[flang][TBAA] refine TARGET/POINTER encoding (#170908)

Depends upon #170900

Re-land #169544

Previously we were less specific for POINTER/TARGET: encoding that they
could alias with (almost) anything.

In the new system, the "target data" tree is now a sibling of the other
trees (e.g. "global data"). POITNTER variables go at the root of the
"target data" tree, whereas TARGET variables get their own nodes under
that tree. For example,

```
integer, pointer :: ip
real, pointer :: rp
integer, target :: it
integer, target :: it2(:)
real, target :: rt
integer :: i
real :: r
```
- `ip` and `rp` may alias with any variable except `i` and `r`.
- `it`, `it2`, and `rt` may alias only with `ip` or `rp`.
- `i` and `r` cannot alias with any other variable.

Fortran 2023 15.5.2.14 gives restrictions on entities associated with
dummy arguments. These do not allow non-target globals to be modified
through dummy arguments and therefore I don't think we need to make all
globals alias with dummy arguments.

I haven't implemented it in this patch, but I wonder whether it is ever
possible for `ip` to alias with `rt`.

While I was updating the tests I fixed up some tests that still assumed
that local alloc tbaa wasn't the default.

Cray pointers/pointees are (optionally) modelled as aliasing with all
non-descriptor data. This is not enabled by default.

I found no functional regressions in the gfortran test suite.

Author: tblah

flang/include/flang/Optimizer/Analysis/TBAAForest.h

@@ -99,11 +99,25 @@ struct TBAATree {
   //   |- "any data access"
   //      |
   //      |- "dummy arg data"
-  //      |- "target data"
-  //         |
-  //         |- "allocated data"
-  //         |- "direct data"
-  //         |- "global data"
+  //        |
+  //        |- <dummy arg name 1>
+  //        |- <dummy arg name 2>
+  //      |- "target data" <-- Any POINTER variable or TARGET dummy arg
+  //        |
+  //        |- <target name 1> <--- any TARGET variable which isn't a dummy arg
+  //        |- <target name 2>
+  //      |- "allocated data"
+  //        |
+  //        |- <allocated name 1>
+  //        |- <allocated name 2>
+  //      |- "direct data"
+  //        |
+  //        |- <direct name 1>
+  //        |- <direct name 2>
+  //      |- "global data"
+  //        |
+  //        |- <global name 1>
+  //        |- <global name 2>
   static TBAATree buildTree(mlir::StringAttr functionName);
 
 private:

flang/lib/Optimizer/Analysis/TBAAForest.cpp

@@ -66,12 +66,9 @@ fir::TBAATree::TBAATree(mlir::LLVM::TBAATypeDescriptorAttr anyAccess,
                         mlir::LLVM::TBAATypeDescriptorAttr dataRoot,
                         mlir::LLVM::TBAATypeDescriptorAttr boxMemberTypeDesc)
     : targetDataTree(dataRoot.getContext(), "target data", dataRoot),
-      globalDataTree(dataRoot.getContext(), "global data",
-                     targetDataTree.getRoot()),
-      allocatedDataTree(dataRoot.getContext(), "allocated data",
-                        targetDataTree.getRoot()),
+      globalDataTree(dataRoot.getContext(), "global data", dataRoot),
+      allocatedDataTree(dataRoot.getContext(), "allocated data", dataRoot),
       dummyArgDataTree(dataRoot.getContext(), "dummy arg data", dataRoot),
-      directDataTree(dataRoot.getContext(), "direct data",
-                     targetDataTree.getRoot()),
+      directDataTree(dataRoot.getContext(), "direct data", dataRoot),
       anyAccessDesc(anyAccess), boxMemberTypeDesc(boxMemberTypeDesc),
       anyDataTypeDesc(dataRoot) {}

flang/lib/Optimizer/Transforms/AddAliasTags.cpp

@@ -60,6 +60,9 @@ static llvm::cl::opt<unsigned> localAllocsThreshold(
     llvm::cl::desc("If present, stops generating TBAA tags for accesses of "
                    "local allocations after N accesses in a module"));
 
+// Defined in AliasAnalysis.cpp
+extern llvm::cl::opt<bool> supportCrayPointers;
+
 namespace {
 
 // Return the size and alignment (in bytes) for the given type.
@@ -668,6 +671,7 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
   LLVM_DEBUG(llvm::dbgs() << "Analysing " << op << "\n");
 
   const fir::AliasAnalysis::Source &source = state.getSource(memref);
+  LLVM_DEBUG(llvm::dbgs() << "Got source " << source << "\n");
 
   // Process the scopes, if not processed yet.
   state.processFunctionScopes(func);
@@ -686,14 +690,22 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
   }
 
   mlir::LLVM::TBAATagAttr tag;
-  // TBAA for dummy arguments
-  if (enableDummyArgs &&
-      source.kind == fir::AliasAnalysis::SourceKind::Argument) {
+  // Cray pointer/pointee is a special case. These might alias with any data.
+  if (supportCrayPointers && source.isCrayPointerOrPointee()) {
+    LLVM_DEBUG(llvm::dbgs().indent(2)
+               << "Found reference to Cray pointer/pointee at " << *op << "\n");
+    mlir::LLVM::TBAATypeDescriptorAttr anyDataDesc =
+        state.getFuncTreeWithScope(func, scopeOp).anyDataTypeDesc;
+    tag = mlir::LLVM::TBAATagAttr::get(anyDataDesc, anyDataDesc, /*offset=*/0);
+    // TBAA for dummy arguments
+  } else if (enableDummyArgs &&
+             source.kind == fir::AliasAnalysis::SourceKind::Argument) {
     LLVM_DEBUG(llvm::dbgs().indent(2)
                << "Found reference to dummy argument at " << *op << "\n");
     std::string name = getFuncArgName(llvm::cast<mlir::Value>(source.origin.u));
-    // If it is a TARGET or POINTER, then we do not care about the name,
-    // because the tag points to the root of the subtree currently.
+    // POINTERS can alias with any POINTER or TARGET. Assume that TARGET dummy
+    // arguments might alias with each other (because of the "TARGET" hole for
+    // dummy arguments). See flang/docs/Aliasing.md.
     if (source.isTargetOrPointer()) {
       tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
     } else if (!name.empty()) {
@@ -715,13 +727,10 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
     LLVM_DEBUG(llvm::dbgs().indent(2)
                << "Found reference to global " << globalName.str() << " at "
                << *op << "\n");
-    if (source.isPointer()) {
-      tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
-    } else {
-      // In general, place the tags under the "global data" root.
-      fir::TBAATree::SubtreeState *subTree =
-          &state.getMutableFuncTreeWithScope(func, scopeOp).globalDataTree;
 
+    // Add a named tag inside the given subtree, disambiguating members of a
+    // common block
+    auto addTagUsingStorageDesc = [&](fir::TBAATree::SubtreeState *subTree) {
       mlir::Operation *instantiationPoint = source.origin.instantiationPoint;
       auto storageIface =
           mlir::dyn_cast_or_null<fir::FortranVariableStorageOpInterface>(
@@ -766,6 +775,19 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
         LLVM_DEBUG(llvm::dbgs()
                    << "Tagged under '" << globalName << "' root\n");
       }
+    };
+
+    if (source.isPointer()) {
+      // Pointers can alias with any pointer or target.
+      tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
+    } else if (source.isTarget()) {
+      // Targets could alias with any pointer but not with each other.
+      addTagUsingStorageDesc(
+          &state.getMutableFuncTreeWithScope(func, scopeOp).targetDataTree);
+    } else {
+      // In general, place the tags under the "global data" root.
+      addTagUsingStorageDesc(
+          &state.getMutableFuncTreeWithScope(func, scopeOp).globalDataTree);
     }
 
     // TBAA for global variables with descriptors
@@ -776,9 +798,17 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
       const char *name = glbl.getRootReference().data();
       LLVM_DEBUG(llvm::dbgs().indent(2) << "Found reference to direct " << name
                                         << " at " << *op << "\n");
+      // Pointer can alias with any pointer or target so that gets the root.
       if (source.isPointer())
         tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
+      // Targets could alias with any pointer but not with each other so they
+      // get their own node inside of the target data tree.
+      else if (source.isTarget())
+        tag = state.getFuncTreeWithScope(func, scopeOp)
+                  .targetDataTree.getTag(name);
       else
+        // Boxes that are not pointers or targets cannot alias with those that
+        // are. Put them under global data.
         tag = state.getFuncTreeWithScope(func, scopeOp)
                   .directDataTree.getTag(name);
     } else {
@@ -815,8 +845,13 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
                  << "\n");
     } else if (source.isPointer() && state.attachLocalAllocTag()) {
       LLVM_DEBUG(llvm::dbgs().indent(2)
-                 << "Found reference to allocation at " << *op << "\n");
+                 << "Found reference to POINTER allocation at " << *op << "\n");
       tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
+    } else if (source.isTarget() && state.attachLocalAllocTag()) {
+      LLVM_DEBUG(llvm::dbgs().indent(2)
+                 << "Found reference to TARGET allocation at " << *op << "\n");
+      tag = state.getFuncTreeWithScope(func, scopeOp)
+                .targetDataTree.getTag(*name);
     } else if (name && state.attachLocalAllocTag()) {
       LLVM_DEBUG(llvm::dbgs().indent(2) << "Found reference to allocation "
                                         << name << " at " << *op << "\n");

flang/test/Driver/tco-test-gen.fir

@@ -77,13 +77,13 @@ func.func @_QPtest(%arg0: !fir.ref<i32> {fir.bindc_name = "num"}, %arg1: !fir.re
 // CHECK:           llvm.cond_br %[[VAL_17]], ^bb2, ^bb3
 // CHECK:         ^bb2:
 
-// AA:              llvm.store %[[VAL_15]], %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : i32, !llvm.ptr
+// AA:              llvm.store %[[VAL_15]], %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : i32, !llvm.ptr
 // NOAA:            llvm.store %[[VAL_15]], %{{.*}} : i32, !llvm.ptr
 
 // AA:              %[[VAL_18:.*]] = llvm.load %[[ARG0]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "dummy arg data/_QFtestEnum", members = {<#llvm.tbaa_type_desc<id = "dummy arg data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "dummy arg data/_QFtestEnum", members = {<#llvm.tbaa_type_desc<id = "dummy arg data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : !llvm.ptr -> i32
 // NOAA:            %[[VAL_18:.*]] = llvm.load %[[ARG0]] : !llvm.ptr -> i32
 
-// AA:              %[[VAL_19:.*]] = llvm.load %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : !llvm.ptr -> i32
+// AA:              %[[VAL_19:.*]] = llvm.load %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : !llvm.ptr -> i32
 // NOAA:            %[[VAL_19:.*]] = llvm.load %{{.*}} : !llvm.ptr -> i32
 
 // CHECK:           %[[VAL_20:.*]] = llvm.add %[[VAL_18]], %[[VAL_19]] : i32
@@ -92,15 +92,15 @@ func.func @_QPtest(%arg0: !fir.ref<i32> {fir.bindc_name = "num"}, %arg1: !fir.re
 
 // CHECK:           %[[VAL_21:.*]] = llvm.trunc %[[VAL_10]] : i64 to i32
 
-// AA:              %[[VAL_22:.*]] = llvm.load %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : !llvm.ptr -> i32
+// AA:              %[[VAL_22:.*]] = llvm.load %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : !llvm.ptr -> i32
 // NOAA:            %[[VAL_22:.*]] = llvm.load %{{.*}} : !llvm.ptr -> i32
 
 // CHECK:           %[[VAL_23:.*]] = llvm.add %[[VAL_22]], %[[VAL_21]] overflow<nsw> : i32
 // CHECK:           %[[VAL_24:.*]] = llvm.sub %[[VAL_16]], %{{.*}} : i64
 // CHECK:           llvm.br ^bb1(%[[VAL_23]], %[[VAL_24]] : i32, i64)
 // CHECK:         ^bb3:
 
-// AA:              llvm.store %[[VAL_15]], %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "target data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : i32, !llvm.ptr
+// AA:              llvm.store %[[VAL_15]], %[[VAL_1]] {tbaa = [#llvm.tbaa_tag<base_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, access_type = <id = "allocated data/_QFtestEi", members = {<#llvm.tbaa_type_desc<id = "allocated data", members = {<#llvm.tbaa_type_desc<id = "any data access", members = {<#llvm.tbaa_type_desc<id = "any access", members = {<#llvm.tbaa_root<id = "Flang function root _QPtest">, 0>}>, 0>}>, 0>}>, 0>}>, offset = 0>]} : i32, !llvm.ptr
 // NOAA:            llvm.store %[[VAL_15]], %{{.*}} : i32, !llvm.ptr
 
 // CHECK:           llvm.return

flang/test/Fir/tbaa-codegen2.fir

@@ -114,4 +114,3 @@ module attributes {fir.defaultkind = "a1c4d8i4l4r4", fir.kindmap = "", llvm.targ
 // CHECK: ![[TMP_DATA_ACCESS_TAG]] = !{![[TMP_DATA_ACCESS_TYPE:.*]], ![[TMP_DATA_ACCESS_TYPE]], i64 0}
 // CHECK: ![[TMP_DATA_ACCESS_TYPE]] = !{!"allocated data/", ![[TMP_ACCESS_TYPE:.*]], i64 0}
 // CHECK: ![[TMP_ACCESS_TYPE]] = !{!"allocated data", ![[TARGET_ACCESS_TAG:.*]], i64 0}
-// CHECK: ![[TARGET_ACCESS_TAG]] = !{!"target data", ![[DATA_ACCESS_TYPE]], i64 0}

flang/test/Transforms/tbaa-cray-pointer.fir

@@ -0,0 +1,43 @@
+// RUN: fir-opt -funsafe-cray-pointers --fir-add-alias-tags %s | FileCheck %s
+
+// Fortran source:
+// subroutine test()
+//   real :: a, b
+//   pointer(p, a)
+//   p = loc(b)
+//   b = 2
+// end subroutine
+
+// CHECK:      #[[TBAA_ROOT:.*]] = #llvm.tbaa_root<id = "Flang function root _QPtest">
+// CHECK-NEXT: #[[ANY_ACCESS:.*]] = #llvm.tbaa_type_desc<id = "any access", members = {<#[[TBAA_ROOT]], 0>}>
+// CHECK-NEXT: #[[ANY_DATA:.*]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[ANY_ACCESS]], 0>}>
+// CHECK-NEXT: #[[ANY_DATA_TAG:.*]] = #llvm.tbaa_tag<base_type = #[[ANY_DATA]], access_type = #[[ANY_DATA]], offset = 0>
+// CHECK-NEXT: #[[ALLOCATED_DATA:.*]] = #llvm.tbaa_type_desc<id = "allocated data", members = {<#[[ANY_DATA]], 0>}>
+// CHECK-NEXT: #[[B:.*]] = #llvm.tbaa_type_desc<id = "allocated data/_QFtestEb", members = {<#[[ALLOCATED_DATA]], 0>}>
+// CHECK-NEXT: #[[B_TAG:.*]] = #llvm.tbaa_tag<base_type = #[[B]], access_type = #[[B]], offset = 0>
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<!llvm.ptr<270> = dense<32> : vector<4xi64>, !llvm.ptr<271> = dense<32> : vector<4xi64>, !llvm.ptr<272> = dense<64> : vector<4xi64>, i8 = dense<[8, 32]> : vector<2xi64>, i16 = dense<[16, 32]> : vector<2xi64>, i64 = dense<64> : vector<2xi64>, i128 = dense<128> : vector<2xi64>, !llvm.ptr = dense<64> : vector<4xi64>, i1 = dense<8> : vector<2xi64>, i32 = dense<32> : vector<2xi64>, f16 = dense<16> : vector<2xi64>, f64 = dense<64> : vector<2xi64>, f128 = dense<128> : vector<2xi64>, "dlti.endianness" = "little", "dlti.mangling_mode" = "e", "dlti.legal_int_widths" = array<i32: 32, 64>, "dlti.stack_alignment" = 128 : i64, "dlti.function_pointer_alignment" = #dlti.function_pointer_alignment<32, function_dependent = true>>, fir.defaultkind = "a1c4d8i4l4r4", fir.kindmap = "", llvm.data_layout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"} {
+// CHECK-LABEL: func.func @_QPtest()
+  func.func @_QPtest() {
+    %cst = arith.constant 2.000000e+00 : f32
+    %0 = fir.alloca !fir.box<!fir.ptr<f32>>
+    %1 = fir.dummy_scope : !fir.dscope
+    %2 = fir.alloca i64 {bindc_name = "p", uniq_name = "_QFtestEp"}
+    %3 = fir.declare %2 {fortran_attrs = #fir.var_attrs<cray_pointer>, uniq_name = "_QFtestEp"} : (!fir.ref<i64>) -> !fir.ref<i64>
+    %4 = fir.alloca f32 {bindc_name = "b", uniq_name = "_QFtestEb"}
+    %5 = fir.declare %4 {uniq_name = "_QFtestEb"} : (!fir.ref<f32>) -> !fir.ref<f32>
+    %6 = fir.declare %0 {fortran_attrs = #fir.var_attrs<pointer, cray_pointee>, uniq_name = "_QFtestEa"} : (!fir.ref<!fir.box<!fir.ptr<f32>>>) -> !fir.ref<!fir.box<!fir.ptr<f32>>>
+    %7 = fir.zero_bits !fir.ptr<f32>
+    %8 = fir.embox %7 : (!fir.ptr<f32>) -> !fir.box<!fir.ptr<f32>>
+    fir.store %8 to %6 : !fir.ref<!fir.box<!fir.ptr<f32>>>
+// Descriptor tagged in codegen
+// CHECK: fir.store %{{.*}} to %{{.*}} : !fir.ref<!fir.box<!fir.ptr<f32>>
+    %9 = fir.convert %5 : (!fir.ref<f32>) -> i64
+    fir.store %9 to %3 : !fir.ref<i64>
+// CHECK: fir.store {{.*}} to {{.*}} {tbaa = [#[[ANY_DATA_TAG]]]} : !fir.ref<i64>
+    fir.store %cst to %5 : !fir.ref<f32>
+// CHECK: fir.store {{.*}} to {{.*}} {tbaa = [#[[B_TAG]]]} : !fir.ref<f32>
+    return
+  }
+}
+