Add XRay flags to Clang. We implement two flags to control the XRay behaviour:

-fxray-instrument: enables XRay annotation of IR
-fxray-instruction-threshold: configures the threshold for function size (looking at IR instructions), and allow LLVM to decide whether to add the nop sleds later on in the process.

Also implements the related xray_always_instrument and xray_never_instrument function attributes.

Patch by Dean Michael Berris.

llvm-svn: 275330

1 files changed, 20 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 755881fb148..183ee12ea23 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -397,6 +397,12 @@ bool CodeGenFunction::ShouldInstrumentFunction() {
   return true;
 }
 
+/// ShouldXRayInstrument - Return true if the current function should be
+/// instrumented with XRay nop sleds.
+bool CodeGenFunction::ShouldXRayInstrumentFunction() const {
+  return CGM.getCodeGenOpts().XRayInstrumentFunctions;
+}
+
 /// EmitFunctionInstrumentation - Emit LLVM code to call the specified
 /// instrumentation function with the current function and the call site, if
 /// function instrumentation is enabled.
@@ -686,6 +692,20 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
   if (SanOpts.has(SanitizerKind::SafeStack))
     Fn->addFnAttr(llvm::Attribute::SafeStack);
 
+  // Apply xray attributes to the function (as a string, for now)
+  if (D && ShouldXRayInstrumentFunction()) {
+    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");
+    } else {
+      Fn->addFnAttr(
+          "xray-instruction-threshold",
+          llvm::itostr(CGM.getCodeGenOpts().XRayInstructionThreshold));
+    }
+  }
+
   // Pass inline keyword to optimizer if it appears explicitly on any
   // declaration. Also, in the case of -fno-inline attach NoInline
   // attribute to all functions that are not marked AlwaysInline, or