Pass DebugLoc and SDLoc by const ref.

This used to be free, copying and moving DebugLocs became expensive
after the metadata rewrite. Passing by reference eliminates a ton of
track/untrack operations. No functionality change intended.

llvm-svn: 272512
diff --git a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
index c6bc6f8..8cbd2d5 100644
--- a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
@@ -1077,7 +1077,7 @@
 }
 
 SDValue R600TargetLowering::LowerImplicitParameter(SelectionDAG &DAG, EVT VT,
-                                                   SDLoc DL,
+                                                   const SDLoc &DL,
                                                    unsigned DwordOffset) const {
   unsigned ByteOffset = DwordOffset * 4;
   PointerType * PtrType = PointerType::get(VT.getTypeForEVT(*DAG.getContext()),
@@ -1747,12 +1747,9 @@
 /// every function is a kernel function, but in the future we should use
 /// separate calling conventions for kernel and non-kernel functions.
 SDValue R600TargetLowering::LowerFormalArguments(
-                                      SDValue Chain,
-                                      CallingConv::ID CallConv,
-                                      bool isVarArg,
-                                      const SmallVectorImpl<ISD::InputArg> &Ins,
-                                      SDLoc DL, SelectionDAG &DAG,
-                                      SmallVectorImpl<SDValue> &InVals) const {
+    SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
+    const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &DL,
+    SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(), ArgLocs,
                  *DAG.getContext());
@@ -1931,10 +1928,9 @@
                             NewBldVec);
 }
 
-
-SDValue R600TargetLowering::OptimizeSwizzle(SDValue BuildVector,
-                                            SDValue Swz[4], SelectionDAG &DAG,
-                                            SDLoc DL) const {
+SDValue R600TargetLowering::OptimizeSwizzle(SDValue BuildVector, SDValue Swz[4],
+                                            SelectionDAG &DAG,
+                                            const SDLoc &DL) const {
   assert(BuildVector.getOpcode() == ISD::BUILD_VECTOR);
   // Old -> New swizzle values
   DenseMap<unsigned, unsigned> SwizzleRemap;