[XRay] ARM 32-bit no-Thumb support in LLVM

This is a port of XRay to ARM 32-bit, without Thumb support yet. The XRay instrumentation support is moving up to AsmPrinter.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:

1. https://reviews.llvm.org/D23932 (Clang test)
2. https://reviews.llvm.org/D23933 (compiler-rt)

Differential Revision: https://reviews.llvm.org/D23931

llvm-svn: 280888
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 0fed4e9..ccc1691 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2606,3 +2606,13 @@
 AsmPrinterHandler::~AsmPrinterHandler() {}
 
 void AsmPrinterHandler::markFunctionEnd() {}
+
+void AsmPrinter::recordSled(MCSymbol *Sled, const MachineInstr &MI,
+  SledKind Kind) {
+  auto Fn = MI.getParent()->getParent()->getFunction();
+  auto Attr = Fn->getFnAttribute("function-instrument");
+  bool AlwaysInstrument =
+    Attr.isStringAttribute() && Attr.getValueAsString() == "xray-always";
+  Sleds.emplace_back(
+    XRayFunctionEntry{ Sled, CurrentFnSym, Kind, AlwaysInstrument, Fn });
+}