[flang] Skip OPTIONAL arguments in LoopVersioning.

This patch fixes multiple tests failing with segfault due to accessing
absent argument box before the loop versioning check.
The absent arguments might be treated as contiguous for the purpose
of loop versioning, but this is not done in this patch.

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D158800

Author: vzakhari

flang/lib/Optimizer/Transforms/LoopVersioning.cpp

@@ -141,6 +141,14 @@ void LoopVersioningPass::runOnOperation() {
   fir::KindMapping kindMap = fir::getKindMapping(module);
   mlir::SmallVector<ArgInfo, 4> argsOfInterest;
   for (auto &arg : args) {
+    // Optional arguments must be checked for IsPresent before
+    // looking for the bounds. They are unsupported for the time being.
+    if (func.getArgAttrOfType<mlir::UnitAttr>(arg.getArgNumber(),
+                                              fir::getOptionalAttrName())) {
+      LLVM_DEBUG(llvm::dbgs() << "OPTIONAL is not supported\n");
+      continue;
+    }
+
     if (auto seqTy = getAsSequenceType(&arg)) {
       unsigned rank = seqTy.getDimension();
       if (rank > 0 &&

flang/test/Transforms/loop-versioning.fir

@@ -522,4 +522,52 @@ func.func @sum1dfixed(%arg0: !fir.ref<!fir.array<?xf64>> {fir.bindc_name = "a"},
 // CHECK: fir.store %[[IF_RES]]#1 to %{{.*}}
 // CHECK: return
 
+// Check that OPTIONAL argument's box is not accessed illegally
+// before the loop.
+func.func @test_optional_arg(%arg0: !fir.box<!fir.array<?xf32>> {fir.bindc_name = "x", fir.optional}) {
+  %c1 = arith.constant 1 : index
+  %c20 = arith.constant 20 : index
+  %c0_i64 = arith.constant 0 : i64
+  %0 = fir.alloca i32 {bindc_name = "i", uniq_name = "_QMcheck_modFtestEi"}
+  %1 = fir.convert %c1 : (index) -> i32
+  %2:2 = fir.do_loop %arg1 = %c1 to %c20 step %c1 iter_args(%arg2 = %1) -> (index, i32) {
+    fir.store %arg2 to %0 : !fir.ref<i32>
+    %3 = fir.is_present %arg0 : (!fir.box<!fir.array<?xf32>>) -> i1
+    fir.if %3 {
+      %8 = fir.coordinate_of %arg0, %c0_i64 : (!fir.box<!fir.array<?xf32>>, i64) -> !fir.ref<f32>
+    } else {
+    }
+    %4 = arith.addi %arg1, %c1 : index
+    %5 = fir.convert %c1 : (index) -> i32
+    %6 = fir.load %0 : !fir.ref<i32>
+    %7 = arith.addi %6, %5 : i32
+    fir.result %4, %7 : index, i32
+  }
+  fir.store %2#1 to %0 : !fir.ref<i32>
+  return
+}
+// CHECK-LABEL:   func.func @test_optional_arg(
+// CHECK-SAME:                                 %[[VAL_0:.*]]: !fir.box<!fir.array<?xf32>> {fir.bindc_name = "x", fir.optional}) {
+// CHECK-NEXT:           %[[VAL_1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:           %[[VAL_2:.*]] = arith.constant 20 : index
+// CHECK-NEXT:           %[[VAL_3:.*]] = arith.constant 0 : i64
+// CHECK-NEXT:           %[[VAL_4:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QMcheck_modFtestEi"}
+// CHECK-NEXT:           %[[VAL_5:.*]] = fir.convert %[[VAL_1]] : (index) -> i32
+// CHECK-NEXT:           %[[VAL_6:.*]]:2 = fir.do_loop %[[VAL_7:.*]] = %[[VAL_1]] to %[[VAL_2]] step %[[VAL_1]] iter_args(%[[VAL_8:.*]] = %[[VAL_5]]) -> (index, i32) {
+// CHECK-NEXT:             fir.store %[[VAL_8]] to %[[VAL_4]] : !fir.ref<i32>
+// CHECK-NEXT:             %[[VAL_9:.*]] = fir.is_present %[[VAL_0]] : (!fir.box<!fir.array<?xf32>>) -> i1
+// CHECK-NEXT:             fir.if %[[VAL_9]] {
+// CHECK-NEXT:               %[[VAL_10:.*]] = fir.coordinate_of %[[VAL_0]], %[[VAL_3]] : (!fir.box<!fir.array<?xf32>>, i64) -> !fir.ref<f32>
+// CHECK-NEXT:             } else {
+// CHECK-NEXT:             }
+// CHECK-NEXT:             %[[VAL_11:.*]] = arith.addi %[[VAL_7]], %[[VAL_1]] : index
+// CHECK-NEXT:             %[[VAL_12:.*]] = fir.convert %[[VAL_1]] : (index) -> i32
+// CHECK-NEXT:             %[[VAL_13:.*]] = fir.load %[[VAL_4]] : !fir.ref<i32>
+// CHECK-NEXT:             %[[VAL_14:.*]] = arith.addi %[[VAL_13]], %[[VAL_12]] : i32
+// CHECK-NEXT:             fir.result %[[VAL_11]], %[[VAL_14]] : index, i32
+// CHECK-NEXT:           }
+// CHECK-NEXT:           fir.store %[[VAL_15:.*]]#1 to %[[VAL_4]] : !fir.ref<i32>
+// CHECK-NEXT:           return
+// CHECK-NEXT:         }
+
 } // End module