[ARM] Improve codegen of volatile load/store of i64

Summary:
Instead of generating two i32 instructions for each load or store of a volatile
i64 value (two LDRs or STRs), now emit LDRD/STRD.

These improvements cover architectures implementing ARMv5TE or Thumb-2.

Reviewers: dmgreen, efriedma, john.brawn

Reviewed By: efriedma

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70072

1 files changed, 49 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 1f998defbd1..dcdec779bbe 100644
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -145,6 +145,8 @@ public:
 
   // Thumb 2 Addressing Modes:
   bool SelectT2AddrModeImm12(SDValue N, SDValue &Base, SDValue &OffImm);
+  template <unsigned Shift>
+  bool SelectT2AddrModeImm8(SDValue N, SDValue &Base, SDValue &OffImm);
   bool SelectT2AddrModeImm8(SDValue N, SDValue &Base,
                             SDValue &OffImm);
   bool SelectT2AddrModeImm8Offset(SDNode *Op, SDValue N,
@@ -1294,6 +1296,33 @@ bool ARMDAGToDAGISel::SelectT2AddrModeImm12(SDValue N,
   return true;
 }
 
+template <unsigned Shift>
+bool ARMDAGToDAGISel::SelectT2AddrModeImm8(SDValue N, SDValue &Base,
+                                           SDValue &OffImm) {
+  if (N.getOpcode() == ISD::SUB || CurDAG->isBaseWithConstantOffset(N)) {
+    int RHSC;
+    if (isScaledConstantInRange(N.getOperand(1), 1 << Shift, -255, 256, RHSC)) {
+      Base = N.getOperand(0);
+      if (Base.getOpcode() == ISD::FrameIndex) {
+        int FI = cast<FrameIndexSDNode>(Base)->getIndex();
+        Base = CurDAG->getTargetFrameIndex(
+            FI, TLI->getPointerTy(CurDAG->getDataLayout()));
+      }
+
+      if (N.getOpcode() == ISD::SUB)
+        RHSC = -RHSC;
+      OffImm =
+          CurDAG->getTargetConstant(RHSC * (1 << Shift), SDLoc(N), MVT::i32);
+      return true;
+    }
+  }
+
+  // Base only.
+  Base = N;
+  OffImm = CurDAG->getTargetConstant(0, SDLoc(N), MVT::i32);
+  return true;
+}
+
 bool ARMDAGToDAGISel::SelectT2AddrModeImm8(SDValue N,
                                            SDValue &Base, SDValue &OffImm) {
   // Match simple R - imm8 operands.
@@ -3486,6 +3515,26 @@ void ARMDAGToDAGISel::Select(SDNode *N) {
     CurDAG->RemoveDeadNode(N);
     return;
   }
+  case ARMISD::LDRD: {
+    if (Subtarget->isThumb2())
+      break; // TableGen handles isel in this case.
+    SDValue Base, RegOffset, ImmOffset;
+    const SDValue &Chain = N->getOperand(0);
+    const SDValue &Addr = N->getOperand(1);
+    SelectAddrMode3(Addr, Base, RegOffset, ImmOffset);
+    SDValue Ops[] = {Base, RegOffset, ImmOffset, Chain};
+    SDNode *New = CurDAG->getMachineNode(ARM::LOADDUAL, dl,
+                                         {MVT::Untyped, MVT::Other}, Ops);
+    SDValue Lo = CurDAG->getTargetExtractSubreg(ARM::gsub_0, dl, MVT::i32,
+                                                SDValue(New, 0));
+    SDValue Hi = CurDAG->getTargetExtractSubreg(ARM::gsub_1, dl, MVT::i32,
+                                                SDValue(New, 0));
+    ReplaceUses(SDValue(N, 0), Lo);
+    ReplaceUses(SDValue(N, 1), Hi);
+    ReplaceUses(SDValue(N, 2), SDValue(New, 1));
+    CurDAG->RemoveDeadNode(N);
+    return;
+  }
   case ARMISD::LOOP_DEC: {
     SDValue Ops[] = { N->getOperand(1),
                       N->getOperand(2),