[XRay] Add -fxray-{always,never}-instrument= flags to clang

Summary:
The -fxray-always-instrument= and -fxray-never-instrument= flags take
filenames that are used to imbue the XRay instrumentation attributes
using a whitelist mechanism (similar to the sanitizer special cases
list). We use the same syntax and semantics as the sanitizer blacklists
files in the implementation.

As implemented, we respect the attributes that are already defined in
the source file (i.e. those that have the
[[clang::xray_{always,never}_instrument]] attributes) before applying
the always/never instrument lists.

Reviewers: rsmith, chandlerc

Subscribers: jfb, mgorny, cfe-commits

Differential Revision: https://reviews.llvm.org/D30388

llvm-svn: 299041

1 files changed, 4 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 11660b4f419..79c0694f902 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -786,9 +786,10 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
                       llvm::utostr(LogArgs->getArgumentCount()));
       }
     } else {
-      Fn->addFnAttr(
-          "xray-instruction-threshold",
-          llvm::itostr(CGM.getCodeGenOpts().XRayInstructionThreshold));
+      if (!CGM.imbueXRayAttrs(Fn, Loc))
+        Fn->addFnAttr(
+            "xray-instruction-threshold",
+            llvm::itostr(CGM.getCodeGenOpts().XRayInstructionThreshold));
     }
   }