[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, 24 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 89ee7fc74c3..035165cdb9e 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1489,6 +1489,30 @@ bool CodeGenModule::isInSanitizerBlacklist(llvm::GlobalVariable *GV,
   return false;
 }
 
+bool CodeGenModule::imbueXRayAttrs(llvm::Function *Fn, SourceLocation Loc,
+                                   StringRef Category) const {
+  if (!LangOpts.XRayInstrument)
+    return false;
+  const auto &XRayFilter = getContext().getXRayFilter();
+  using ImbueAttr = XRayFunctionFilter::ImbueAttribute;
+  auto Attr = XRayFunctionFilter::ImbueAttribute::NONE;
+  if (Loc.isValid())
+    Attr = XRayFilter.shouldImbueLocation(Loc, Category);
+  if (Attr == ImbueAttr::NONE)
+    Attr = XRayFilter.shouldImbueFunction(Fn->getName());
+  switch (Attr) {
+  case ImbueAttr::NONE:
+    return false;
+  case ImbueAttr::ALWAYS:
+    Fn->addFnAttr("function-instrument", "xray-always");
+    break;
+  case ImbueAttr::NEVER:
+    Fn->addFnAttr("function-instrument", "xray-never");
+    break;
+  }
+  return true;
+}
+
 bool CodeGenModule::MustBeEmitted(const ValueDecl *Global) {
   // Never defer when EmitAllDecls is specified.
   if (LangOpts.EmitAllDecls)