AArch64: add a pass to compress jump-table entries when possible.

llvm-svn: 345188

1 files changed, 19 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index fea1531540f..c8227cd139a 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -187,7 +187,7 @@ AArch64TargetLowering::AArch64TargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::SELECT_CC, MVT::f16, Custom);
   setOperationAction(ISD::SELECT_CC, MVT::f32, Custom);
   setOperationAction(ISD::SELECT_CC, MVT::f64, Custom);
-  setOperationAction(ISD::BR_JT, MVT::Other, Expand);
+  setOperationAction(ISD::BR_JT, MVT::Other, Custom);
   setOperationAction(ISD::JumpTable, MVT::i64, Custom);
 
   setOperationAction(ISD::SHL_PARTS, MVT::i64, Custom);
@@ -2825,6 +2825,8 @@ SDValue AArch64TargetLowering::LowerOperation(SDValue Op,
     return LowerSELECT_CC(Op, DAG);
   case ISD::JumpTable:
     return LowerJumpTable(Op, DAG);
+  case ISD::BR_JT:
+    return LowerBR_JT(Op, DAG);
   case ISD::ConstantPool:
     return LowerConstantPool(Op, DAG);
   case ISD::BlockAddress:
@@ -4902,6 +4904,22 @@ SDValue AArch64TargetLowering::LowerJumpTable(SDValue Op,
   return getAddr(JT, DAG);
 }
 
+SDValue AArch64TargetLowering::LowerBR_JT(SDValue Op,
+                                          SelectionDAG &DAG) const {
+  // Jump table entries as PC relative offsets. No additional tweaking
+  // is necessary here. Just get the address of the jump table.
+  SDLoc DL(Op);
+  SDValue JT = Op.getOperand(1);
+  SDValue Entry = Op.getOperand(2);
+  int JTI = cast<JumpTableSDNode>(JT.getNode())->getIndex();
+
+  SDNode *Dest =
+      DAG.getMachineNode(AArch64::JumpTableDest32, DL, MVT::i64, MVT::i64, JT,
+                         Entry, DAG.getTargetJumpTable(JTI, MVT::i32));
+  return DAG.getNode(ISD::BRIND, DL, MVT::Other, Op.getOperand(0),
+                     SDValue(Dest, 0));
+}
+
 SDValue AArch64TargetLowering::LowerConstantPool(SDValue Op,
                                                  SelectionDAG &DAG) const {
   ConstantPoolSDNode *CP = cast<ConstantPoolSDNode>(Op);