AArch64: implement large code model access to global variables.

The MOVZ/MOVK instruction sequence may not be the most efficient (a
literal-pool load could be better) but adding that would require
reinstating the ConstantIslands pass.

For now the sequence is correct, and that's enough. Beware, as of
commit GNU ld does not appear to support the relocations needed for
this. Its primary purpose (for now) will be to support JITed code,
since in that case there is no guarantee of where your code will end
up in memory relative to external symbols it references.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181117 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp b/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
index 468c56156a..863cf6f857 100644
--- a/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
+++ b/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
@@ -70,6 +70,15 @@ public:
     return SelectCVTFixedPosOperand(N, FixedPos, RegWidth);
   }
 
+  /// Used for pre-lowered address-reference nodes, so we already know
+  /// the fields match. This operand's job is simply to add an
+  /// appropriate shift operand (i.e. 0) to the MOVZ/MOVK instruction.
+  bool SelectMOVWAddressRef(SDValue N, SDValue &Imm, SDValue &Shift) {
+    Imm = N;
+    Shift = CurDAG->getTargetConstant(0, MVT::i32);
+    return true;
+  }
+
   bool SelectFPZeroOperand(SDValue N, SDValue &Dummy);
 
   bool SelectCVTFixedPosOperand(SDValue N, SDValue &FixedPos,