AMDGPU: Pass function directly instead of MachineFunction

These functions just query the underlying IR function,
so pass it directly.

llvm-svn: 333442
diff --git a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
index 75cefdc..e3768ae 100644
--- a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
@@ -1596,7 +1596,8 @@
 
     unsigned ValBase = ArgLocs[In.getOrigArgIndex()].getLocMemOffset();
     unsigned PartOffset = VA.getLocMemOffset();
-    unsigned Offset = Subtarget->getExplicitKernelArgOffset(MF) + VA.getLocMemOffset();
+    unsigned Offset = Subtarget->getExplicitKernelArgOffset(MF.getFunction()) +
+                      VA.getLocMemOffset();
 
     MachinePointerInfo PtrInfo(UndefValue::get(PtrTy), PartOffset - ValBase);
     SDValue Arg = DAG.getLoad(