[xray] Option to omit the function index

Summary:
Add a flag to omit the xray_fn_idx to cut size overhead and relocations
roughly in half at the cost of reduced performance for single function
patching.  Minor additions to compiler-rt support per-function patching
without the index.

Reviewers: dberris, MaskRay, johnislarry

Subscribers: hiraditya, arphaman, cfe-commits, #sanitizers, llvm-commits

Tags: #clang, #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D81995

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CommandFlags.cpp b/llvm/lib/CodeGen/CommandFlags.cpp
index 947ae32..12dadf9 100644
--- a/llvm/lib/CodeGen/CommandFlags.cpp
+++ b/llvm/lib/CodeGen/CommandFlags.cpp
@@ -86,6 +86,7 @@ CGOPT(bool, EnableAddrsig)
 CGOPT(bool, EmitCallSiteInfo)
 CGOPT(bool, EnableDebugEntryValues)
 CGOPT(bool, ForceDwarfFrameSection)
+CGOPT(bool, XRayOmitFunctionIndex)
 
 codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
 #define CGBINDOPT(NAME)                                                        \
@@ -404,6 +405,11 @@ codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
       cl::desc("Always emit a debug frame section."), cl::init(false));
   CGBINDOPT(ForceDwarfFrameSection);
 
+  static cl::opt<bool> XRayOmitFunctionIndex(
+      "no-xray-index", cl::desc("Don't emit xray_fn_idx section"),
+      cl::init(false));
+  CGBINDOPT(XRayOmitFunctionIndex);
+
 #undef CGBINDOPT
 
   mc::RegisterMCTargetOptionsFlags();
@@ -470,6 +476,7 @@ TargetOptions codegen::InitTargetOptionsFromCodeGenFlags() {
   Options.EmitCallSiteInfo = getEmitCallSiteInfo();
   Options.EnableDebugEntryValues = getEnableDebugEntryValues();
   Options.ForceDwarfFrameSection = getForceDwarfFrameSection();
+  Options.XRayOmitFunctionIndex = getXRayOmitFunctionIndex();
 
   Options.MCOptions = mc::InitMCTargetOptionsFromFlags();