add nopoison back

Author: el-ev

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

@@ -1132,17 +1132,14 @@ void State::addInfoFor(BasicBlock &BB) {
     case Intrinsic::umax:
     case Intrinsic::smin:
     case Intrinsic::smax:
+    case Intrinsic::usub_sat:
       // TODO: handle llvm.abs as well
       WorkList.push_back(
           FactOrCheck::getCheck(DT.getNode(&BB), cast<CallInst>(&I)));
       // TODO: Check if it is possible to instead only added the min/max facts
       // when simplifying uses of the min/max intrinsics.
-      if (isGuaranteedNotToBePoison(&I))
-        WorkList.push_back(FactOrCheck::getInstFact(DT.getNode(&BB), &I));
-      break;
-    case Intrinsic::usub_sat:
-      WorkList.push_back(
-          FactOrCheck::getCheck(DT.getNode(&BB), cast<CallInst>(&I)));
+      if (!isGuaranteedNotToBePoison(&I))
+        break;
       [[fallthrough]];
     case Intrinsic::abs:
     case Intrinsic::uadd_sat:

llvm/test/Transforms/ConstraintElimination/uadd-usub-sat.ll

@@ -22,7 +22,8 @@ define i1 @usub_sat_ule_lhs(i64 %a, i64 %b) {
 ; CHECK-LABEL: define i1 @usub_sat_ule_lhs(
 ; CHECK-SAME: i64 [[A:%.*]], i64 [[B:%.*]]) {
 ; CHECK-NEXT:    [[SUB_SAT:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[A]], i64 [[B]])
-; CHECK-NEXT:    ret i1 true
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i64 [[SUB_SAT]], [[A]]
+; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %sub.sat = call i64 @llvm.usub.sat.i64(i64 %a, i64 %b)
   %cmp = icmp ule i64 %sub.sat, %a