Add XCore support for ATOMIC_FENCE.

ATOMIC_FENCE is lowered to a compiler barrier which is codegen only. There
is no need to emit an instructions since the XCore provides sequential
consistency.

Original patch by Richard Osborne

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194464 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/XCore/XCoreISelLowering.cpp

@@ -59,6 +59,7 @@ getTargetNodeName(unsigned Opcode) const
     case XCoreISD::CRC8              : return "XCoreISD::CRC8";
     case XCoreISD::BR_JT             : return "XCoreISD::BR_JT";
     case XCoreISD::BR_JT32           : return "XCoreISD::BR_JT32";
+    case XCoreISD::MEMBARRIER        : return "XCoreISD::MEMBARRIER";
     default                          : return NULL;
   }
 }
@@ -148,6 +149,9 @@ XCoreTargetLowering::XCoreTargetLowering(XCoreTargetMachine &XTM)
   setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32, Expand);
 
+  // Atomic operations
+  setOperationAction(ISD::ATOMIC_FENCE, MVT::Other, Custom);
+
   // TRAMPOLINE is custom lowered.
   setOperationAction(ISD::INIT_TRAMPOLINE, MVT::Other, Custom);
   setOperationAction(ISD::ADJUST_TRAMPOLINE, MVT::Other, Custom);
@@ -206,6 +210,7 @@ LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::INIT_TRAMPOLINE:    return LowerINIT_TRAMPOLINE(Op, DAG);
   case ISD::ADJUST_TRAMPOLINE:  return LowerADJUST_TRAMPOLINE(Op, DAG);
   case ISD::INTRINSIC_WO_CHAIN: return LowerINTRINSIC_WO_CHAIN(Op, DAG);
+  case ISD::ATOMIC_FENCE:       return LowerATOMIC_FENCE(Op, DAG);
   default:
     llvm_unreachable("unimplemented operand");
   }
@@ -847,6 +852,12 @@ LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const {
   return SDValue();
 }
 
+SDValue XCoreTargetLowering::
+LowerATOMIC_FENCE(SDValue Op, SelectionDAG &DAG) const {
+  SDLoc DL(Op);
+  return DAG.getNode(XCoreISD::MEMBARRIER, DL, MVT::Other, Op.getOperand(0));
+}
+
 //===----------------------------------------------------------------------===//
 //                      Calling Convention Implementation
 //===----------------------------------------------------------------------===//

lib/Target/XCore/XCoreISelLowering.h

@@ -70,7 +70,10 @@ namespace llvm {
       BR_JT,
 
       // Jumptable branch using long branches for each entry.
-      BR_JT32
+      BR_JT32,
+
+      // Memory barrier.
+      MEMBARRIER
     };
   }
 
@@ -158,6 +161,7 @@ namespace llvm {
     SDValue LowerINIT_TRAMPOLINE(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerADJUST_TRAMPOLINE(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const;
+    SDValue LowerATOMIC_FENCE(SDValue Op, SelectionDAG &DAG) const;
 
     // Inline asm support
     std::pair<unsigned, const TargetRegisterClass*>

lib/Target/XCore/XCoreInstrInfo.td

@@ -70,6 +70,11 @@ def callseq_start : SDNode<"ISD::CALLSEQ_START", SDT_XCoreCallSeqStart,
 def callseq_end   : SDNode<"ISD::CALLSEQ_END",   SDT_XCoreCallSeqEnd,
                            [SDNPHasChain, SDNPOptInGlue, SDNPOutGlue]>;
 
+def SDT_XCoreMEMBARRIER : SDTypeProfile<0, 0, []>;
+
+def XCoreMemBarrier : SDNode<"XCoreISD::MEMBARRIER", SDT_XCoreMEMBARRIER,
+                             [SDNPHasChain]>;
+
 //===----------------------------------------------------------------------===//
 // Instruction Pattern Stuff
 //===----------------------------------------------------------------------===//
@@ -343,6 +348,10 @@ let usesCustomInserter = 1 in {
                                  (select GRRegs:$cond, GRRegs:$T, GRRegs:$F))]>;
 }
 
+let hasSideEffects = 1 in
+def Int_MemBarrier : PseudoInstXCore<(outs), (ins), "#MEMBARRIER",
+                                     [(XCoreMemBarrier)]>;
+
 //===----------------------------------------------------------------------===//
 // Instructions
 //===----------------------------------------------------------------------===//

test/CodeGen/XCore/atomic.ll

@@ -0,0 +1,16 @@
+; RUN: llc < %s -march=xcore | FileCheck %s
+
+; CHECK-LABEL: atomic_fence
+; CHECK: #MEMBARRIER
+; CHECK: #MEMBARRIER
+; CHECK: #MEMBARRIER
+; CHECK: #MEMBARRIER
+; CHECK: retsp 0
+define void @atomic_fence() nounwind {
+entry:
+  fence acquire
+  fence release
+  fence acq_rel
+  fence seq_cst
+  ret void
+}