ARM: support PIC on Windows on ARM

Handle lowering of global addresses for PIC mode compilation on Windows.  Always
use the movw/movt load to load the address as Windows on ARM requires ARMv7+ and
is a pure Thumb environment.

llvm-svn: 208385

1 files changed, 26 insertions, 2 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 8f410b702c5..925b4693fd5 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -2485,6 +2485,23 @@ SDValue ARMTargetLowering::LowerGlobalAddressDarwin(SDValue Op,
   return Result;
 }
 
+SDValue ARMTargetLowering::LowerGlobalAddressWindows(SDValue Op,
+                                                     SelectionDAG &DAG) const {
+  assert(Subtarget->isTargetWindows() && "non-Windows COFF is not supported");
+  assert(Subtarget->useMovt() && "Windows on ARM expects to use movw/movt");
+
+  const GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
+  EVT PtrVT = getPointerTy();
+  SDLoc DL(Op);
+
+  ++NumMovwMovt;
+
+  // FIXME: Once remat is capable of dealing with instructions with register
+  // operands, expand this into two nodes.
+  return DAG.getNode(ARMISD::Wrapper, DL, PtrVT,
+                     DAG.getTargetGlobalAddress(GV, DL, PtrVT));
+}
+
 SDValue ARMTargetLowering::LowerGLOBAL_OFFSET_TABLE(SDValue Op,
                                                     SelectionDAG &DAG) const {
   assert(Subtarget->isTargetELF() &&
@@ -6050,8 +6067,15 @@ SDValue ARMTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::ConstantPool:  return LowerConstantPool(Op, DAG);
   case ISD::BlockAddress:  return LowerBlockAddress(Op, DAG);
   case ISD::GlobalAddress:
-    return Subtarget->isTargetMachO() ? LowerGlobalAddressDarwin(Op, DAG) :
-      LowerGlobalAddressELF(Op, DAG);
+    switch (Subtarget->getTargetTriple().getObjectFormat()) {
+    default: llvm_unreachable("unknown object format");
+    case Triple::COFF:
+      return LowerGlobalAddressWindows(Op, DAG);
+    case Triple::ELF:
+      return LowerGlobalAddressELF(Op, DAG);
+    case Triple::MachO:
+      return LowerGlobalAddressDarwin(Op, DAG);
+    }
   case ISD::GlobalTLSAddress: return LowerGlobalTLSAddress(Op, DAG);
   case ISD::SELECT:        return LowerSELECT(Op, DAG);
   case ISD::SELECT_CC:     return LowerSELECT_CC(Op, DAG);