Fix regression on min reduction

This makes sure that the generated IR doesn't change as a result of this
PR. The generated IR looks wrong to me (no reduction is generated at
all), but that is a matter for another patch.

Author: tblah

flang/lib/Lower/OpenMP/ReductionProcessor.cpp

@@ -371,6 +371,19 @@ void ReductionProcessor::addReductionDecl(
       std::get<Fortran::parser::OmpReductionOperator>(reduction.t)};
   const auto &objectList{std::get<Fortran::parser::OmpObjectList>(reduction.t)};
 
+  if (!std::holds_alternative<Fortran::parser::DefinedOperator>(
+          redOperator.u)) {
+    if (const auto *reductionIntrinsic =
+            std::get_if<Fortran::parser::ProcedureDesignator>(&redOperator.u)) {
+      if (!ReductionProcessor::supportedIntrinsicProcReduction(
+              *reductionIntrinsic)) {
+        return;
+      }
+    } else {
+      return;
+    }
+  }
+
   // initial pass to collect all recuction vars so we can figure out if this
   // should happen byref
   for (const Fortran::parser::OmpObject &ompObject : objectList.v) {

flang/test/Lower/OpenMP/wsloop-reduction-min2.f90

@@ -0,0 +1,41 @@
+! RUN: bbc -emit-hlfir -fopenmp -o - %s | FileCheck %s
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -o - %s | FileCheck %s
+
+! regression test for crash
+
+program reduce
+integer :: i = 0
+integer :: r = 0
+
+!$omp parallel do reduction(min:r)
+do i=0,10
+   r = i
+enddo
+!$omp end parallel do
+
+print *,r
+
+end program
+
+! TODO: the reduction is not curently lowered correctly. This test is checking
+! that we do not crash and we still produce the same broken IR as before.
+
+! CHECK-LABEL:   func.func @_QQmain() attributes {fir.bindc_name = "reduce"} {
+! CHECK:           %[[VAL_0:.*]] = fir.address_of(@_QFEi) : !fir.ref<i32>
+! CHECK:           %[[VAL_1:.*]]:2 = hlfir.declare %[[VAL_0]] {uniq_name = "_QFEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:           %[[VAL_2:.*]] = fir.address_of(@_QFEr) : !fir.ref<i32>
+! CHECK:           %[[VAL_3:.*]]:2 = hlfir.declare %[[VAL_2]] {uniq_name = "_QFEr"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:           omp.parallel {
+! CHECK:             %[[VAL_4:.*]] = fir.alloca i32 {adapt.valuebyref, pinned}
+! CHECK:             %[[VAL_5:.*]]:2 = hlfir.declare %[[VAL_4]] {uniq_name = "_QFEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:             %[[VAL_6:.*]] = arith.constant 0 : i32
+! CHECK:             %[[VAL_7:.*]] = arith.constant 10 : i32
+! CHECK:             %[[VAL_8:.*]] = arith.constant 1 : i32
+! CHECK:             omp.wsloop  for  (%[[VAL_9:.*]]) : i32 = (%[[VAL_6]]) to (%[[VAL_7]]) inclusive step (%[[VAL_8]]) {
+! CHECK:               fir.store %[[VAL_9]] to %[[VAL_5]]#1 : !fir.ref<i32>
+! CHECK:               %[[VAL_10:.*]] = fir.load %[[VAL_5]]#0 : !fir.ref<i32>
+! CHECK:               hlfir.assign %[[VAL_10]] to %[[VAL_3]]#0 : i32, !fir.ref<i32>
+! CHECK:               omp.yield
+! CHECK:             }
+! CHECK:             omp.terminator
+! CHECK:           }