[WebAssembly] Insert COPY_LOCAL between CopyToReg and FrameIndex DAG nodes

CopyToReg nodes don't support FrameIndex operands. Other targets select
the FI to some LEA-like instruction, but since we don't have that, we
need to insert some kind of instruction that can take an FI operand and
produces a value usable by CopyToReg (i.e. in a vreg). So insert a dummy
copy_local between Op and its FI operand. This results in a redundant
copy which we should optimize away later (maybe in the post-FI-lowering
peephole pass).

Differential Revision: http://reviews.llvm.org/D17213

llvm-svn: 260987

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 436494efd23..2027e8ba678 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -114,6 +114,7 @@ WebAssemblyTargetLowering::WebAssemblyTargetLowering(
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVTPtr, Expand);
 
   setOperationAction(ISD::FrameIndex, MVT::i32, Custom);
+  setOperationAction(ISD::CopyToReg, MVT::Other, Custom);
 
   // Expand these forms; we pattern-match the forms that we can handle in isel.
   for (auto T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
@@ -544,9 +545,34 @@ SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op,
     case ISD::FRAMEADDR: // TODO: Make this return the userspace frame address
       fail(DL, DAG, "WebAssembly hasn't implemented __builtin_frame_address");
       return SDValue();
+    case ISD::CopyToReg:
+      return LowerCopyToReg(Op, DAG);
   }
 }
 
+SDValue WebAssemblyTargetLowering::LowerCopyToReg(SDValue Op,
+                                                  SelectionDAG &DAG) const {
+  SDValue Src = Op.getOperand(2);
+  if (isa<FrameIndexSDNode>(Src.getNode())) {
+    // CopyToReg nodes don't support FrameIndex operands. Other targets select
+    // the FI to some LEA-like instruction, but since we don't have that, we
+    // need to insert some kind of instruction that can take an FI operand and
+    // produces a value usable by CopyToReg (i.e. in a vreg). So insert a dummy
+    // copy_local between Op and its FI operand.
+    SDLoc DL(Op);
+    EVT VT = Src.getValueType();
+    SDValue Copy(
+        DAG.getMachineNode(VT == MVT::i32 ? WebAssembly::COPY_LOCAL_I32
+                                          : WebAssembly::COPY_LOCAL_I64,
+                           DL, VT, Src),
+        0);
+    return DAG.getCopyToReg(Op.getOperand(0), DL,
+                            cast<RegisterSDNode>(Op.getOperand(1))->getReg(),
+                            Copy);
+  }
+  return SDValue();
+}
+
 SDValue WebAssemblyTargetLowering::LowerFrameIndex(SDValue Op,
                                                    SelectionDAG &DAG) const {
   int FI = cast<FrameIndexSDNode>(Op)->getIndex();