[flang] Fixed fir.dummy_scope generation to work for TBAA. (#136382)

The nesting of fir.dummy_scope operations defines the roots
of the TBAA forest. If we do not generate fir.dummy_scope
in functions that do not have any dummy arguments, then
the globals accessed in the function and the dummy arguments
accessed by the callee may end up in different sub-trees
of the same root. The added tbaa-with-dummy-scope2.fir
demonstrates the issue.
diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
index b4d1197..1652a86 100644
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -5508,7 +5508,10 @@
     for (const Fortran::lower::CalleeInterface::PassedEntity &arg :
          callee.getPassedArguments())
       mapPassedEntity(arg);
-    if (lowerToHighLevelFIR() && !callee.getPassedArguments().empty()) {
+
+    // Always generate fir.dummy_scope even if there are no arguments.
+    // It is currently used to create proper TBAA forest.
+    if (lowerToHighLevelFIR()) {
       mlir::Value scopeOp = builder->create<fir::DummyScopeOp>(toLocation());
       setDummyArgsScope(scopeOp);
     }
diff --git a/flang/test/Driver/emit-mlir.f90 b/flang/test/Driver/emit-mlir.f90
index 2345a7c..de5a62d 100644
--- a/flang/test/Driver/emit-mlir.f90
+++ b/flang/test/Driver/emit-mlir.f90
@@ -13,6 +13,7 @@
 ! CHECK-SAME: dlti.dl_spec =
 ! CHECK-SAME: llvm.data_layout =
 ! CHECK-LABEL: func @_QQmain() {
+! CHECK-NEXT:  fir.dummy_scope
 ! CHECK-NEXT:  return
 ! CHECK-NEXT: }
 ! CHECK-NEXT: func.func private @_FortranAProgramStart(i32, !llvm.ptr, !llvm.ptr, !llvm.ptr)
diff --git a/flang/test/Lower/HLFIR/calls-f77.f90 b/flang/test/Lower/HLFIR/calls-f77.f90
index 64b90b8..450f881 100644
--- a/flang/test/Lower/HLFIR/calls-f77.f90
+++ b/flang/test/Lower/HLFIR/calls-f77.f90
@@ -9,6 +9,7 @@
   call void()
 end subroutine
 ! CHECK-LABEL: func.func @_QPcall_no_arg() {
+! CHECK-NEXT:  fir.dummy_scope
 ! CHECK-NEXT:  fir.call @_QPvoid() fastmath<contract> : () -> ()
 ! CHECK-NEXT:  return
 
diff --git a/flang/test/Lower/HLFIR/dummy-scope.f90 b/flang/test/Lower/HLFIR/dummy-scope.f90
new file mode 100644
index 0000000..4b1a332
--- /dev/null
+++ b/flang/test/Lower/HLFIR/dummy-scope.f90
@@ -0,0 +1,52 @@
+! RUN: bbc -emit-hlfir %s -o - | FileCheck %s
+
+! Test fir.dummy_scope assignment to argument x
+subroutine sub_arg(x)
+  integer :: x
+end subroutine sub_arg
+! CHECK-LABEL:   func.func @_QPsub_arg(
+! CHECK-SAME:                          %[[VAL_0:[0-9]+|[a-zA-Z$._-][a-zA-Z0-9$._-]*]]: !fir.ref<i32> {fir.bindc_name = "x"}) {
+! CHECK:           %[[VAL_1:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[VAL_2:.*]]:2 = hlfir.declare %[[VAL_0]] dummy_scope %[[VAL_1]] {uniq_name = "_QFsub_argEx"} : (!fir.ref<i32>, !fir.dscope) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:           return
+! CHECK:         }
+
+! Test fir.dummy_scope is created even when there are no arguments.
+subroutine sub_noarg
+end subroutine sub_noarg
+! CHECK-LABEL:   func.func @_QPsub_noarg() {
+! CHECK:           %[[VAL_0:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           return
+! CHECK:         }
+
+! Test fir.dummy_scope assignment to argument x
+function func_arg(x)
+  integer :: x, func_arg
+  func_arg = x
+end function func_arg
+! CHECK-LABEL:   func.func @_QPfunc_arg(
+! CHECK-SAME:                           %[[VAL_0:[0-9]+|[a-zA-Z$._-][a-zA-Z0-9$._-]*]]: !fir.ref<i32> {fir.bindc_name = "x"}) -> i32 {
+! CHECK:           %[[VAL_1:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[VAL_2:.*]] = fir.alloca i32 {bindc_name = "func_arg", uniq_name = "_QFfunc_argEfunc_arg"}
+! CHECK:           %[[VAL_3:.*]]:2 = hlfir.declare %[[VAL_2]] {uniq_name = "_QFfunc_argEfunc_arg"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:           %[[VAL_4:.*]]:2 = hlfir.declare %[[VAL_0]] dummy_scope %[[VAL_1]] {uniq_name = "_QFfunc_argEx"} : (!fir.ref<i32>, !fir.dscope) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:           %[[VAL_5:.*]] = fir.load %[[VAL_4]]#0 : !fir.ref<i32>
+! CHECK:           hlfir.assign %[[VAL_5]] to %[[VAL_3]]#0 : i32, !fir.ref<i32>
+! CHECK:           %[[VAL_6:.*]] = fir.load %[[VAL_3]]#0 : !fir.ref<i32>
+! CHECK:           return %[[VAL_6]] : i32
+! CHECK:         }
+
+! Test fir.dummy_scope is created even when there are no arguments.
+function func_noarg
+  integer :: func_noarg
+  func_noarg = 1
+end function func_noarg
+! CHECK-LABEL:   func.func @_QPfunc_noarg() -> i32 {
+! CHECK:           %[[VAL_0:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[VAL_1:.*]] = fir.alloca i32 {bindc_name = "func_noarg", uniq_name = "_QFfunc_noargEfunc_noarg"}
+! CHECK:           %[[VAL_2:.*]]:2 = hlfir.declare %[[VAL_1]] {uniq_name = "_QFfunc_noargEfunc_noarg"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:           %[[VAL_3:.*]] = arith.constant 1 : i32
+! CHECK:           hlfir.assign %[[VAL_3]] to %[[VAL_2]]#0 : i32, !fir.ref<i32>
+! CHECK:           %[[VAL_4:.*]] = fir.load %[[VAL_2]]#0 : !fir.ref<i32>
+! CHECK:           return %[[VAL_4]] : i32
+! CHECK:         }
diff --git a/flang/test/Lower/OpenMP/real10.f90 b/flang/test/Lower/OpenMP/real10.f90
index 0a092eb..a31d2ac 100644
--- a/flang/test/Lower/OpenMP/real10.f90
+++ b/flang/test/Lower/OpenMP/real10.f90
@@ -2,7 +2,7 @@
 
 !RUN: %flang_fc1 -emit-hlfir -fopenmp -triple amdgcn -fopenmp -fopenmp-is-target-device -o - %s | FileCheck %s
 
-!CHECK: hlfir.declare %0 {uniq_name = "_QFEx"} : (!fir.ref<f80>) -> (!fir.ref<f80>, !fir.ref<f80>)
+!CHECK: hlfir.declare %{{.*}} {uniq_name = "_QFEx"} : (!fir.ref<f80>) -> (!fir.ref<f80>, !fir.ref<f80>)
 
 program p
   real(10) :: x
diff --git a/flang/test/Lower/main_location.f90 b/flang/test/Lower/main_location.f90
index db63339..73943f8 100644
--- a/flang/test/Lower/main_location.f90
+++ b/flang/test/Lower/main_location.f90
@@ -12,6 +12,7 @@
 end
 
 ! TEST1: func.func @_QQmain() {
+! TEST1-NEXT: fir.dummy_scope : !fir.dscope loc("{{.*}}test1.f90":1:1)
 ! TEST1-NEXT: return loc("{{.*}}test1.f90":3:1)
 ! TEST1-NEXT: } loc("{{.*}}test1.f90":1:1)
 
@@ -22,5 +23,6 @@
 end program
 
 ! TEST2: func.func @_QQmain() {
+! TEST2-NEXT: fir.dummy_scope : !fir.dscope loc("{{.*}}test2.f90":2:1)
 ! TEST2-NEXT: return loc("{{.*}}test2.f90":4:1)
 ! TEST2-NEXT: } loc("{{.*}}test2.f90":2:1)
diff --git a/flang/test/Transforms/tbaa-with-dummy-scope2.fir b/flang/test/Transforms/tbaa-with-dummy-scope2.fir
new file mode 100644
index 0000000..a28b4d5
--- /dev/null
+++ b/flang/test/Transforms/tbaa-with-dummy-scope2.fir
@@ -0,0 +1,106 @@
+// RUN: fir-opt --fir-add-alias-tags --split-input-file %s | FileCheck %s
+
+// This test demonstrates the need for fir.dummy_scope even
+// when a function does not have dummy arguments.
+//
+// The original source is:
+// module m
+//   integer :: glob
+// end module m
+// subroutine test1
+//   use m
+//   call inner(glob)
+//   glob = 2
+// contains
+//   subroutine inner(x)
+//     integer :: x
+//     integer :: y
+//     y = 1
+//     x = y
+//   end subroutine inner
+// end subroutine test1
+//
+// 'inner' function is manually inlined in FIR.
+// When fir.dummy_scope is missing, TBAA tags for glob and x
+// are placed into the same TBAA root. Since glob is a global
+// and x is a dummy argument, TBAA ends up reporting no-alias
+// for them, which is incorrect.
+func.func @_QPtest1() attributes {noinline} {
+  %c1_i32 = arith.constant 1 : i32
+  %c2_i32 = arith.constant 2 : i32
+  %0 = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFtest1FinnerEy"}
+  %1 = fir.address_of(@_QMmEglob) : !fir.ref<i32>
+  %2 = fir.declare %1 {uniq_name = "_QMmEglob"} : (!fir.ref<i32>) -> !fir.ref<i32>
+  %3 = fir.dummy_scope : !fir.dscope
+  %4 = fir.declare %2 dummy_scope %3 {uniq_name = "_QFtest1FinnerEx"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
+  %5 = fir.declare %0 {uniq_name = "_QFtest1FinnerEy"} : (!fir.ref<i32>) -> !fir.ref<i32>
+  fir.store %c1_i32 to %5 : !fir.ref<i32>
+  %6 = fir.load %5 : !fir.ref<i32>
+  fir.store %6 to %4 : !fir.ref<i32>
+  fir.store %c2_i32 to %2 : !fir.ref<i32>
+  return
+}
+// CHECK: #[[$ATTR_0:.+]] = #llvm.tbaa_root<id = "Flang function root _QPtest1">
+// CHECK: #[[$ATTR_1:.+]] = #llvm.tbaa_type_desc<id = "any access", members = {<#[[$ATTR_0]], 0>}>
+// CHECK: #[[$ATTR_2:.+]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[$ATTR_1]], 0>}>
+// CHECK: #[[$ATTR_3:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data", members = {<#[[$ATTR_2]], 0>}>
+// CHECK: #[[$ATTR_4:.+]] = #llvm.tbaa_type_desc<id = "global data", members = {<#[[$ATTR_2]], 0>}>
+// CHECK: #[[$ATTR_5:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data/_QFtest1FinnerEx", members = {<#[[$ATTR_3]], 0>}>
+// CHECK: #[[$ATTR_6:.+]] = #llvm.tbaa_type_desc<id = "global data/_QMmEglob", members = {<#[[$ATTR_4]], 0>}>
+// CHECK: #[[$ATTR_7:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_5]], access_type = #[[$ATTR_5]], offset = 0>
+// CHECK: #[[$ATTR_8:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_6]], access_type = #[[$ATTR_6]], offset = 0>
+// CHECK-LABEL:   func.func @_QPtest1() attributes {noinline} {
+// CHECK:           %[[VAL_2:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFtest1FinnerEy"}
+// CHECK:           %[[VAL_3:.*]] = fir.address_of(@_QMmEglob) : !fir.ref<i32>
+// CHECK:           %[[VAL_4:.*]] = fir.declare %[[VAL_3]] {uniq_name = "_QMmEglob"} : (!fir.ref<i32>) -> !fir.ref<i32>
+// CHECK:           %[[VAL_5:.*]] = fir.dummy_scope : !fir.dscope
+// CHECK:           %[[VAL_6:.*]] = fir.declare %[[VAL_4]] dummy_scope %[[VAL_5]] {uniq_name = "_QFtest1FinnerEx"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
+// CHECK:           %[[VAL_7:.*]] = fir.declare %[[VAL_2]] {uniq_name = "_QFtest1FinnerEy"} : (!fir.ref<i32>) -> !fir.ref<i32>
+// CHECK:           fir.store %{{.*}} to %[[VAL_7]] : !fir.ref<i32>
+// CHECK:           %[[VAL_8:.*]] = fir.load %[[VAL_7]] : !fir.ref<i32>
+// CHECK:           fir.store %[[VAL_8]] to %[[VAL_6]] {tbaa = [#[[$ATTR_7]]]} : !fir.ref<i32>
+// CHECK:           fir.store %{{.*}} to %[[VAL_4]] {tbaa = [#[[$ATTR_8]]]} : !fir.ref<i32>
+
+// -----
+
+// This test has fir.dummy_scope in place, and TBAA is correct.
+func.func @_QPtest2() attributes {noinline} {
+  %c1_i32 = arith.constant 1 : i32
+  %c2_i32 = arith.constant 2 : i32
+  %0 = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFtest2FinnerEy"}
+  %test_dummy_scope = fir.dummy_scope : !fir.dscope
+  %1 = fir.address_of(@_QMmEglob) : !fir.ref<i32>
+  %2 = fir.declare %1 {uniq_name = "_QMmEglob"} : (!fir.ref<i32>) -> !fir.ref<i32>
+  %3 = fir.dummy_scope : !fir.dscope
+  %4 = fir.declare %2 dummy_scope %3 {uniq_name = "_QFtest2FinnerEx"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
+  %5 = fir.declare %0 {uniq_name = "_QFtest2FinnerEy"} : (!fir.ref<i32>) -> !fir.ref<i32>
+  fir.store %c1_i32 to %5 : !fir.ref<i32>
+  %6 = fir.load %5 : !fir.ref<i32>
+  fir.store %6 to %4 : !fir.ref<i32>
+  fir.store %c2_i32 to %2 : !fir.ref<i32>
+  return
+}
+// CHECK: #[[$ATTR_0:.+]] = #llvm.tbaa_root<id = "Flang function root _QPtest2 - Scope 1">
+// CHECK: #[[$ATTR_1:.+]] = #llvm.tbaa_root<id = "Flang function root _QPtest2">
+// CHECK: #[[$ATTR_2:.+]] = #llvm.tbaa_type_desc<id = "any access", members = {<#[[$ATTR_0]], 0>}>
+// CHECK: #[[$ATTR_3:.+]] = #llvm.tbaa_type_desc<id = "any access", members = {<#[[$ATTR_1]], 0>}>
+// CHECK: #[[$ATTR_4:.+]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[$ATTR_2]], 0>}>
+// CHECK: #[[$ATTR_5:.+]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[$ATTR_3]], 0>}>
+// CHECK: #[[$ATTR_6:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data", members = {<#[[$ATTR_4]], 0>}>
+// CHECK: #[[$ATTR_7:.+]] = #llvm.tbaa_type_desc<id = "global data", members = {<#[[$ATTR_5]], 0>}>
+// CHECK: #[[$ATTR_8:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data/_QFtest2FinnerEx", members = {<#[[$ATTR_6]], 0>}>
+// CHECK: #[[$ATTR_9:.+]] = #llvm.tbaa_type_desc<id = "global data/_QMmEglob", members = {<#[[$ATTR_7]], 0>}>
+// CHECK: #[[$ATTR_10:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_8]], access_type = #[[$ATTR_8]], offset = 0>
+// CHECK: #[[$ATTR_11:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_9]], access_type = #[[$ATTR_9]], offset = 0>
+// CHECK-LABEL:   func.func @_QPtest2() attributes {noinline} {
+// CHECK:           %[[VAL_2:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFtest2FinnerEy"}
+// CHECK:           %[[VAL_3:.*]] = fir.dummy_scope : !fir.dscope
+// CHECK:           %[[VAL_4:.*]] = fir.address_of(@_QMmEglob) : !fir.ref<i32>
+// CHECK:           %[[VAL_5:.*]] = fir.declare %[[VAL_4]] {uniq_name = "_QMmEglob"} : (!fir.ref<i32>) -> !fir.ref<i32>
+// CHECK:           %[[VAL_6:.*]] = fir.dummy_scope : !fir.dscope
+// CHECK:           %[[VAL_7:.*]] = fir.declare %[[VAL_5]] dummy_scope %[[VAL_6]] {uniq_name = "_QFtest2FinnerEx"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
+// CHECK:           %[[VAL_8:.*]] = fir.declare %[[VAL_2]] {uniq_name = "_QFtest2FinnerEy"} : (!fir.ref<i32>) -> !fir.ref<i32>
+// CHECK:           fir.store %{{.*}} to %[[VAL_8]] : !fir.ref<i32>
+// CHECK:           %[[VAL_9:.*]] = fir.load %[[VAL_8]] : !fir.ref<i32>
+// CHECK:           fir.store %[[VAL_9]] to %[[VAL_7]] {tbaa = [#[[$ATTR_10]]]} : !fir.ref<i32>
+// CHECK:           fir.store %{{.*}} to %[[VAL_5]] {tbaa = [#[[$ATTR_11]]]} : !fir.ref<i32>