[Flang][OpenMP] Fix for error in atomic read for different elements of the common symbol #80399

[chandankds]

Fixes issue #80399

[llvmbot]

@llvm/pr-subscribers-flang-openmp

@llvm/pr-subscribers-flang-semantics

Author: chandan singh (chandankds)

Changes

Fixes issue #80399

---

Full diff: https://github.com/llvm/llvm-project/pull/109265.diff

2 Files Affected:

• (modified) flang/lib/Semantics/check-omp-structure.cpp (+22-5)
• (added) flang/test/Semantics/OpenMP/omp-atomic-assignment-stmt-read.f90 (+43)

diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 643b713b32e29d..e90c8d2bdb3a46 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -1796,13 +1796,30 @@ inline void OmpStructureChecker::ErrIfLHSAndRHSSymbolsMatch(
   const auto *e{GetExpr(context_, expr)};
   const auto *v{GetExpr(context_, var)};
   if (e && v) {
-    auto vSyms{evaluate::GetSymbolVector(*v)};
-    const Symbol &varSymbol = vSyms.front();
+    const Symbol &varSymbol = evaluate::GetSymbolVector(*v).front();
     for (const Symbol &symbol : evaluate::GetSymbolVector(*e)) {
       if (varSymbol == symbol) {
-        context_.Say(expr.source,
-            "RHS expression on atomic assignment statement cannot access '%s'"_err_en_US,
-            var.GetSource().ToString());
+        const Fortran::common::Indirection<Fortran::parser::Designator>
+            *designator = std::get_if<
+                Fortran::common::Indirection<Fortran::parser::Designator>>(
+                &expr.u);
+        if (designator) {
+          auto *z{var.typedExpr.get()};
+          auto *c{expr.typedExpr.get()};
+          if (z->v == c->v) {
+            context_.Say(expr.source,
+                "RHS expression "
+                "on atomic assignment statement"
+                " cannot access '%s'"_err_en_US,
+                var.GetSource().ToString());
+          }
+        } else {
+          context_.Say(expr.source,
+              "RHS expression "
+              "on atomic assignment statement"
+              " cannot access '%s'"_err_en_US,
+              var.GetSource().ToString());
+        }
       }
     }
   }
diff --git a/flang/test/Semantics/OpenMP/omp-atomic-assignment-stmt-read.f90 b/flang/test/Semantics/OpenMP/omp-atomic-assignment-stmt-read.f90
new file mode 100644
index 00000000000000..2c8db296fc312e
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/omp-atomic-assignment-stmt-read.f90
@@ -0,0 +1,43 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+
+integer :: x, vv(2), xx(2)
+type t1
+  integer :: v,y,yy(2)
+end type t1
+type(t1)::t,tt(2)
+x=1
+xx=1
+vv=1
+t%y=1
+t%yy=1
+tt(1)%y=1
+tt(1)%yy=1
+tt(2)%v=1
+tt(2)%y=1
+tt(2)%yy=1
+
+!$omp atomic read
+  vv(1) = vv(2)
+!$omp atomic read
+  t%v = t%y
+!$omp atomic read
+  t%v = t%yy(1)
+!$omp atomic read
+  tt(1)%v = tt(1)%y
+!$omp atomic read
+  tt(1)%v = tt(2)%v
+!$omp atomic read
+  tt(1)%v = tt(1)%yy(1)
+!$omp atomic read
+  t%yy(2) = t%y
+!$omp atomic read
+  t%yy(2) = t%yy(1)
+!$omp atomic read
+  tt(1)%yy(2) = tt(1)%y
+!$omp atomic read
+  tt(1)%yy(2) = tt(1)%yy(1)
+!$omp atomic read
+  tt(1)%yy(2) = tt(2)%yy(2)
+!CHECK: pass
+print *,'pass'
+end

[kiranchandramohan]

We have some issues with using the front symbol of the SymbolVector in #108516 (review). Could you check whether it is OK here?

Some of the other comments in #108516 apply here as well regarding ToString() not required in the error messages.

[chandankds]

Reverted this unnecessary change and also confirmed front symbol of the SymbolVector is working as expected in this case.

[kiranchandramohan]

Can we have this in a single line so that it is easy to search for error messages?

[chandankds]

Done

[kiranchandramohan]

Can we have this in a single line so that it is easy to search for error messages?

[chandankds]

Done

[tblah]

What is this CHECK intended to do?

[chandankds]

Removed unnecessary check

[tblah]

You are not testing for any errors here, I think you are just testing that flang will compiler this file correctly. Using the test_errors.py script is incorrect because it allows flang to fail.

[chandankds]

Removed usage of test_errors.py from the test case.

[kiranchandramohan]

LGTM.