[flang][OpenMP] Map basic local specifiers to private clauses

Starts the effort to map `do concurrent` locality specifiers to OpenMP
clauses. This PR adds support for basic specifiers (no `init` or `copy`
regions yet).

Author: ergawy

flang/lib/Optimizer/OpenMP/DoConcurrentConversion.cpp

@@ -7,9 +7,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Optimizer/Builder/FIRBuilder.h"
+#include "flang/Optimizer/Builder/Todo.h"
 #include "flang/Optimizer/Dialect/FIROps.h"
 #include "flang/Optimizer/OpenMP/Passes.h"
 #include "flang/Optimizer/OpenMP/Utils.h"
+#include "flang/Support/OpenMP-utils.h"
 #include "mlir/Analysis/SliceAnalysis.h"
 #include "mlir/Dialect/OpenMP/OpenMPDialect.h"
 #include "mlir/IR/IRMapping.h"
@@ -308,10 +310,47 @@ class DoConcurrentConversion
               fir::DoConcurrentLoopOp loop, mlir::IRMapping &mapper,
               const mlir::omp::LoopNestOperands &clauseOps,
               bool isComposite) const {
+    mlir::omp::WsloopOperands wsloopClauseOps;
+
+    // For `local` (and `local_init`) opernads, emit corresponding `private`
+    // clauses and attach these clauses to the workshare loop.
+    if (!loop.getLocalOperands().empty())
+      for (auto [op, sym, arg] : llvm::zip_equal(
+               loop.getLocalOperands(),
+               loop.getLocalSymsAttr().getAsRange<mlir::SymbolRefAttr>(),
+               loop.getRegionLocalArgs())) {
+        auto localizer = mlir::SymbolTable::lookupNearestSymbolFrom<
+            fir::LocalitySpecifierOp>(loop, sym);
+        if (localizer.getLocalitySpecifierType() ==
+            fir::LocalitySpecifierType::LocalInit)
+          TODO(localizer.getLoc(),
+               "local_init conversion is not supported yet");
+
+        if (!localizer.getInitRegion().empty())
+          TODO(localizer.getLoc(),
+               "non-empty `init` regions are not supported yet");
+
+        auto oldIP = rewriter.saveInsertionPoint();
+        rewriter.setInsertionPointAfter(localizer);
+        auto privatizer = rewriter.create<mlir::omp::PrivateClauseOp>(
+            localizer.getLoc(), sym.getLeafReference().str() + ".omp",
+            localizer.getTypeAttr().getValue(),
+            mlir::omp::DataSharingClauseType::Private);
+        rewriter.restoreInsertionPoint(oldIP);
+
+        wsloopClauseOps.privateVars.push_back(op);
+        wsloopClauseOps.privateSyms.push_back(
+            mlir::SymbolRefAttr::get(privatizer));
+      }
 
-    auto wsloopOp = rewriter.create<mlir::omp::WsloopOp>(loop.getLoc());
+    auto wsloopOp =
+        rewriter.create<mlir::omp::WsloopOp>(loop.getLoc(), wsloopClauseOps);
     wsloopOp.setComposite(isComposite);
-    rewriter.createBlock(&wsloopOp.getRegion());
+
+    Fortran::common::openmp::EntryBlockArgs wsloopArgs;
+    wsloopArgs.priv.vars = wsloopClauseOps.privateVars;
+    Fortran::common::openmp::genEntryBlock(rewriter, wsloopArgs,
+                                           wsloopOp.getRegion());
 
     auto loopNestOp =
         rewriter.create<mlir::omp::LoopNestOp>(loop.getLoc(), clauseOps);
@@ -324,6 +363,18 @@ class DoConcurrentConversion
     rewriter.setInsertionPointToEnd(&loopNestOp.getRegion().back());
     rewriter.create<mlir::omp::YieldOp>(loop->getLoc());
 
+    // `local` region arguments are transferred/cloned from the `do concurrent`
+    // loop to the loopnest op when the region is cloned above. Instead, these
+    // region arguments should be on the workshare loop's region.
+    for (auto [wsloopArg, loopNestArg] :
+         llvm::zip_equal(wsloopOp.getRegion().getArguments(),
+                         loopNestOp.getRegion().getArguments().drop_front(
+                             clauseOps.loopLowerBounds.size())))
+      rewriter.replaceAllUsesWith(loopNestArg, wsloopArg);
+
+    for (unsigned i = 0; i < loop.getLocalVars().size(); ++i)
+      loopNestOp.getRegion().eraseArgument(clauseOps.loopLowerBounds.size());
+
     return loopNestOp;
   }
 

flang/test/Transforms/DoConcurrent/locality_specifiers_simple.mlir

@@ -0,0 +1,48 @@
+// Tests mapping `local` locality specifier to `private` clauses for a simple
+// case (not `init` or `copy` regions).
+
+// RUN: fir-opt --omp-do-concurrent-conversion="map-to=host" %s | FileCheck %s
+
+fir.local {type = local} @_QFlocal_spec_translationElocal_var_private_f32 : f32
+
+func.func @_QPlocal_spec_translation() {
+  %3 = fir.alloca f32 {bindc_name = "local_var", uniq_name = "_QFlocal_spec_translationElocal_var"}
+  %4:2 = hlfir.declare %3 {uniq_name = "_QFlocal_spec_translationElocal_var"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
+
+  %c4_i32 = arith.constant 4 : index
+  %c11_i32 = arith.constant 11 : index
+  %c1 = arith.constant 1 : index
+
+  fir.do_concurrent {
+    %7 = fir.alloca i32 {bindc_name = "i"}
+    %8:2 = hlfir.declare %7 {uniq_name = "_QFlocal_spec_translationEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+
+    fir.do_concurrent.loop (%arg0) = (%c4_i32) to (%c11_i32) step (%c1)
+      local(@_QFlocal_spec_translationElocal_var_private_f32 %4#0 -> %arg1 : !fir.ref<f32>) {
+      %9 = fir.convert %arg0 : (index) -> i32
+      fir.store %9 to %8#0 : !fir.ref<i32>
+
+      %10:2 = hlfir.declare %arg1 {uniq_name = "_QFlocal_spec_translationElocal_var"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
+      %cst = arith.constant 4.200000e+01 : f32
+      hlfir.assign %cst to %10#0 : f32, !fir.ref<f32>
+    }
+  }
+  return
+}
+
+// CHECK: omp.private {type = private} @[[PRIVATIZER:.*local_spec_translationElocal_var.*.omp]] : f32
+
+// CHECK: func.func @_QPlocal_spec_translation
+// CHECK:   %[[LOCAL_VAR:.*]] = fir.alloca f32 {bindc_name = "local_var", {{.*}}}
+// CHECK:   %[[LOCAL_VAR_DECL:.*]]:2 = hlfir.declare %[[LOCAL_VAR]]
+// CHECK:   omp.parallel {
+// CHECK:     omp.wsloop private(@[[PRIVATIZER]] %[[LOCAL_VAR_DECL]]#0 -> %[[LOCAL_ARG:.*]] : !fir.ref<f32>) {
+// CHECK:       omp.loop_nest {{.*}} {
+// CHECK:       %[[PRIV_DECL:.*]]:2 = hlfir.declare %[[LOCAL_ARG]]
+// CHECK:       %[[C42:.*]] = arith.constant
+// CHECK:       hlfir.assign %[[C42]] to %[[PRIV_DECL]]#0
+// CHECK:       omp.yield
+// CHECK:     }
+// CHECK:   }
+// CHECK:   omp.terminator
+// CHECK: }