[flang][OpenMP] Fix the types of worksharing-loop variables

[peixin]

Summary

The types of lower bound, upper bound, and step are converted into the
type of the loop variable if necessary. OpenMP runtime requires 32-bit
or 64-bit loop variables. OpenMP loop iteration variable cannot have
more than 64 bits size and will be narrowed.

This patch is part of upstreaming code from the fir-dev branch of
https://github.com/flang-compiler/f18-llvm-project. (#1256)

Co-authored-by: kiranchandramohan <[e-mail]>

[peixin]

Fix the IR check of test case.

[shraiysh]

Thanks for this. LGTM. Minor comments.

flang/lib/Lower/OpenMP.cpp

129

nit: make this >64 maybe?

flang/test/Lower/OpenMP/omp-wsloop-variable.f90

31

Can we please add the same testcase without collapse? I wanted to make sure that the outer bounds in that case change to i32 and inner change to i64 and they do not interfere with each other.

[peixin]

Rebase and address comments.

flang/lib/Lower/OpenMP.cpp

129

Thanks for the notice. Fixed.

flang/test/Lower/OpenMP/omp-wsloop-variable.f90

31

Added the test case.

[kiranchandramohan]

LGTM.

[peixin]

Rebase and fix one clang format

[peixin]

rebase before land

flang/lib/Lower/OpenMP.cpp

std::visit(Fortran::common::visitors{
                    },
                    [&](const Fortran::parser::Name &name) {
                      addOperands(*name.symbol);
                    }},
                ompObject.u);
   }
 }
 
+static mlir::Type getLoopVarType(Fortran::lower::AbstractConverter &converter,
+                                 std::size_t loopVarTypeSize) {
+  // OpenMP runtime requires 32-bit or 64-bit loop variables.
+  loopVarTypeSize = loopVarTypeSize * 8;
+  if (loopVarTypeSize < 32) {
+    loopVarTypeSize = 32;
+  } else if (loopVarTypeSize == 128) {
+    loopVarTypeSize = 64;
+    mlir::emitWarning(converter.getCurrentLocation(),
+                      "OpenMP loop iteration variable cannot have more than 64 "
+                      "bits size and will be narrowed into 64 bits.");
+  }
+  assert((loopVarTypeSize == 32 || loopVarTypeSize == 64) &&
+         "OpenMP loop iteration variable size must be transformed into 32-bit "
+         "or 64-bit");
+  return converter.getFirOpBuilder().getIntegerType(loopVarTypeSize);
+}
+
 /// Create the body (block) for an OpenMP Operation.
 ///
 /// \param [in]    op - the operation the body belongs to.
 /// \param [inout] converter - converter to use for the clauses.
 /// \param [in]    loc - location in source code.
 /// \oaran [in]    clauses - list of clauses to process.
 /// \param [in]    args - block arguments (induction variable[s]) for the
 ////                      region.
 /// \param [in]    outerCombined - is this an outer operation - prevents
 ///                                privatization.
 template <typename Op>
 static void
 createBodyOfOp(Op &op, Fortran::lower::AbstractConverter &converter,
                mlir::Location &loc,
                const Fortran::parser::OmpClauseList *clauses = nullptr,
                const SmallVector<const Fortran::semantics::Symbol *> &args = {},
                bool outerCombined = false) {
   fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
   // If arguments for the region are provided then create the block with those
   // arguments. Also update the symbol's address with the mlir argument values.
   // e.g. For loops the arguments are the induction variable. And all further
   // uses of the induction variable should use this mlir value.
   if (args.size()) {
+    std::size_t loopVarTypeSize = 0;
+    for (const Fortran::semantics::Symbol *arg : args)
+      loopVarTypeSize = std::max(loopVarTypeSize, arg->GetUltimate().size());
+    mlir::Type loopVarType = getLoopVarType(converter, loopVarTypeSize);
     SmallVector<Type> tiv;
     SmallVector<Location> locs;
-    int argIndex = 0;
-    for (auto &arg : args) {
-      tiv.push_back(converter.genType(*arg));
+    for (int i = 0; i < (int)args.size(); i++) {
+      tiv.push_back(loopVarType);
       locs.push_back(loc);
     }
     firOpBuilder.createBlock(&op.getRegion(), {}, tiv, locs);
-    for (auto &arg : args) {
+    int argIndex = 0;
+    for (const Fortran::semantics::Symbol *arg : args) {
       fir::ExtendedValue exval = op.getRegion().front().getArgument(argIndex);
       converter.bindSymbol(*arg, exval);
       argIndex++;
     }
   } else {
     firOpBuilder.createBlock(&op.getRegion());
   }
   auto &block = op.getRegion().back();
const auto &wsLoopOpClauseList = std::get<Fortran::parser::OmpClauseList>(
       std::get<Fortran::parser::OmpBeginLoopDirective>(loopConstruct.t).t);
   if (llvm::omp::OMPD_do !=
       std::get<Fortran::parser::OmpLoopDirective>(
           std::get<Fortran::parser::OmpBeginLoopDirective>(loopConstruct.t).t)
           .v) {
     TODO(converter.getCurrentLocation(), "Combined worksharing loop construct");
   }
 
-  int64_t collapseValue = Fortran::lower::getCollapseValue(wsLoopOpClauseList);
-
   // Collect the loops to collapse.
   auto *doConstructEval = &eval.getFirstNestedEvaluation();
 
+  std::int64_t collapseValue =
+      Fortran::lower::getCollapseValue(wsLoopOpClauseList);
+  std::size_t loopVarTypeSize = 0;
   SmallVector<const Fortran::semantics::Symbol *> iv;
   do {
     auto *doLoop = &doConstructEval->getFirstNestedEvaluation();
     auto *doStmt = doLoop->getIf<Fortran::parser::NonLabelDoStmt>();
     assert(doStmt && "Expected do loop to be in the nested evaluation");
     const auto &loopControl =
         std::get<std::optional<Fortran::parser::LoopControl>>(doStmt->t);
     const Fortran::parser::LoopControl::Bounds *bounds =
         std::get_if<Fortran::parser::LoopControl::Bounds>(&loopControl->u);
     if (bounds) {
       Fortran::lower::StatementContext stmtCtx;
       lowerBound.push_back(fir::getBase(converter.genExprValue(
           *Fortran::semantics::GetExpr(bounds->lower), stmtCtx)));
       upperBound.push_back(fir::getBase(converter.genExprValue(
           *Fortran::semantics::GetExpr(bounds->upper), stmtCtx)));
       if (bounds->step) {
         step.push_back(fir::getBase(converter.genExprValue(
             *Fortran::semantics::GetExpr(bounds->step), stmtCtx)));
       } else { // If `step` is not present, assume it as `1`.
         step.push_back(firOpBuilder.createIntegerConstant(
             currentLocation, firOpBuilder.getIntegerType(32), 1));
       }
       iv.push_back(bounds->name.thing.symbol);
+      loopVarTypeSize = std::max(
+          loopVarTypeSize, bounds->name.thing.symbol->GetUltimate().size());
     }
 
     collapseValue--;
     doConstructEval =
         &*std::next(doConstructEval->getNestedEvaluations().begin());
   } while (collapseValue > 0);
 
+  // The types of lower bound, upper bound, and step are converted into the
+  // type of the loop variable if necessary.
+  mlir::Type loopVarType = getLoopVarType(converter, loopVarTypeSize);
+  for (unsigned it = 0; it < (unsigned)lowerBound.size(); it++) {
+    lowerBound[it] = firOpBuilder.createConvert(currentLocation, loopVarType,
+                                                lowerBound[it]);
+    upperBound[it] = firOpBuilder.createConvert(currentLocation, loopVarType,
+                                                upperBound[it]);
+    step[it] =
+        firOpBuilder.createConvert(currentLocation, loopVarType, step[it]);
+  }
+
   // FIXME: Add support for following clauses:
   // 1. linear
   // 2. order
   // 3. schedule (with chunk)
   auto wsLoopOp = firOpBuilder.create<mlir::omp::WsLoopOp>(
       currentLocation, lowerBound, upperBound, step, linearVars, linearStepVars,
       reductionVars, /*reductions=*/nullptr,
       scheduleClauseOperand.dyn_cast_or_null<omp::ClauseScheduleKindAttr>(),

flang/test/Lower/OpenMP/omp-wsloop-variable.f90

+! This test checks lowering of OpenMP DO Directive(Worksharing) for different
+! types of loop iteration variable, lower bound, upper bound, and step.
+
+!REQUIRES: shell
+!RUN: bbc -fopenmp -emit-fir %s -o - 2>&1 | FileCheck %s
+
+program wsloop_variable
+  integer(kind=1) :: i1_lb, i1_ub
+  integer(kind=2) :: i2, i2_ub, i2_s
+  integer(kind=4) :: i4_s
+  integer(kind=8) :: i8, i8_s
+  integer(kind=16) :: i16, i16_lb
+  real :: x
+
+!CHECK:  OpenMP loop iteration variable cannot have more than 64 bits size and will be narrowed into 64 bits.
+
+!CHECK:  [[TMP0:%.*]] = arith.constant 1 : i32
+!CHECK:  [[TMP1:%.*]] = arith.constant 100 : i32
+!CHECK:  [[TMP2:%.*]] = fir.convert [[TMP0]] : (i32) -> i64
+!CHECK:  [[TMP3:%.*]] = fir.convert %{{.*}} : (i8) -> i64
+!CHECK:  [[TMP4:%.*]] = fir.convert %{{.*}} : (i16) -> i64
+!CHECK:  [[TMP5:%.*]] = fir.convert %{{.*}} : (i128) -> i64
+!CHECK:  [[TMP6:%.*]] = fir.convert [[TMP1]] : (i32) -> i64
+!CHECK:  [[TMP7:%.*]] = fir.convert %{{.*}} : (i32) -> i64
+!CHECK:  omp.wsloop collapse(2) for ([[TMP8:%.*]], [[TMP9:%.*]]) : i64 = ([[TMP2]], [[TMP5]]) to ([[TMP3]], [[TMP6]]) inclusive step ([[TMP4]], [[TMP7]]) {
+!CHECK:    [[TMP10:%.*]] = arith.addi [[TMP8]], [[TMP9]] : i64
+!CHECK:    [[TMP11:%.*]] = fir.convert [[TMP10]] : (i64) -> f32
+!CHECK:    fir.store [[TMP11]] to %{{.*}} : !fir.ref<f32>
+!CHECK:    omp.yield
+!CHECK:  }
+  !$omp do collapse(2)
+  do i2 = 1, i1_ub, i2_s
+    do i8 = i16_lb, 100, i4_s
+      x = i2 + i8
+    end do
+  end do
+  !$omp end do
+
+!CHECK:  [[TMP12:%.*]] = arith.constant 1 : i32
+!CHECK:  [[TMP13:%.*]] = fir.convert %{{.*}} : (i8) -> i32
+!CHECK:  [[TMP14:%.*]] = fir.convert %{{.*}} : (i64) -> i32
+!CHECK:  omp.wsloop for ([[TMP15:%.*]]) : i32 = ([[TMP12]]) to ([[TMP13]]) inclusive step ([[TMP14]])  {
+!CHECK:    [[TMP16:%.*]] = fir.convert [[TMP15]] : (i32) -> f32
+!CHECK:    fir.store [[TMP16]] to %{{.*}} : !fir.ref<f32>
+!CHECK:    omp.yield
+!CHECK:  }
+  !$omp do
+  do i2 = 1, i1_ub, i8_s
+    x = i2
+  end do
+  !$omp end do
+
+!CHECK:  [[TMP17:%.*]] = fir.convert %{{.*}} : (i8) -> i64
+!CHECK:  [[TMP18:%.*]] = fir.convert %{{.*}} : (i16) -> i64
+!CHECK:  [[TMP19:%.*]] = fir.convert %{{.*}} : (i32) -> i64
+!CHECK:  omp.wsloop for ([[TMP20:%.*]]) : i64 = ([[TMP17]]) to ([[TMP18]]) inclusive step ([[TMP19]])  {
+!CHECK:    [[TMP21:%.*]] = fir.convert [[TMP20]] : (i64) -> f32
+!CHECK:    fir.store [[TMP21]] to %{{.*}} : !fir.ref<f32>
+!CHECK:    omp.yield
+!CHECK:  }
+  !$omp do
+  do i16 = i1_lb, i2_ub, i4_s
+    x = i16
+  end do
+  !$omp end do
+
+end program wsloop_variable