ARM: fix big-endian 64-bit cmpxchg.

On big-endian machines the high and low parts of the value accessed by ldrexd
and strexd are swapped around. To account for this we swap inputs and outputs
in ISelLowering.

Patch by Bharathi Seshadri.

llvm-svn: 306865

1 files changed, 11 insertions, 4 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 2bcc707e9fc..e42514acd76 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -7580,6 +7580,9 @@ static SDValue createGPRPairNode(SelectionDAG &DAG, SDValue V) {
   SDValue VHi = DAG.getAnyExtOrTrunc(
       DAG.getNode(ISD::SRL, dl, MVT::i64, V, DAG.getConstant(32, dl, MVT::i32)),
       dl, MVT::i32);
+  bool isBigEndian = DAG.getDataLayout().isBigEndian();
+  if (isBigEndian)
+    std::swap (VLo, VHi);
   SDValue RegClass =
       DAG.getTargetConstant(ARM::GPRPairRegClassID, dl, MVT::i32);
   SDValue SubReg0 = DAG.getTargetConstant(ARM::gsub_0, dl, MVT::i32);
@@ -7607,10 +7610,14 @@ static void ReplaceCMP_SWAP_64Results(SDNode *N,
   MemOp[0] = cast<MemSDNode>(N)->getMemOperand();
   cast<MachineSDNode>(CmpSwap)->setMemRefs(MemOp, MemOp + 1);
 
-  Results.push_back(DAG.getTargetExtractSubreg(ARM::gsub_0, SDLoc(N), MVT::i32,
-                                               SDValue(CmpSwap, 0)));
-  Results.push_back(DAG.getTargetExtractSubreg(ARM::gsub_1, SDLoc(N), MVT::i32,
-                                               SDValue(CmpSwap, 0)));
+  bool isBigEndian = DAG.getDataLayout().isBigEndian();
+
+  Results.push_back(
+      DAG.getTargetExtractSubreg(isBigEndian ? ARM::gsub_1 : ARM::gsub_0,
+                                 SDLoc(N), MVT::i32, SDValue(CmpSwap, 0)));
+  Results.push_back(
+      DAG.getTargetExtractSubreg(isBigEndian ? ARM::gsub_0 : ARM::gsub_1,
+                                 SDLoc(N), MVT::i32, SDValue(CmpSwap, 0)));
   Results.push_back(SDValue(CmpSwap, 2));
 }