Some improvements to the handling of C11 atomic types:

- Add atomic-to/from-nonatomic cast types
- Emit atomic operations for arithmetic on atomic types
- Emit non-atomic stores for initialisation of atomic types, but atomic stores and loads for every other store / load
- Add a __atomic_init() intrinsic which does a non-atomic store to an _Atomic() type.  This is needed for the corresponding C11 stdatomic.h function.
- Enables the relevant __has_feature() checks.  The feature isn't 100% complete yet, but it's done enough that we want people testing it.

Still to do:

- Make the arithmetic operations on atomic types (e.g. Atomic(int) foo = 1; foo++;) use the correct LLVM intrinsic if one exists, not a loop with a cmpxchg.
- Add a signal fence builtin
- Properly set the fenv state in atomic operations on floating point values
- Correctly handle things like _Atomic(_Complex double) which are too large for an atomic cmpxchg on some platforms (this requires working out what 'correctly' means in this context)
- Fix the many remaining corner cases



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148242 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 52 insertions, 0 deletions

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index c2aec36ee8..8087c3b802 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -1064,6 +1064,8 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     Value *Src = Visit(const_cast<Expr*>(E));
     return Builder.CreateBitCast(Src, ConvertType(DestTy));
   }
+  case CK_AtomicToNonAtomic:
+  case CK_NonAtomicToAtomic:
   case CK_NoOp:
   case CK_UserDefinedConversion:
     return Visit(const_cast<Expr*>(E));
@@ -1293,9 +1295,21 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
   QualType type = E->getSubExpr()->getType();
   llvm::Value *value = EmitLoadOfLValue(LV);
   llvm::Value *input = value;
+  llvm::PHINode *atomicPHI = 0;
 
   int amount = (isInc ? 1 : -1);
 
+  if (const AtomicType *atomicTy = type->getAs<AtomicType>()) {
+    llvm::BasicBlock *startBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *opBB = CGF.createBasicBlock("atomic_op", CGF.CurFn);
+    Builder.CreateBr(opBB);
+    Builder.SetInsertPoint(opBB);
+    atomicPHI = Builder.CreatePHI(value->getType(), 2);
+    atomicPHI->addIncoming(value, startBB);
+    type = atomicTy->getValueType();
+    value = atomicPHI;
+  }
+
   // Special case of integer increment that we have to check first: bool++.
   // Due to promotion rules, we get:
   //   bool++ -> bool = bool + 1
@@ -1415,6 +1429,18 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
       value = Builder.CreateInBoundsGEP(value, sizeValue, "incdec.objptr");
     value = Builder.CreateBitCast(value, input->getType());
   }
+  
+  if (atomicPHI) {
+    llvm::BasicBlock *opBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
+    llvm::Value *old = Builder.CreateAtomicCmpXchg(LV.getAddress(), atomicPHI,
+        value, llvm::SequentiallyConsistent);
+    atomicPHI->addIncoming(old, opBB);
+    llvm::Value *success = Builder.CreateICmpEQ(old, atomicPHI);
+    Builder.CreateCondBr(success, contBB, opBB);
+    Builder.SetInsertPoint(contBB);
+    return isPre ? value : input;
+  }
 
   // Store the updated result through the lvalue.
   if (LV.isBitField())
@@ -1670,12 +1696,38 @@ LValue ScalarExprEmitter::EmitCompoundAssignLValue(
   OpInfo.LHS = EmitLoadOfLValue(LHSLV);
   OpInfo.LHS = EmitScalarConversion(OpInfo.LHS, LHSTy,
                                     E->getComputationLHSType());
+
+  llvm::PHINode *atomicPHI = 0;
+  if (const AtomicType *atomicTy = OpInfo.Ty->getAs<AtomicType>()) {
+    // FIXME: For floating point types, we should be saving and restoring the
+    // floating point environment in the loop.
+    llvm::BasicBlock *startBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *opBB = CGF.createBasicBlock("atomic_op", CGF.CurFn);
+    Builder.CreateBr(opBB);
+    Builder.SetInsertPoint(opBB);
+    atomicPHI = Builder.CreatePHI(OpInfo.LHS->getType(), 2);
+    atomicPHI->addIncoming(OpInfo.LHS, startBB);
+    OpInfo.Ty = atomicTy->getValueType();
+    OpInfo.LHS = atomicPHI;
+  }
   
   // Expand the binary operator.
   Result = (this->*Func)(OpInfo);
   
   // Convert the result back to the LHS type.
   Result = EmitScalarConversion(Result, E->getComputationResultType(), LHSTy);
+
+  if (atomicPHI) {
+    llvm::BasicBlock *opBB = Builder.GetInsertBlock();
+    llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
+    llvm::Value *old = Builder.CreateAtomicCmpXchg(LHSLV.getAddress(), atomicPHI,
+        Result, llvm::SequentiallyConsistent);
+    atomicPHI->addIncoming(old, opBB);
+    llvm::Value *success = Builder.CreateICmpEQ(old, atomicPHI);
+    Builder.CreateCondBr(success, contBB, opBB);
+    Builder.SetInsertPoint(contBB);
+    return LHSLV;
+  }
   
   // Store the result value into the LHS lvalue. Bit-fields are handled
   // specially because the result is altered by the store, i.e., [C99 6.5.16p1]