[XRay] Allow logging the first argument of a function call.

Summary:
Functions with the "xray-log-args" attribute will have a special XRay sled kind
emitted, for compiler-rt to copy any call arguments to your logging handler.

For practical and performance reasons, only the first argument is supported, and
only up to 64 bits.

Reviewers: dberris

Reviewed By: dberris

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29702

llvm-svn: 296998

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index b8a8a999c42..7099065a638 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2756,8 +2756,11 @@ void AsmPrinter::recordSled(MCSymbol *Sled, const MachineInstr &MI,
   SledKind Kind) {
   auto Fn = MI.getParent()->getParent()->getFunction();
   auto Attr = Fn->getFnAttribute("function-instrument");
+  bool LogArgs = Fn->hasFnAttribute("xray-log-args");
   bool AlwaysInstrument =
     Attr.isStringAttribute() && Attr.getValueAsString() == "xray-always";
+  if (Kind == SledKind::FUNCTION_ENTER && LogArgs)
+    Kind = SledKind::LOG_ARGS_ENTER;
   Sleds.emplace_back(
     XRayFunctionEntry{ Sled, CurrentFnSym, Kind, AlwaysInstrument, Fn });
 }