll

@@ -29,11 +29,11 @@ define i1 @or(i1 noundef %x, i1 noundef %x2) {
   ret i1 %z
 }
 
-; FIXME: This is a miscompile.
 define i1 @or_disjoint(i1 noundef %x, i1 noundef %x2) {
 ; CHECK-LABEL: @or_disjoint(
 ; CHECK-NEXT:    [[Y:%.*]] = or disjoint i1 [[X:%.*]], [[X2:%.*]]
-; CHECK-NEXT:    ret i1 [[Y]]
+; CHECK-NEXT:    [[Z:%.*]] = freeze i1 [[Y]]
+; CHECK-NEXT:    ret i1 [[Z]]
 ;
   %y = or disjoint i1 %x, %x2
   %z = freeze i1 %y