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/WebAssembly/WebAssemblyFrameLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
index 24112d5..0a5782e 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
@@ -81,7 +81,7 @@
                             MachineBasicBlock &MBB,
                             MachineBasicBlock::iterator &InsertAddr,
                             MachineBasicBlock::iterator &InsertStore,
-                            DebugLoc DL) {
+                            const DebugLoc &DL) {
   const char *ES = "__stack_pointer";
   auto *SPSymbol = MF.createExternalSymbolName(ES);
   MachineRegisterInfo &MRI = MF.getRegInfo();