[CIR][OpenMP] Initial commit for OpenMP support in CIR (llvm#382)

This patch introduces initial support for:
```
pragma omp parallel
```

This patch doesn't add support for any of the `parallel` clauses,
including variable privatization; thus, all variables are handled as
shared.

This PR fixes issue llvm#285.

clang/lib/CIR/CodeGen/CIRGenDecl.cpp

@@ -14,6 +14,7 @@
 #include "CIRGenBuilder.h"
 #include "CIRGenCstEmitter.h"
 #include "CIRGenFunction.h"
+#include "CIRGenOpenMPRuntime.h"
 #include "EHScopeStack.h"
 #include "UnimplementedFeatureGuarding.h"
 #include "mlir/IR/Attributes.h"
@@ -37,13 +38,8 @@ CIRGenFunction::buildAutoVarAlloca(const VarDecl &D) {
   // TODO: (|| Ty.getAddressSpace() == LangAS::opencl_private &&
   //        getLangOpts().OpenCL))
   assert(!UnimplementedFeature::openCL());
-  assert(!UnimplementedFeature::openMP());
   assert(Ty.getAddressSpace() == LangAS::Default);
   assert(!Ty->isVariablyModifiedType() && "not implemented");
-  assert(!getContext()
-              .getLangOpts()
-              .OpenMP && // !CGF.getLangOpts().OpenMPIRBuilder
-         "not implemented");
   assert(!D.hasAttr<AnnotateAttr>() && "not implemented");
 
   auto loc = getLoc(D.getSourceRange());
@@ -59,7 +55,9 @@ CIRGenFunction::buildAutoVarAlloca(const VarDecl &D) {
 
   Address address = Address::invalid();
   Address allocaAddr = Address::invalid();
-  Address openMPLocalAddr = Address::invalid();
+  Address openMPLocalAddr =
+      getCIRGenModule().getOpenMPRuntime().getAddressOfLocalVariable(*this, &D);
+  assert(!getLangOpts().OpenMPIsTargetDevice && "NYI");
   if (getLangOpts().OpenMP && openMPLocalAddr.isValid()) {
     llvm_unreachable("NYI");
   } else if (Ty->isConstantSizeType()) {

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -15,6 +15,7 @@
 #include "CIRGenCstEmitter.h"
 #include "CIRGenFunction.h"
 #include "CIRGenModule.h"
+#include "CIRGenOpenMPRuntime.h"
 #include "CIRGenValue.h"
 #include "UnimplementedFeatureGuarding.h"
 
@@ -759,8 +760,11 @@ LValue CIRGenFunction::buildDeclRefLValue(const DeclRefExpr *E) {
       if (auto *FD = LambdaCaptureFields.lookup(VD))
         return buildCapturedFieldLValue(*this, FD, CXXABIThisValue);
       assert(!UnimplementedFeature::CGCapturedStmtInfo() && "NYI");
-      llvm_unreachable("NYI");
+      // TODO[OpenMP]: Find the appropiate captured variable value and return
+      // it.
+      // TODO[OpenMP]: Set non-temporal information in the captured LVal.
       // LLVM codegen:
+      assert(!UnimplementedFeature::openMP());
       // Address addr = GetAddrOfBlockDecl(VD);
       // return MakeAddrLValue(addr, T, AlignmentSource::Decl);
     }
@@ -910,9 +914,9 @@ LValue CIRGenFunction::buildBinaryOperatorLValue(const BinaryOperator *E) {
     } else {
       buildStoreThroughLValue(RV, LV);
     }
-
-    assert(!getContext().getLangOpts().OpenMP &&
-           "last priv cond not implemented");
+    if (getLangOpts().OpenMP)
+      CGM.getOpenMPRuntime().checkAndEmitLastprivateConditional(*this,
+                                                                E->getLHS());
     return LV;
   }
 

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -14,6 +14,7 @@
 #include "CIRDataLayout.h"
 #include "CIRGenFunction.h"
 #include "CIRGenModule.h"
+#include "CIRGenOpenMPRuntime.h"
 #include "UnimplementedFeatureGuarding.h"
 
 #include "clang/AST/StmtVisitor.h"
@@ -1805,7 +1806,9 @@ LValue ScalarExprEmitter::buildCompoundAssignLValue(
   else
     CGF.buildStoreThroughLValue(RValue::get(Result), LHSLV);
 
-  assert(!CGF.getLangOpts().OpenMP && "Not implemented");
+  if (CGF.getLangOpts().OpenMP)
+    CGF.CGM.getOpenMPRuntime().checkAndEmitLastprivateConditional(CGF,
+                                                                  E->getLHS());
   return LHSLV;
 }
 

clang/lib/CIR/CodeGen/CIRGenFunction.cpp

@@ -13,6 +13,7 @@
 #include "CIRGenFunction.h"
 #include "CIRGenCXXABI.h"
 #include "CIRGenModule.h"
+#include "CIRGenOpenMPRuntime.h"
 #include "UnimplementedFeatureGuarding.h"
 
 #include "clang/AST/ASTLambda.h"
@@ -974,7 +975,7 @@ void CIRGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
   // TODO: prologuecleanupdepth
 
   if (getLangOpts().OpenMP && CurCodeDecl)
-    llvm_unreachable("NYI");
+    CGM.getOpenMPRuntime().emitFunctionProlog(*this, CurCodeDecl);
 
   // TODO: buildFunctionProlog
 

clang/lib/CIR/CodeGen/CIRGenFunction.h

@@ -928,6 +928,9 @@ class CIRGenFunction : public CIRGenTypeCache {
   mlir::LogicalResult buildBreakStmt(const clang::BreakStmt &S);
   mlir::LogicalResult buildContinueStmt(const clang::ContinueStmt &S);
 
+  // OpenMP gen functions:
+  mlir::LogicalResult buildOMPParallelDirective(const OMPParallelDirective &S);
+
   LValue buildOpaqueValueLValue(const OpaqueValueExpr *e);
 
   /// Emit code to compute a designator that specifies the location

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -15,6 +15,7 @@
 #include "CIRGenCXXABI.h"
 #include "CIRGenCstEmitter.h"
 #include "CIRGenFunction.h"
+#include "CIRGenOpenMPRuntime.h"
 #include "CIRGenTypes.h"
 #include "CIRGenValue.h"
 #include "TargetInfo.h"
@@ -103,7 +104,7 @@ CIRGenModule::CIRGenModule(mlir::MLIRContext &context,
       codeGenOpts(CGO),
       theModule{mlir::ModuleOp::create(builder.getUnknownLoc())}, Diags(Diags),
       target(astCtx.getTargetInfo()), ABI(createCXXABI(*this)), genTypes{*this},
-      VTables{*this} {
+      VTables{*this}, openMPRuntime(new CIRGenOpenMPRuntime(*this)) {
 
   // Initialize CIR signed integer types cache.
   SInt8Ty =
@@ -316,7 +317,18 @@ bool CIRGenModule::MustBeEmitted(const ValueDecl *Global) {
 }
 
 bool CIRGenModule::MayBeEmittedEagerly(const ValueDecl *Global) {
-  assert(!langOpts.OpenMP && "NYI");
+  // In OpenMP 5.0 variables and function may be marked as
+  // device_type(host/nohost) and we should not emit them eagerly unless we sure
+  // that they must be emitted on the host/device. To be sure we need to have
+  // seen a declare target with an explicit mentioning of the function, we know
+  // we have if the level of the declare target attribute is -1. Note that we
+  // check somewhere else if we should emit this at all.
+  if (langOpts.OpenMP >= 50 && !langOpts.OpenMPSimd) {
+    std::optional<OMPDeclareTargetDeclAttr *> ActiveAttr =
+        OMPDeclareTargetDeclAttr::getActiveAttr(Global);
+    if (!ActiveAttr || (*ActiveAttr)->getLevel() != (unsigned)-1)
+      return false;
+  }
 
   const auto *FD = dyn_cast<FunctionDecl>(Global);
   if (FD) {
@@ -336,6 +348,15 @@ bool CIRGenModule::MayBeEmittedEagerly(const ValueDecl *Global) {
                ASTContext::InlineVariableDefinitionKind::WeakUnknown &&
            "not implemented");
 
+  // If OpenMP is enabled and threadprivates must be generated like TLS, delay
+  // codegen for global variables, because they may be marked as threadprivate.
+  if (langOpts.OpenMP && langOpts.OpenMPUseTLS &&
+      getASTContext().getTargetInfo().isTLSSupported() &&
+      isa<VarDecl>(Global) &&
+      !Global->getType().isConstantStorage(getASTContext(), false, false) &&
+      !OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(Global))
+    return false;
+
   assert((FD || VD) &&
          "Only FunctionDecl and VarDecl should hit this path so far.");
   return true;
@@ -347,7 +368,22 @@ void CIRGenModule::buildGlobal(GlobalDecl GD) {
   assert(!Global->hasAttr<IFuncAttr>() && "NYI");
   assert(!Global->hasAttr<CPUDispatchAttr>() && "NYI");
   assert(!langOpts.CUDA && "NYI");
-  assert(!langOpts.OpenMP && "NYI");
+
+  if (langOpts.OpenMP) {
+    // If this is OpenMP, check if it is legal to emit this global normally.
+    if (openMPRuntime && openMPRuntime->emitTargetGlobal(GD)) {
+      assert(!UnimplementedFeature::openMPRuntime());
+      return;
+    }
+    if (auto *DRD = dyn_cast<OMPDeclareReductionDecl>(Global)) {
+      assert(!UnimplementedFeature::openMP());
+      return;
+    }
+    if (auto *DMD = dyn_cast<OMPDeclareMapperDecl>(Global)) {
+      assert(!UnimplementedFeature::openMP());
+      return;
+    }
+  }
 
   // Ignore declarations, they will be emitted on their first use.
   if (const auto *FD = dyn_cast<FunctionDecl>(Global)) {
@@ -371,7 +407,13 @@ void CIRGenModule::buildGlobal(GlobalDecl GD) {
     assert(VD->isFileVarDecl() && "Cannot emit local var decl as global.");
     if (VD->isThisDeclarationADefinition() != VarDecl::Definition &&
         !astCtx.isMSStaticDataMemberInlineDefinition(VD)) {
-      assert(!getLangOpts().OpenMP && "not implemented");
+      if (langOpts.OpenMP) {
+        // Emit declaration of the must-be-emitted declare target variable.
+        if (std::optional<OMPDeclareTargetDeclAttr::MapTypeTy> Res =
+                OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(VD)) {
+          assert(0 && "OMPDeclareTargetDeclAttr NYI");
+        }
+      }
       // If this declaration may have caused an inline variable definition
       // to change linkage, make sure that it's emitted.
       // TODO(cir): probably use GetAddrOfGlobalVar(VD) below?
@@ -576,8 +618,8 @@ CIRGenModule::getOrCreateCIRGlobal(StringRef MangledName, mlir::Type Ty,
         !D->hasAttr<clang::DLLExportAttr>())
       assert(!UnimplementedFeature::setDLLStorageClass() && "NYI");
 
-    if (getLangOpts().OpenMP && !getLangOpts().OpenMPSimd && D)
-      assert(0 && "not implemented");
+    if (langOpts.OpenMP && !langOpts.OpenMPSimd && D)
+      getOpenMPRuntime().registerTargetGlobalVariable(D, Entry);
 
     // TODO(cir): check TargetAS matches Entry address space
     if (Entry.getSymType() == Ty &&
@@ -647,10 +689,9 @@ CIRGenModule::getOrCreateCIRGlobal(StringRef MangledName, mlir::Type Ty,
   }
 
   // Handle things which are present even on external declarations.
-  auto &LangOpts = getLangOpts();
   if (D) {
-    if (LangOpts.OpenMP && !LangOpts.OpenMPSimd)
-      assert(0 && "not implemented");
+    if (langOpts.OpenMP && !langOpts.OpenMPSimd && D)
+      getOpenMPRuntime().registerTargetGlobalVariable(D, Entry);
 
     // FIXME: This code is overly simple and should be merged with other global
     // handling.
@@ -2052,8 +2093,11 @@ mlir::cir::FuncOp CIRGenModule::GetOrCreateCIRFunction(
   // Any attempts to use a MultiVersion function should result in retrieving the
   // iFunc instead. Name mangling will handle the rest of the changes.
   if (const auto *FD = cast_or_null<FunctionDecl>(D)) {
-    if (getLangOpts().OpenMP)
-      llvm_unreachable("open MP NYI");
+    // For the device mark the function as one that should be emitted.
+    if (getLangOpts().OpenMPIsTargetDevice && FD->isDefined() && !DontDefer &&
+        !IsForDefinition) {
+      assert(0 && "OpenMP target functions NYI");
+    }
     if (FD->isMultiVersion())
       llvm_unreachable("NYI");
   }
@@ -2291,9 +2335,9 @@ void CIRGenModule::buildGlobalDecl(clang::GlobalDecl &D) {
   }
 
   // If this is OpenMP, check if it is legal to emit this global normally.
-  if (getLangOpts().OpenMP) {
-    llvm_unreachable("NYI");
-  }
+  if (getLangOpts().OpenMP && openMPRuntime &&
+      openMPRuntime->emitTargetGlobal(D))
+    return;
 
   // Otherwise, emit the definition and move on to the next one.
   buildGlobalDefinition(D, Op);
@@ -2302,7 +2346,7 @@ void CIRGenModule::buildGlobalDecl(clang::GlobalDecl &D) {
 void CIRGenModule::buildDeferred(unsigned recursionLimit) {
   // Emit deferred declare target declarations
   if (getLangOpts().OpenMP && !getLangOpts().OpenMPSimd)
-    llvm_unreachable("NYI");
+    getOpenMPRuntime().emitDeferredTargetDecls();
 
   // Emit code for any potentially referenced deferred decls. Since a previously
   // unused static decl may become used during the generation of code for a

clang/lib/CIR/CodeGen/CIRGenModule.h

@@ -46,6 +46,7 @@ namespace cir {
 class CIRGenFunction;
 class CIRGenCXXABI;
 class TargetCIRGenInfo;
+class CIRGenOpenMPRuntime;
 
 enum ForDefinition_t : bool { NotForDefinition = false, ForDefinition = true };
 
@@ -100,6 +101,9 @@ class CIRGenModule : public CIRGenTypeCache {
   /// Holds information about C++ vtables.
   CIRGenVTables VTables;
 
+  /// Holds the OpenMP runtime
+  std::unique_ptr<CIRGenOpenMPRuntime> openMPRuntime;
+
   /// Per-function codegen information. Updated everytime buildCIR is called
   /// for FunctionDecls's.
   CIRGenFunction *CurCGF = nullptr;
@@ -626,6 +630,12 @@ class CIRGenModule : public CIRGenTypeCache {
   /// Print out an error that codegen doesn't support the specified decl yet.
   void ErrorUnsupported(const Decl *D, const char *Type);
 
+  /// Return a reference to the configured OpenMP runtime.
+  CIRGenOpenMPRuntime &getOpenMPRuntime() {
+    assert(openMPRuntime != nullptr);
+    return *openMPRuntime;
+  }
+
 private:
   // An ordered map of canonical GlobalDecls to their mangled names.
   llvm::MapVector<clang::GlobalDecl, llvm::StringRef> MangledDeclNames;

clang/lib/CIR/CodeGen/CIRGenOpenMPRuntime.cpp

@@ -0,0 +1,54 @@
+//===--- CIRGenStmtOpenMP.cpp - Interface to OpenMP Runtimes --------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This provides a class for OpenMP runtime MLIR code generation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CIRGenOpenMPRuntime.h"
+#include "CIRGenFunction.h"
+#include "CIRGenModule.h"
+
+using namespace cir;
+using namespace clang;
+
+CIRGenOpenMPRuntime::CIRGenOpenMPRuntime(CIRGenModule &CGM) : CGM(CGM) {}
+
+Address CIRGenOpenMPRuntime::getAddressOfLocalVariable(CIRGenFunction &CGF,
+                                                       const VarDecl *VD) {
+  assert(!UnimplementedFeature::openMPRuntime());
+  return Address::invalid();
+}
+
+void CIRGenOpenMPRuntime::checkAndEmitLastprivateConditional(
+    CIRGenFunction &CGF, const Expr *LHS) {
+  assert(!UnimplementedFeature::openMPRuntime());
+  return;
+}
+
+void CIRGenOpenMPRuntime::registerTargetGlobalVariable(
+    const clang::VarDecl *VD, mlir::cir::GlobalOp globalOp) {
+  assert(!UnimplementedFeature::openMPRuntime());
+  return;
+}
+
+void CIRGenOpenMPRuntime::emitDeferredTargetDecls() const {
+  assert(!UnimplementedFeature::openMPRuntime());
+  return;
+}
+
+void CIRGenOpenMPRuntime::emitFunctionProlog(CIRGenFunction &CGF,
+                                             const clang::Decl *D) {
+  assert(!UnimplementedFeature::openMPRuntime());
+  return;
+}
+
+bool CIRGenOpenMPRuntime::emitTargetGlobal(clang::GlobalDecl &GD) {
+  assert(!UnimplementedFeature::openMPRuntime());
+  return false;
+}