[ARM] Place jump table as the first operand in additions

When generating table jump code for switch statements, place the jump
table label as the first operand in the various addition instructions
in order to enable addressing mode selectors to better match index
computation and possibly fold them into the addressing mode of the
table entry load instruction.

Differential revision: https://reviews.llvm.org/D39752

llvm-svn: 318033

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index deece84ecf2..135e20cf22f 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -4517,7 +4517,7 @@ SDValue ARMTargetLowering::LowerBR_JT(SDValue Op, SelectionDAG &DAG) const {
   SDValue JTI = DAG.getTargetJumpTable(JT->getIndex(), PTy);
   Table = DAG.getNode(ARMISD::WrapperJT, dl, MVT::i32, JTI);
   Index = DAG.getNode(ISD::MUL, dl, PTy, Index, DAG.getConstant(4, dl, PTy));
-  SDValue Addr = DAG.getNode(ISD::ADD, dl, PTy, Index, Table);
+  SDValue Addr = DAG.getNode(ISD::ADD, dl, PTy, Table, Index);
   if (Subtarget->isThumb2() || (Subtarget->hasV8MBaselineOps() && Subtarget->isThumb())) {
     // Thumb2 and ARMv8-M use a two-level jump. That is, it jumps into the jump table
     // which does another jump to the destination. This also makes it easier
@@ -4531,7 +4531,7 @@ SDValue ARMTargetLowering::LowerBR_JT(SDValue Op, SelectionDAG &DAG) const {
         DAG.getLoad((EVT)MVT::i32, dl, Chain, Addr,
                     MachinePointerInfo::getJumpTable(DAG.getMachineFunction()));
     Chain = Addr.getValue(1);
-    Addr = DAG.getNode(ISD::ADD, dl, PTy, Addr, Table);
+    Addr = DAG.getNode(ISD::ADD, dl, PTy, Table, Addr);
     return DAG.getNode(ARMISD::BR_JT, dl, MVT::Other, Chain, Addr, JTI);
   } else {
     Addr =