[flang] Implement !DIR$ [NO]INLINE and FORCEINLINE directives

flang/docs/Directives.md

@@ -53,6 +53,14 @@ A list of non-standard directives supported by Flang
 * `!dir$ novector` disabling vectorization on the following loop.
 * `!dir$ nounroll` disabling unrolling on the following loop.
 * `!dir$ nounroll_and_jam` disabling unrolling and jamming on the following loop.
+* `!dir$ inline` tells the compiler to attempt to inline routines if 
+  this directive is specified before a call statement or for all call function statements
+  within a DO LOOP. This directive can be improved later to support other place(s) for  
+  inlining function calls.
+* `!dir$ forceinline` works in the same way as the `inline` directive, but it force 
+   inlining by the compiler on a function call statement.
+* `!dir$ noinline` works in the same way as the `inline` directive, but prevents 
+  any attempt of inlining by the compiler on a function call statement.
 
 # Directive Details
 

flang/include/flang/Evaluate/call.h

@@ -254,6 +254,13 @@ class ProcedureRef {
   bool IsElemental() const { return proc_.IsElemental(); }
   bool hasAlternateReturns() const { return hasAlternateReturns_; }
 
+  bool hasNoInline() const { return noInline_; }
+  void set_noInline(bool ni) { noInline_ = ni; }
+  bool hasAlwaysInline() const { return alwaysInline_; }
+  void set_alwaysInline(bool ai) { alwaysInline_ = ai; }
+  bool hasInlineHint() const { return inlineHint_; }
+  void set_inlineHint(bool ih) { inlineHint_ = ih; }
+
   Expr<SomeType> *UnwrapArgExpr(int n) {
     if (static_cast<std::size_t>(n) < arguments_.size() && arguments_[n]) {
       return arguments_[n]->UnwrapExpr();
@@ -277,6 +284,9 @@ class ProcedureRef {
   ActualArguments arguments_;
   Chevrons chevrons_;
   bool hasAlternateReturns_;
+  bool noInline_{false};
+  bool alwaysInline_{false};
+  bool inlineHint_{false};
 };
 
 template <typename A> class FunctionRef : public ProcedureRef {

flang/include/flang/Optimizer/Dialect/FIRAttr.td

@@ -200,4 +200,24 @@ def fir_OpenMPSafeTempArrayCopyAttr : fir_Attr<"OpenMPSafeTempArrayCopy"> {
   }];
 }
 
+/// Fortran inline attribute
+def FIRinlineNone : I32BitEnumAttrCaseNone<"none">;
+def FIRinlineNo : I32BitEnumAttrCaseBit<"no_inline", 0>;
+def FIRinlineAlways : I32BitEnumAttrCaseBit<"always_inline", 1>;
+def FIRinlineHint : I32BitEnumAttrCaseBit<"inline_hint", 2>;
+
+def fir_FortranInlineEnum
+    : I32BitEnumAttr<"FortranInlineEnum", "Fortran inline attributes",
+                     [FIRinlineNone, FIRinlineNo, FIRinlineAlways,
+                      FIRinlineHint]> {
+  let separator = ", ";
+  let cppNamespace = "::fir";
+  let genSpecializedAttr = 0;
+  let printBitEnumPrimaryGroups = 1;
+}
+
+def fir_FortranInlineAttr
+    : EnumAttr<FIROpsDialect, fir_FortranInlineEnum, "inline_attrs"> {
+  let assemblyFormat = "`<` $value `>`";
+}
 #endif // FIR_DIALECT_FIR_ATTRS

flang/include/flang/Optimizer/Dialect/FIROps.td

@@ -2494,6 +2494,7 @@ def fir_CallOp : fir_Op<"call",
     OptionalAttr<DictArrayAttr>:$arg_attrs,
     OptionalAttr<DictArrayAttr>:$res_attrs,
     OptionalAttr<fir_FortranProcedureFlagsAttr>:$procedure_attrs,
+    OptionalAttr<fir_FortranInlineAttr>:$inline_attr,
     DefaultValuedAttr<Arith_FastMathAttr,
                       "::mlir::arith::FastMathFlags::none">:$fastmath
   );

flang/include/flang/Parser/dump-parse-tree.h

@@ -204,8 +204,11 @@ class ParseTreeDumper {
   NODE(parser, CompilerDirective)
   NODE(CompilerDirective, AssumeAligned)
   NODE(CompilerDirective, IgnoreTKR)
+  NODE(CompilerDirective, Inline)
+  NODE(CompilerDirective, ForceInline)
   NODE(CompilerDirective, LoopCount)
   NODE(CompilerDirective, NameValue)
+  NODE(CompilerDirective, NoInline)
   NODE(CompilerDirective, Unrecognized)
   NODE(CompilerDirective, VectorAlways)
   NODE(CompilerDirective, Unroll)

flang/include/flang/Parser/parse-tree.h

@@ -3354,6 +3354,9 @@ struct StmtFunctionStmt {
 // !DIR$ NOVECTOR
 // !DIR$ NOUNROLL
 // !DIR$ NOUNROLL_AND_JAM
+// !DIR$ FORCEINLINE
+// !DIR$ INLINE
+// !DIR$ NOINLINE
 // !DIR$ <anything else>
 struct CompilerDirective {
   UNION_CLASS_BOILERPLATE(CompilerDirective);
@@ -3382,11 +3385,14 @@ struct CompilerDirective {
   EMPTY_CLASS(NoVector);
   EMPTY_CLASS(NoUnroll);
   EMPTY_CLASS(NoUnrollAndJam);
+  EMPTY_CLASS(ForceInline);
+  EMPTY_CLASS(Inline);
+  EMPTY_CLASS(NoInline);
   EMPTY_CLASS(Unrecognized);
   CharBlock source;
   std::variant<std::list<IgnoreTKR>, LoopCount, std::list<AssumeAligned>,
       VectorAlways, std::list<NameValue>, Unroll, UnrollAndJam, Unrecognized,
-      NoVector, NoUnroll, NoUnrollAndJam>
+      NoVector, NoUnroll, NoUnrollAndJam, ForceInline, Inline, NoInline>
       u;
 };
 

flang/lib/Lower/Bridge.cpp

@@ -1828,6 +1828,26 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     setCurrentPosition(stmt.source);
     assert(stmt.typedCall && "Call was not analyzed");
     mlir::Value res{};
+
+    // Set 'no_inline', 'inline_hint' or 'always_inline' to true on the
+    // ProcedureRef. The NoInline and AlwaysInline attribute will be set in
+    // genProcedureRef later.
+    for (const auto *dir : eval.dirs) {
+      Fortran::common::visit(
+          Fortran::common::visitors{
+              [&](const Fortran::parser::CompilerDirective::ForceInline &) {
+                stmt.typedCall->set_alwaysInline(true);
+              },
+              [&](const Fortran::parser::CompilerDirective::Inline &) {
+                stmt.typedCall->set_inlineHint(true);
+              },
+              [&](const Fortran::parser::CompilerDirective::NoInline &) {
+                stmt.typedCall->set_noInline(true);
+              },
+              [&](const auto &) {}},
+          dir->u);
+    }
+
     if (lowerToHighLevelFIR()) {
       std::optional<mlir::Type> resultType;
       if (stmt.typedCall->hasAlternateReturns())
@@ -2053,6 +2073,50 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     // so no clean-up needs to be generated for these entities.
   }
 
+  void attachInlineAttributes(
+      mlir::Operation &op,
+      const llvm::ArrayRef<const Fortran::parser::CompilerDirective *> &dirs) {
+    if (dirs.empty())
+      return;
+
+    for (mlir::Value operand : op.getOperands()) {
+      if (operand.getDefiningOp())
+        attachInlineAttributes(*operand.getDefiningOp(), dirs);
+    }
+
+    if (fir::CallOp callOp = mlir::dyn_cast<fir::CallOp>(op)) {
+      for (const auto *dir : dirs) {
+        Fortran::common::visit(
+            Fortran::common::visitors{
+                [&](const Fortran::parser::CompilerDirective::NoInline &) {
+                  callOp.setInlineAttr(fir::FortranInlineEnum::no_inline);
+                },
+                [&](const Fortran::parser::CompilerDirective::Inline &) {
+                  callOp.setInlineAttr(fir::FortranInlineEnum::inline_hint);
+                },
+                [&](const Fortran::parser::CompilerDirective::ForceInline &) {
+                  callOp.setInlineAttr(fir::FortranInlineEnum::always_inline);
+                },
+                [&](const auto &) {}},
+            dir->u);
+      }
+    }
+  }
+
+  void attachAttributesToDoLoopOperations(
+      fir::DoLoopOp &doLoop,
+      llvm::SmallVectorImpl<const Fortran::parser::CompilerDirective *> &dirs) {
+    if (!doLoop.getOperation() || dirs.empty())
+      return;
+
+    for (mlir::Block &block : doLoop.getRegion()) {
+      for (mlir::Operation &op : block.getOperations()) {
+        if (!dirs.empty())
+          attachInlineAttributes(op, dirs);
+      }
+    }
+  }
+
   /// Generate FIR for a DO construct. There are six variants:
   ///  - unstructured infinite and while loops
   ///  - structured and unstructured increment loops
@@ -2162,6 +2226,10 @@ class FirConverter : public Fortran::lower::AbstractConverter {
 
     // This call may generate a branch in some contexts.
     genFIR(endDoEval, unstructuredContext);
+
+    // Add attribute(s) on operations in fir::DoLoopOp if necessary
+    for (IncrementLoopInfo &info : incrementLoopNestInfo)
+      attachAttributesToDoLoopOperations(info.doLoop, doStmtEval.dirs);
   }
 
   /// Generate FIR to evaluate loop control values (lower, upper and step).
@@ -2935,6 +3003,26 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       e->dirs.push_back(&dir);
   }
 
+  void
+  attachInliningDirectiveToStmt(const Fortran::parser::CompilerDirective &dir,
+                                Fortran::lower::pft::Evaluation *e) {
+    while (e->isDirective())
+      e = e->lexicalSuccessor;
+
+    // If the successor is a statement or a do loop, the compiler
+    // will perform inlining.
+    if (e->isA<Fortran::parser::CallStmt>() ||
+        e->isA<Fortran::parser::NonLabelDoStmt>() ||
+        e->isA<Fortran::parser::AssignmentStmt>()) {
+      e->dirs.push_back(&dir);
+    } else {
+      mlir::Location loc = toLocation();
+      mlir::emitWarning(loc,
+                        "Inlining directive not in front of loops, function"
+                        "call or assignment.\n");
+    }
+  }
+
   void genFIR(const Fortran::parser::CompilerDirective &dir) {
     Fortran::lower::pft::Evaluation &eval = getEval();
 
@@ -2958,6 +3046,15 @@ class FirConverter : public Fortran::lower::AbstractConverter {
             [&](const Fortran::parser::CompilerDirective::NoUnrollAndJam &) {
               attachDirectiveToLoop(dir, &eval);
             },
+            [&](const Fortran::parser::CompilerDirective::ForceInline &) {
+              attachInliningDirectiveToStmt(dir, &eval);
+            },
+            [&](const Fortran::parser::CompilerDirective::Inline &) {
+              attachInliningDirectiveToStmt(dir, &eval);
+            },
+            [&](const Fortran::parser::CompilerDirective::NoInline &) {
+              attachInliningDirectiveToStmt(dir, &eval);
+            },
             [&](const auto &) {}},
         dir.u);
   }
@@ -4761,7 +4858,9 @@ class FirConverter : public Fortran::lower::AbstractConverter {
 
   void genDataAssignment(
       const Fortran::evaluate::Assignment &assign,
-      const Fortran::evaluate::ProcedureRef *userDefinedAssignment) {
+      const Fortran::evaluate::ProcedureRef *userDefinedAssignment,
+      const llvm::ArrayRef<const Fortran::parser::CompilerDirective *> &dirs =
+          {}) {
     mlir::Location loc = getCurrentLocation();
     fir::FirOpBuilder &builder = getFirOpBuilder();
 
@@ -4834,12 +4933,22 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       Fortran::lower::StatementContext localStmtCtx;
       hlfir::Entity rhs = evaluateRhs(localStmtCtx);
       hlfir::Entity lhs = evaluateLhs(localStmtCtx);
-      if (isCUDATransfer && !hasCUDAImplicitTransfer)
+      if (isCUDATransfer && !hasCUDAImplicitTransfer) {
         genCUDADataTransfer(builder, loc, assign, lhs, rhs);
-      else
+      } else {
+        // If RHS or LHS have a CallOp in their expression, this operation will
+        // have the 'no_inline' or 'always_inline' attribute if there is a
+        // directive just before the assignement.
+        if (!dirs.empty()) {
+          if (rhs.getDefiningOp())
+            attachInlineAttributes(*rhs.getDefiningOp(), dirs);
+          if (lhs.getDefiningOp())
+            attachInlineAttributes(*lhs.getDefiningOp(), dirs);
+        }
         builder.create<hlfir::AssignOp>(loc, rhs, lhs,
                                         isWholeAllocatableAssignment,
                                         keepLhsLengthInAllocatableAssignment);
+      }
       if (hasCUDAImplicitTransfer && !isInDeviceContext) {
         localSymbols.popScope();
         for (mlir::Value temp : implicitTemps)
@@ -4907,16 +5016,21 @@ class FirConverter : public Fortran::lower::AbstractConverter {
   }
 
   /// Shared for both assignments and pointer assignments.
-  void genAssignment(const Fortran::evaluate::Assignment &assign) {
+  void
+  genAssignment(const Fortran::evaluate::Assignment &assign,
+                const llvm::ArrayRef<const Fortran::parser::CompilerDirective *>
+                    &dirs = {}) {
     mlir::Location loc = toLocation();
     if (lowerToHighLevelFIR()) {
       Fortran::common::visit(
           Fortran::common::visitors{
               [&](const Fortran::evaluate::Assignment::Intrinsic &) {
-                genDataAssignment(assign, /*userDefinedAssignment=*/nullptr);
+                genDataAssignment(assign, /*userDefinedAssignment=*/nullptr,
+                                  dirs);
               },
               [&](const Fortran::evaluate::ProcedureRef &procRef) {
-                genDataAssignment(assign, /*userDefinedAssignment=*/&procRef);
+                genDataAssignment(assign, /*userDefinedAssignment=*/&procRef,
+                                  dirs);
               },
               [&](const Fortran::evaluate::Assignment::BoundsSpec &lbExprs) {
                 if (isInsideHlfirForallOrWhere())
@@ -5321,7 +5435,8 @@ class FirConverter : public Fortran::lower::AbstractConverter {
   }
 
   void genFIR(const Fortran::parser::AssignmentStmt &stmt) {
-    genAssignment(*stmt.typedAssignment->v);
+    Fortran::lower::pft::Evaluation &eval = getEval();
+    genAssignment(*stmt.typedAssignment->v, eval.dirs);
   }
 
   void genFIR(const Fortran::parser::SyncAllStmt &stmt) {

flang/lib/Lower/ConvertCall.cpp

@@ -645,9 +645,20 @@ Fortran::lower::genCallOpAndResult(
       callResult = dispatch.getResult(0);
   } else {
     // Standard procedure call with fir.call.
+    fir::FortranInlineEnumAttr inlineAttr;
+
+    if (caller.getCallDescription().hasNoInline())
+      inlineAttr = fir::FortranInlineEnumAttr::get(
+          builder.getContext(), fir::FortranInlineEnum::no_inline);
+    else if (caller.getCallDescription().hasInlineHint())
+      inlineAttr = fir::FortranInlineEnumAttr::get(
+          builder.getContext(), fir::FortranInlineEnum::inline_hint);
+    else if (caller.getCallDescription().hasAlwaysInline())
+      inlineAttr = fir::FortranInlineEnumAttr::get(
+          builder.getContext(), fir::FortranInlineEnum::always_inline);
     auto call = builder.create<fir::CallOp>(
         loc, funcType.getResults(), funcSymbolAttr, operands,
-        /*arg_attrs=*/nullptr, /*res_attrs=*/nullptr, procAttrs);
+        /*arg_attrs=*/nullptr, /*res_attrs=*/nullptr, procAttrs, inlineAttr);
 
     callNumResults = call.getNumResults();
     if (callNumResults != 0)

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -634,6 +634,18 @@ struct CallOpConversion : public fir::FIROpConversion<fir::CallOp> {
     if (mlir::ArrayAttr resAttrs = call.getResAttrsAttr())
       llvmCall.setResAttrsAttr(resAttrs);
 
+    if (auto inlineAttr = call.getInlineAttrAttr()) {
+      llvmCall->removeAttr("inline_attr");
+      if (inlineAttr.getValue() == fir::FortranInlineEnum::no_inline) {
+        llvmCall.setNoInlineAttr(rewriter.getUnitAttr());
+      } else if (inlineAttr.getValue() == fir::FortranInlineEnum::inline_hint) {
+        llvmCall.setInlineHintAttr(rewriter.getUnitAttr());
+      } else if (inlineAttr.getValue() ==
+                 fir::FortranInlineEnum::always_inline) {
+        llvmCall.setAlwaysInlineAttr(rewriter.getUnitAttr());
+      }
+    }
+
     if (memAttr)
       llvmCall.setMemoryEffectsAttr(
           mlir::cast<mlir::LLVM::MemoryEffectsAttr>(memAttr));

flang/lib/Optimizer/Transforms/PolymorphicOpConversion.cpp

@@ -207,7 +207,8 @@ struct DispatchOpConv : public OpConversionPattern<fir::DispatchOp> {
     args.append(dispatch.getArgs().begin(), dispatch.getArgs().end());
     rewriter.replaceOpWithNewOp<fir::CallOp>(
         dispatch, resTypes, nullptr, args, dispatch.getArgAttrsAttr(),
-        dispatch.getResAttrsAttr(), dispatch.getProcedureAttrsAttr());
+        dispatch.getResAttrsAttr(), dispatch.getProcedureAttrsAttr(),
+        /*inline_attr*/ fir::FortranInlineEnumAttr{});
     return mlir::success();
   }
 

flang/lib/Parser/Fortran-parsers.cpp

@@ -1314,6 +1314,11 @@ constexpr auto novector{"NOVECTOR" >> construct<CompilerDirective::NoVector>()};
 constexpr auto nounroll{"NOUNROLL" >> construct<CompilerDirective::NoUnroll>()};
 constexpr auto nounrollAndJam{
     "NOUNROLL_AND_JAM" >> construct<CompilerDirective::NoUnrollAndJam>()};
+constexpr auto forceinlineDir{
+    "FORCEINLINE" >> construct<CompilerDirective::ForceInline>()};
+constexpr auto noinlineDir{
+    "NOINLINE" >> construct<CompilerDirective::NoInline>()};
+constexpr auto inlineDir{"INLINE" >> construct<CompilerDirective::Inline>()};
 TYPE_PARSER(beginDirective >> "DIR$ "_tok >>
     sourced((construct<CompilerDirective>(ignore_tkr) ||
                 construct<CompilerDirective>(loopCount) ||
@@ -1324,6 +1329,9 @@ TYPE_PARSER(beginDirective >> "DIR$ "_tok >>
                 construct<CompilerDirective>(novector) ||
                 construct<CompilerDirective>(nounrollAndJam) ||
                 construct<CompilerDirective>(nounroll) ||
+                construct<CompilerDirective>(noinlineDir) ||
+                construct<CompilerDirective>(forceinlineDir) ||
+                construct<CompilerDirective>(inlineDir) ||
                 construct<CompilerDirective>(
                     many(construct<CompilerDirective::NameValue>(
                         name, maybe(("="_tok || ":"_tok) >> digitString64))))) /

flang/lib/Parser/unparse.cpp

@@ -1864,6 +1864,13 @@ class UnparseVisitor {
             [&](const CompilerDirective::NoUnrollAndJam &) {
               Word("!DIR$ NOUNROLL_AND_JAM");
             },
+            [&](const CompilerDirective::ForceInline &) {
+              Word("!DIR$ FORCEINLINE");
+            },
+            [&](const CompilerDirective::Inline &) { Word("!DIR$ INLINE"); },
+            [&](const CompilerDirective::NoInline &) {
+              Word("!DIR$ NOINLINE");
+            },
             [&](const CompilerDirective::Unrecognized &) {
               Word("!DIR$ ");
               Word(x.source.ToString());