[XRay][clang] Emit "never-instrument" attribute

Summary:
Before this change, we only emit the XRay attributes in LLVM IR when the
-fxray-instrument flag is provided. This may cause issues with thinlto
when the final binary is being built/linked with -fxray-instrument, and
the constitutent LLVM IR gets re-lowered with xray instrumentation.

With this change, we can honour the "never-instrument "attributes
provided in the source code and preserve those in the IR. This way, even
in thinlto builds, we retain the attributes which say whether functions
should never be XRay instrumented.

This change addresses llvm.org/PR38922.

Reviewers: mboerger, eizan

Subscribers: mehdi_amini, dexonsmith, cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D52015

llvm-svn: 342200

1 files changed, 12 insertions, 12 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index d14275531cd..77f978f687e 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -901,21 +901,21 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
   }
 
   // Apply xray attributes to the function (as a string, for now)
-  bool InstrumentXray = ShouldXRayInstrumentFunction() &&
-                        CGM.getCodeGenOpts().XRayInstrumentationBundle.has(
-                            XRayInstrKind::Function);
-  if (D && InstrumentXray) {
+  if (D) {
     if (const auto *XRayAttr = D->getAttr<XRayInstrumentAttr>()) {
-      if (XRayAttr->alwaysXRayInstrument())
-        Fn->addFnAttr("function-instrument", "xray-always");
-      if (XRayAttr->neverXRayInstrument())
-        Fn->addFnAttr("function-instrument", "xray-never");
-      if (const auto *LogArgs = D->getAttr<XRayLogArgsAttr>()) {
-        Fn->addFnAttr("xray-log-args",
-                      llvm::utostr(LogArgs->getArgumentCount()));
+      if (CGM.getCodeGenOpts().XRayInstrumentationBundle.has(
+              XRayInstrKind::Function)) {
+        if (XRayAttr->alwaysXRayInstrument() && ShouldXRayInstrumentFunction())
+          Fn->addFnAttr("function-instrument", "xray-always");
+        if (XRayAttr->neverXRayInstrument())
+          Fn->addFnAttr("function-instrument", "xray-never");
+        if (const auto *LogArgs = D->getAttr<XRayLogArgsAttr>())
+          if (ShouldXRayInstrumentFunction())
+            Fn->addFnAttr("xray-log-args",
+                          llvm::utostr(LogArgs->getArgumentCount()));
       }
     } else {
-      if (!CGM.imbueXRayAttrs(Fn, Loc))
+      if (ShouldXRayInstrumentFunction() && !CGM.imbueXRayAttrs(Fn, Loc))
         Fn->addFnAttr(
             "xray-instruction-threshold",
             llvm::itostr(CGM.getCodeGenOpts().XRayInstructionThreshold));