[Flang][OpenMP] Use typed assignment in Atomic Write lowering

[kiranchandramohan]

Summary

Use typed assignment in Atomic Write lowering to better handle
type conversions of allowed types.

Note: We should make similar changes for other constructs in
later patches.

[NimishMishra]

Can you help me understand this a little bit? Typed assignment in this context is basically helping for an intrinsic conversion from an integer "0" to a floating point variable "r2". Is that it? And we should put up patches for the same in atomic.update and atomic.capture lowerings right?

[kiranchandramohan]

In D154163#4484146, @NimishMishra wrote:

Can you help me understand this a little bit? Typed assignment in this context is basically helping for an intrinsic conversion from an integer "0" to a floating point variable "r2". Is that it? And we should put up patches for the same in atomic.update and atomic.capture lowerings right?

Yes, that is correct. It helps in the conversion (or creating the constant with the correct type) here. Yes, we should doe the same for update and capture lowerings.

[NimishMishra]

Thank you @kiranchandramohan for the explanation. The patch LG.

flang/lib/Lower/OpenMP.cpp

 genOmpAtomicWrite(Fortran::lower::AbstractConverter &converter,
                   Fortran::lower::pft::Evaluation &eval,
                   const Fortran::parser::OmpAtomicWrite &atomicWrite) {
   // Get the value and address of atomic write operands.
   const Fortran::parser::OmpAtomicClauseList &rightHandClauseList =
       std::get<2>(atomicWrite.t);
   const Fortran::parser::OmpAtomicClauseList &leftHandClauseList =
       std::get<0>(atomicWrite.t);
-  const auto &assignmentStmtExpr =
-      std::get<Fortran::parser::Expr>(std::get<3>(atomicWrite.t).statement.t);
-  const auto &assignmentStmtVariable = std::get<Fortran::parser::Variable>(
-      std::get<3>(atomicWrite.t).statement.t);
+  const Fortran::parser::AssignmentStmt &stmt =
+      std::get<3>(atomicWrite.t).statement;
+  const Fortran::evaluate::Assignment &assign = *stmt.typedAssignment->v;
   Fortran::lower::StatementContext stmtCtx;
   // Get the value and address of atomic write operands.
-  mlir::Value rhs_expr = fir::getBase(converter.genExprValue(
-      *Fortran::semantics::GetExpr(assignmentStmtExpr), stmtCtx));
-  mlir::Value lhs_addr = fir::getBase(converter.genExprAddr(
-      *Fortran::semantics::GetExpr(assignmentStmtVariable), stmtCtx));
+  mlir::Value rhs_expr =
+      fir::getBase(converter.genExprValue(assign.rhs, stmtCtx));
+
+  mlir::Value lhs_addr =
+      fir::getBase(converter.genExprAddr(assign.lhs, stmtCtx));
   genOmpAtomicWriteStatement(converter, eval, lhs_addr, rhs_expr,
                              &leftHandClauseList, &rightHandClauseList);
 }
 
 static void genOmpAtomicRead(Fortran::lower::AbstractConverter &converter,
                              Fortran::lower::pft::Evaluation &eval,
                              const Fortran::parser::OmpAtomicRead &atomicRead) {
   // Get the address of atomic read operands.

flang/test/Lower/OpenMP/atomic-write.f90

subroutine atomic_write_pointer()
   integer, pointer :: x
 
   !$omp atomic write
     x = 1
 
   x = 2
 end
 
+!CHECK-LABEL: func.func @_QPatomic_write_typed_assign
+!CHECK: %[[VAR:.*]] = fir.alloca f32 {bindc_name = "r2", uniq_name = "{{.*}}r2"}
+!CHECK: %[[CST:.*]] = arith.constant 0.000000e+00 : f32
+!CHECK: omp.atomic.write %[[VAR]] = %[[CST]]   : !fir.ref<f32>, f32
+
+subroutine atomic_write_typed_assign
+  real :: r2
+  !$omp atomic write
+  r2 = 0
+end subroutine