[OPENMP, NVPTX] Codegen for critical construct.

Added correct codegen for the critical construct on NVPTX devices.

llvm-svn: 331652

2 files changed, 70 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
index 9e6f2b4b9a3..19b3147d26b 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
@@ -1837,6 +1837,66 @@ void CGOpenMPRuntimeNVPTX::emitSpmdParallelCall(
   emitOutlinedFunctionCall(CGF, Loc, OutlinedFn, OutlinedFnArgs);
 }
 
+void CGOpenMPRuntimeNVPTX::emitCriticalRegion(
+    CodeGenFunction &CGF, StringRef CriticalName,
+    const RegionCodeGenTy &CriticalOpGen, SourceLocation Loc,
+    const Expr *Hint) {
+  llvm::BasicBlock *LoopBB = CGF.createBasicBlock("omp.critical.loop");
+  llvm::BasicBlock *TestBB = CGF.createBasicBlock("omp.critical.test");
+  llvm::BasicBlock *SyncBB = CGF.createBasicBlock("omp.critical.sync");
+  llvm::BasicBlock *BodyBB = CGF.createBasicBlock("omp.critical.body");
+  llvm::BasicBlock *ExitBB = CGF.createBasicBlock("omp.critical.exit");
+
+  // Fetch team-local id of the thread.
+  llvm::Value *ThreadID = getNVPTXThreadID(CGF);
+
+  // Get the width of the team.
+  llvm::Value *TeamWidth = getNVPTXNumThreads(CGF);
+
+  // Initialize the counter variable for the loop.
+  QualType Int32Ty =
+      CGF.getContext().getIntTypeForBitwidth(/*DestWidth=*/32, /*Signed=*/0);
+  Address Counter = CGF.CreateMemTemp(Int32Ty, "critical_counter");
+  LValue CounterLVal = CGF.MakeAddrLValue(Counter, Int32Ty);
+  CGF.EmitStoreOfScalar(llvm::Constant::getNullValue(CGM.Int32Ty), CounterLVal,
+                        /*isInit=*/true);
+
+  // Block checks if loop counter exceeds upper bound.
+  CGF.EmitBlock(LoopBB);
+  llvm::Value *CounterVal = CGF.EmitLoadOfScalar(CounterLVal, Loc);
+  llvm::Value *CmpLoopBound = CGF.Builder.CreateICmpSLT(CounterVal, TeamWidth);
+  CGF.Builder.CreateCondBr(CmpLoopBound, TestBB, ExitBB);
+
+  // Block tests which single thread should execute region, and which threads
+  // should go straight to synchronisation point.
+  CGF.EmitBlock(TestBB);
+  CounterVal = CGF.EmitLoadOfScalar(CounterLVal, Loc);
+  llvm::Value *CmpThreadToCounter =
+      CGF.Builder.CreateICmpEQ(ThreadID, CounterVal);
+  CGF.Builder.CreateCondBr(CmpThreadToCounter, BodyBB, SyncBB);
+
+  // Block emits the body of the critical region.
+  CGF.EmitBlock(BodyBB);
+
+  // Output the critical statement.
+  CriticalOpGen(CGF);
+
+  // After the body surrounded by the critical region, the single executing
+  // thread will jump to the synchronisation point.
+  // Block waits for all threads in current team to finish then increments the
+  // counter variable and returns to the loop.
+  CGF.EmitBlock(SyncBB);
+  getNVPTXCTABarrier(CGF);
+
+  llvm::Value *IncCounterVal =
+      CGF.Builder.CreateNSWAdd(CounterVal, CGF.Builder.getInt32(1));
+  CGF.EmitStoreOfScalar(IncCounterVal, CounterLVal);
+  CGF.EmitBranch(LoopBB);
+
+  // Block that is reached when  all threads in the team complete the region.
+  CGF.EmitBlock(ExitBB, /*IsFinished=*/true);
+}
+
 /// Cast value to the specified type.
 static llvm::Value *castValueToType(CodeGenFunction &CGF, llvm::Value *Val,
                                     QualType ValTy, QualType CastTy,
diff --git a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.h b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.h
index a5f39c28a7a..ac8011dc790 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.h
+++ b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.h
@@ -250,6 +250,16 @@ public:
                         ArrayRef<llvm::Value *> CapturedVars,
                         const Expr *IfCond) override;
 
+  /// Emits a critical region.
+  /// \param CriticalName Name of the critical region.
+  /// \param CriticalOpGen Generator for the statement associated with the given
+  /// critical region.
+  /// \param Hint Value of the 'hint' clause (optional).
+  void emitCriticalRegion(CodeGenFunction &CGF, StringRef CriticalName,
+                          const RegionCodeGenTy &CriticalOpGen,
+                          SourceLocation Loc,
+                          const Expr *Hint = nullptr) override;
+
   /// Emit a code for reduction clause.
   ///
   /// \param Privates List of private copies for original reduction arguments.