AM2 can match 2^n +/- 1. e.g. ldr r3, [r2, r2, lsl #2]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35088 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index c9642ca..b0c040b 100644
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -102,6 +102,29 @@
bool ARMDAGToDAGISel::SelectAddrMode2(SDOperand Op, SDOperand N,
SDOperand &Base, SDOperand &Offset,
SDOperand &Opc) {
+ if (N.getOpcode() == ISD::MUL) {
+ if (ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(N.getOperand(1))) {
+ // X * [3,5,9] -> X + X * [2,4,8] etc.
+ int RHSC = (int)RHS->getValue();
+ if (RHSC & 1) {
+ RHSC = RHSC & ~1;
+ ARM_AM::AddrOpc AddSub = ARM_AM::add;
+ if (RHSC < 0) {
+ AddSub = ARM_AM::sub;
+ RHSC = - RHSC;
+ }
+ if (isPowerOf2_32(RHSC)) {
+ unsigned ShAmt = Log2_32(RHSC);
+ Base = Offset = N.getOperand(0);
+ Opc = CurDAG->getTargetConstant(ARM_AM::getAM2Opc(AddSub, ShAmt,
+ ARM_AM::lsl),
+ MVT::i32);
+ return true;
+ }
+ }
+ }
+ }
+
if (N.getOpcode() != ISD::ADD && N.getOpcode() != ISD::SUB) {
Base = N;
if (N.getOpcode() == ISD::FrameIndex) {