[WIP] Delayed privatization.

flang/include/flang/Lower/SymbolMap.h

@@ -312,6 +312,7 @@ class SymMap {
   lookupVariableDefinition(semantics::SymbolRef sym) {
     if (auto symBox = lookupSymbol(sym))
       return symBox.getIfFortranVariableOpInterface();
+
     return std::nullopt;
   }
 

flang/lib/Lower/Bridge.cpp

@@ -1052,7 +1052,10 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       if (sym.detailsIf<Fortran::semantics::CommonBlockDetails>())
         return symMap->lookupSymbol(sym);
 
-      return {};
+      // With delayed privatization, Fortran symbols might now be mapped to
+      // simple `mlir::Value`s (arguments to the `omp.private` ops in this
+      // case). Therefore, it is possible that none of the above cases applies.
+      // return {};
     }
     if (Fortran::lower::SymbolBox v = symMap->lookupSymbol(sym))
       return v;

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -3505,6 +3505,18 @@ struct ZeroOpConversion : public FIROpConversion<fir::ZeroOp> {
   }
 };
 
+class DeclareOpConversion : public FIROpConversion<fir::DeclareOp> {
+public:
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::DeclareOp declareOp, OpAdaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    rewriter.replaceOp(declareOp, declareOp.getMemref());
+    return mlir::success();
+  }
+};
+
 /// `fir.unreachable` --> `llvm.unreachable`
 struct UnreachableOpConversion : public FIROpConversion<fir::UnreachableOp> {
   using FIROpConversion::FIROpConversion;
@@ -3856,6 +3868,7 @@ class RenameMSVCLibmFuncs
     return mlir::success();
   }
 };
+
 } // namespace
 
 namespace {
@@ -3949,7 +3962,7 @@ class FIRToLLVMLowering
         UnboxCharOpConversion, UnboxProcOpConversion, UndefOpConversion,
         UnreachableOpConversion, UnrealizedConversionCastOpConversion,
         XArrayCoorOpConversion, XEmboxOpConversion, XReboxOpConversion,
-        ZeroOpConversion>(typeConverter, options);
+        ZeroOpConversion, DeclareOpConversion>(typeConverter, options);
     mlir::populateFuncToLLVMConversionPatterns(typeConverter, pattern);
     mlir::populateOpenMPToLLVMConversionPatterns(typeConverter, pattern);
     mlir::arith::populateArithToLLVMConversionPatterns(typeConverter, pattern);
@@ -4002,7 +4015,8 @@ class FIRToLLVMLowering
       signalPassFailure();
     }
 
-    // Run pass to add comdats to functions that have weak linkage on relevant platforms
+    // Run pass to add comdats to functions that have weak linkage on relevant
+    // platforms
     if (fir::getTargetTriple(mod).supportsCOMDAT()) {
       mlir::OpPassManager comdatPM("builtin.module");
       comdatPM.addPass(mlir::LLVM::createLLVMAddComdats());

flang/test/Lower/OpenMP/FIR/delayed_privatization.f90

@@ -3,6 +3,7 @@
 ! RUN: bbc -fopenmp -emit-fir --openmp-enable-delayed-privatization -hlfir=false %s -o - 
 
 subroutine delayed_privatization()
+  implicit none
   integer :: var1
   integer :: var2
 

flang/test/Lower/OpenMP/FIR/delayed_privatization_hlfir.f90

@@ -0,0 +1,71 @@
+! TODO Convert this file into a bunch of lit tests for each conversion step.
+
+! RUN: bbc -fopenmp -emit-hlfir --openmp-enable-delayed-privatization %s -o - 
+
+subroutine delayed_privatization()
+  implicit none
+  integer :: var1
+  integer :: var2
+
+  var1 = 111
+  var2 = 222
+
+!$OMP PARALLEL FIRSTPRIVATE(var1, var2)
+  var1 = var1 + var2 + 2
+!$OMP END PARALLEL
+
+end subroutine
+
+
+! -----------------------------------------
+! ## This is what flang emits with the PoC:
+! -----------------------------------------
+!
+! ----------------------------
+! ### Conversion to HLFIR + OMP:
+! ----------------------------
+!module {
+!  func.func @_QPdelayed_privatization() {
+!    %0 = fir.alloca i32 {bindc_name = "var1", uniq_name = "_QFdelayed_privatizationEvar1"}
+!    %1:2 = hlfir.declare %0 {uniq_name = "_QFdelayed_privatizationEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!    %2 = fir.alloca i32 {bindc_name = "var2", uniq_name = "_QFdelayed_privatizationEvar2"}
+!    %3:2 = hlfir.declare %2 {uniq_name = "_QFdelayed_privatizationEvar2"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!    %c111_i32 = arith.constant 111 : i32
+!    hlfir.assign %c111_i32 to %1#0 : i32, !fir.ref<i32>
+!    %c222_i32 = arith.constant 222 : i32
+!    hlfir.assign %c222_i32 to %3#0 : i32, !fir.ref<i32>
+!    omp.parallel private(@var1.privatizer_0 %1#0, @var2.privatizer_0 %3#0 : !fir.ref<i32>, !fir.ref<i32>) {
+!    ^bb0(%arg0: !fir.ref<i32>, %arg1: !fir.ref<i32>):
+!      %4:2 = hlfir.declare %arg0 {uniq_name = "_QFdelayed_privatizationEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!      %5:2 = hlfir.declare %arg1 {uniq_name = "_QFdelayed_privatizationEvar2"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!      %6 = fir.load %4#0 : !fir.ref<i32>
+!      %7 = fir.load %5#0 : !fir.ref<i32>
+!      %8 = arith.addi %6, %7 : i32
+!      %c2_i32 = arith.constant 2 : i32
+!      %9 = arith.addi %8, %c2_i32 : i32
+!      hlfir.assign %9 to %4#0 : i32, !fir.ref<i32>
+!      omp.terminator
+!    }
+!    return
+!  }
+!  "omp.private"() <{function_type = (!fir.ref<i32>) -> !fir.ref<i32>, sym_name = "var1.privatizer_0"}> ({
+!  ^bb0(%arg0: !fir.ref<i32>):
+!    %0 = fir.alloca i32 {bindc_name = "var1", pinned, uniq_name = "_QFdelayed_privatizationEvar1"}
+!    %1:2 = hlfir.declare %0 {uniq_name = "_QFdelayed_privatizationEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!    %2 = fir.load %arg0 : !fir.ref<i32>
+!    hlfir.assign %2 to %1#0 temporary_lhs : i32, !fir.ref<i32>
+!    omp.yield(%1#0 : !fir.ref<i32>)
+!  }) : () -> ()
+!  "omp.private"() <{function_type = (!fir.ref<i32>) -> !fir.ref<i32>, sym_name = "var2.privatizer_0"}> ({
+!  ^bb0(%arg0: !fir.ref<i32>):
+!    %0 = fir.alloca i32 {bindc_name = "var2", pinned, uniq_name = "_QFdelayed_privatizationEvar2"}
+!    %1:2 = hlfir.declare %0 {uniq_name = "_QFdelayed_privatizationEvar2"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!    %2 = fir.load %arg0 : !fir.ref<i32>
+!    hlfir.assign %2 to %1#0 temporary_lhs : i32, !fir.ref<i32>
+!    omp.yield(%1#0 : !fir.ref<i32>)
+!  }) : () -> ()
+!}
+!
+!
+! ### After lowring `hlfir` to `fir`, conversion to LLVM + OMP -> LLVM IR produces the exact same result as for
+! `delayed_privatization.f90`.