[XRay] Add __xray_customeevent(...) as a clang-supported builtin

Summary:
We define the `__xray_customeevent` builtin that gets translated to
IR calls to the correct intrinsic. The default implementation of this is
a no-op function. The codegen side of this follows the following logic:

- When `-fxray-instrument` is not provided in the driver, we elide all
calls to `__xray_customevent`.
- When `-fxray-instrument` is enabled and a function is marked as "never
instrumented", we elide all calls to `__xray_customevent` in that
function; if either marked as "always instrumented" or subject to
threshold-based instrumentation, we emit a call to the
`llvm.xray.customevent` intrinsic from LLVM for each
`__xray_customevent` occurrence in the function.

This change depends on D27503 (to land in LLVM first).

Reviewers: echristo, rsmith

Subscribers: mehdi_amini, pelikan, lrl, cfe-commits

Differential Revision: https://reviews.llvm.org/D30018

llvm-svn: 302492

1 files changed, 28 insertions, 0 deletions

diff --git a/clang/test/CodeGen/xray-customevent.cpp b/clang/test/CodeGen/xray-customevent.cpp
new file mode 100644
index 00000000000..359d92df938
--- /dev/null
+++ b/clang/test/CodeGen/xray-customevent.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -fxray-instrument -x c++ -std=c++11 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: @_Z16alwaysInstrumentv
+[[clang::xray_always_instrument]] void alwaysInstrument() {
+  static constexpr char kPhase[] = "instrument";
+  __xray_customevent(kPhase, 10);
+  // CHECK: call void @llvm.xray.customevent(i8*{{.*}}, i32 10)
+}
+
+// CHECK-LABEL: @_Z15neverInstrumentv
+[[clang::xray_never_instrument]] void neverInstrument() {
+  static constexpr char kPhase[] = "never";
+  __xray_customevent(kPhase, 5);
+  // CHECK-NOT: call void @llvm.xray.customevent(i8*{{.*}}, i32 5)
+}
+
+// CHECK-LABEL: @_Z21conditionalInstrumenti
+[[clang::xray_always_instrument]] void conditionalInstrument(int v) {
+  static constexpr char kTrue[] = "true";
+  static constexpr char kUntrue[] = "untrue";
+  if (v % 2)
+    __xray_customevent(kTrue, 4);
+  else
+    __xray_customevent(kUntrue, 6);
+
+  // CHECK: call void @llvm.xray.customevent(i8*{{.*}}, i32 4)
+  // CHECK: call void @llvm.xray.customevent(i8*{{.*}}, i32 6)
+}