Setting approximateSource to true for fir.pack_array.

Author: vzakhari

flang/lib/Optimizer/Analysis/AliasAnalysis.cpp

@@ -548,6 +548,7 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v,
           // the array operand.
           v = op.getArray();
           defOp = v.getDefiningOp();
+          approximateSource = true;
         })
         .Case<fir::BoxAddrOp>([&](auto op) {
           v = op->getOperand(0);

flang/test/Analysis/AliasAnalysis/alias-analysis-pack-array.fir

@@ -3,19 +3,41 @@
 // fir.pack_array is a pass-through operation for FIR alias analysis.
 // RUN: fir-opt %s --test-fir-alias-analysis -split-input-file --mlir-disable-threading 2>&1 | FileCheck %s
 
-// CHECK: test1_y(1)#0 <-> test1_x(1)#0: NoAlias
+// The two pointers referencing two different maybe repacked
+// versions of the original dummy arguments do not alias:
+// CHECK-DAG: test1_y_repack(1)#0 <-> test1_x_repack(1)#0: NoAlias
+// CHECK-DAG: test1_x_orig(1)#0 <-> test1_y_orig(1)#0: NoAlias
+
+// Repacked dummy does not alias with another original dummy:
+// CHECK-DAG: test1_y_repack(1)#0 <-> test1_x_orig(1)#0: NoAlias
+// CHECK-DAG: test1_x_repack(1)#0 <-> test1_y_orig(1)#0: NoAlias
+
+// Repacked dummy may alias with its original:
+// CHECK-DAG: test1_x_repack(1)#0 <-> test1_x_orig(1)#0: MayAlias
+// CHECK-DAG: test1_y_repack(1)#0 <-> test1_y_orig(1)#0: MayAlias
+
+// Ideally, these should report MustAlias, but MayAlias
+// may work as well:
+// CHECK-DAG: test1_y_repack(1)#0 <-> test1_y_repack2(1)#0: MayAlias
+// CHECK-DAG: test1_x_repack(1)#0 <-> test1_x_repack2(1)#0: MayAlias
+
+
 func.func @_QFtest1(%arg0: !fir.box<!fir.array<?xf32>> {fir.bindc_name = "x"}, %arg1: !fir.box<!fir.array<?xf32>> {fir.bindc_name = "y"}) {
   %c1 = arith.constant 1 : index
   %0 = fir.dummy_scope : !fir.dscope
   %1 = fir.pack_array %arg0 heap whole : (!fir.box<!fir.array<?xf32>>) -> !fir.box<!fir.array<?xf32>>
   %2:2 = hlfir.declare %1 dummy_scope %0 {uniq_name = "_QFtest1Ex"} : (!fir.box<!fir.array<?xf32>>, !fir.dscope) -> (!fir.box<!fir.array<?xf32>>, !fir.box<!fir.array<?xf32>>)
   %3 = fir.pack_array %arg1 heap whole : (!fir.box<!fir.array<?xf32>>) -> !fir.box<!fir.array<?xf32>>
   %4:2 = hlfir.declare %3 dummy_scope %0 {uniq_name = "_QFtest1Ey"} : (!fir.box<!fir.array<?xf32>>, !fir.dscope) -> (!fir.box<!fir.array<?xf32>>, !fir.box<!fir.array<?xf32>>)
-  %5 = hlfir.designate %4#0 (%c1) {test.ptr = "test1_y(1)"} : (!fir.box<!fir.array<?xf32>>, index) -> !fir.ref<f32>
+  %5 = fir.box_addr %4#0 {test.ptr = "test1_y_repack(1)"} : (!fir.box<!fir.array<?xf32>>) -> !fir.ref<f32>
+  %52 = fir.box_addr %4#0 {test.ptr = "test1_y_repack2(1)"} : (!fir.box<!fir.array<?xf32>>) -> !fir.ref<f32>
   %6 = fir.load %5 : !fir.ref<f32>
-  %7 = hlfir.designate %2#0 (%c1) {test.ptr = "test1_x(1)"} : (!fir.box<!fir.array<?xf32>>, index) -> !fir.ref<f32>
+  %7 = fir.box_addr %2#0 {test.ptr = "test1_x_repack(1)"} : (!fir.box<!fir.array<?xf32>>) -> !fir.ref<f32>
+  %72 = fir.box_addr %2#0 {test.ptr = "test1_x_repack2(1)"} : (!fir.box<!fir.array<?xf32>>) -> !fir.ref<f32>
   hlfir.assign %6 to %7 : f32, !fir.ref<f32>
   fir.unpack_array %3 to %arg1 heap : !fir.box<!fir.array<?xf32>>
   fir.unpack_array %1 to %arg0 heap : !fir.box<!fir.array<?xf32>>
+  %8 = fir.box_addr %arg0 {test.ptr = "test1_x_orig(1)"} : (!fir.box<!fir.array<?xf32>>) -> !fir.ref<f32>
+  %9 = fir.box_addr %arg1 {test.ptr = "test1_y_orig(1)"} : (!fir.box<!fir.array<?xf32>>) -> !fir.ref<f32>
   return
 }