commit 05cf44346346c0308396cf59b2c7228b2b3eff30
author Dean Michael Berris <dberris@google.com> Fri Sep 14 01:59:12 2018 +0000
committer Dean Michael Berris <dberris@google.com> Fri Sep 14 01:59:12 2018 +0000
tree 03785a62a5b8f17802bc37c9d380250cb3b903e9
parent d8673901ab8fe5c104196d08b5c44da026f20870

[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

clang/lib/CodeGen/CodeGenFunction.cpp

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index d142755..77f978f 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -901,21 +901,21 @@
   }
 
   // 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));