[XRay] Add -fxray-default-options to pass build-time defined XRay options

clang/include/clang/Basic/CodeGenOptions.h

@@ -399,6 +399,10 @@ class CodeGenOptions : public CodeGenOptionsBase {
   /// Set of XRay instrumentation kinds to emit.
   XRayInstrSet XRayInstrumentationBundle;
 
+  /// Default XRay options. Will be overrided by the XRAY_OPTIONS
+  /// environment variable during run-time.
+  std::string XRayDefaultOptions;
+
   std::vector<std::string> DefaultFunctionAttrs;
 
   /// List of dynamic shared object files to be loaded as pass plugins.

clang/include/clang/Driver/Options.td

@@ -2882,6 +2882,12 @@ defm xray_instrument : BoolFOption<"xray-instrument",
           "Generate XRay instrumentation sleds on function entry and exit">,
   NegFlag<SetFalse>>;
 
+def fxray_default_options_EQ :
+  Joined<["-"], "fxray-default-options=">,
+  Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Default XRay options. Can be overwritten by XRAY_OPTIONS environment variable during run-time.">,
+  MarshallingInfoString<CodeGenOpts<"XRayDefaultOptions">>;
+
 def fxray_instruction_threshold_EQ :
   Joined<["-"], "fxray-instruction-threshold=">,
   Group<f_Group>, Visibility<[ClangOption, CC1Option]>,

clang/lib/CodeGen/BackendUtil.cpp

@@ -77,6 +77,7 @@
 #include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h"
 #include "llvm/Transforms/Instrumentation/SanitizerCoverage.h"
 #include "llvm/Transforms/Instrumentation/ThreadSanitizer.h"
+#include "llvm/Transforms/Instrumentation/XRayPreparation.h"
 #include "llvm/Transforms/ObjCARC.h"
 #include "llvm/Transforms/Scalar/EarlyCSE.h"
 #include "llvm/Transforms/Scalar/GVN.h"
@@ -1062,6 +1063,12 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
       });
     }
 
+    if (!CodeGenOpts.XRayDefaultOptions.empty()) {
+      PB.registerOptimizerLastEPCallback(
+          [](ModulePassManager &MPM, OptimizationLevel Level,
+             ThinOrFullLTOPhase) { MPM.addPass(XRayPreparationPass()); });
+    }
+
     if (CodeGenOpts.FatLTO) {
       MPM.addPass(PB.buildFatLTODefaultPipeline(
           Level, PrepareForThinLTO,

clang/lib/CodeGen/CodeGenModule.cpp

@@ -448,6 +448,14 @@ CodeGenModule::CodeGenModule(ASTContext &C,
   if (Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
     getModule().addModuleFlag(llvm::Module::Error, "NumRegisterParameters",
                               CodeGenOpts.NumRegisterParameters);
+
+  // Insert XRay default options if it hasn't been done.
+  if (CodeGenOpts.XRayInstrumentFunctions &&
+      !CodeGenOpts.XRayDefaultOptions.empty() &&
+      !getModule().getModuleFlag("xray-default-opts"))
+    getModule().addModuleFlag(
+        llvm::Module::Error, "xray-default-opts",
+        llvm::MDString::get(LLVMContext, CodeGenOpts.XRayDefaultOptions));
 }
 
 CodeGenModule::~CodeGenModule() {}

clang/lib/Driver/XRayArgs.cpp

@@ -200,6 +200,9 @@ void XRayArgs::addArgs(const ToolChain &TC, const ArgList &Args,
     Args.addOptInFlag(CmdArgs, options::OPT_fxray_shared,
                       options::OPT_fno_xray_shared);
 
+  if (const Arg *A = Args.getLastArg(options::OPT_fxray_default_options_EQ))
+    A->render(Args, CmdArgs);
+
   if (const Arg *A =
           Args.getLastArg(options::OPT_fxray_instruction_threshold_EQ)) {
     int Value;

clang/test/CodeGen/xray-default-options.c

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -fxray-instrument -fxray-default-options='patch_premain=true,xray_mode=xray-basic' \
+// RUN:     -std=c11 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
+
+void justAFunction() {
+}
+
+// CHECK: !{{[0-9]+}} = !{i32 1, !"xray-default-opts", !"patch_premain=true,xray_mode=xray-basic"}

compiler-rt/lib/xray/CMakeLists.txt

@@ -7,6 +7,7 @@ set(XRAY_SOURCES
   xray_flags.cpp
   xray_interface.cpp
   xray_log_interface.cpp
+  xray_options_var.cpp
   xray_utils.cpp
   )
 

compiler-rt/lib/xray/xray_flags.cpp

@@ -67,6 +67,10 @@ void initializeFlags() XRAY_NEVER_INSTRUMENT {
   const char *XRayCompileFlags = useCompilerDefinedFlags();
   XRayParser.ParseString(XRayCompileFlags);
 
+  // Override from compile-time options.
+  if (XRAY_OPTIONS_VAR[0] != 0)
+    XRayParser.ParseString(XRAY_OPTIONS_VAR);
+
   // Override from environment variables.
   XRayParser.ParseStringFromEnv("XRAY_OPTIONS");
 

compiler-rt/lib/xray/xray_flags.h

@@ -17,6 +17,12 @@
 #include "sanitizer_common/sanitizer_flag_parser.h"
 #include "sanitizer_common/sanitizer_internal_defs.h"
 
+#define XRAY_OPTIONS_VAR __llvm_xray_options
+
+extern "C" {
+extern char XRAY_OPTIONS_VAR[1];
+}
+
 namespace __xray {
 
 struct Flags {

compiler-rt/lib/xray/xray_options_var.cpp

@@ -0,0 +1,24 @@
+/*===----- xray_options_var.cpp - XRay option variable setup  -------------===*\
+|*
+|* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+|* See https://llvm.org/LICENSE.txt for license information.
+|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+|*
+\*===----------------------------------------------------------------------===*/
+
+#include "xray_flags.h"
+
+// FIXME: Generalize these. See lib/profile/InstrProfilingPort.h and
+// include/profile/InstrProfData.inc
+#define COMPILER_RT_VISIBILITY __attribute__((visibility("hidden")))
+#define COMPILER_RT_WEAK __attribute__((weak))
+
+extern "C" {
+/* char __llvm_xray_options[1]
+ *
+ * The runtime should only provide its own definition of this symbol when the
+ * user has not specified one. Set this up by moving the runtime's copy of this
+ * symbol to an object file within the archive.
+ */
+COMPILER_RT_WEAK COMPILER_RT_VISIBILITY char XRAY_OPTIONS_VAR[1] = {0};
+}

compiler-rt/test/xray/TestCases/Posix/default-options.cpp

@@ -0,0 +1,12 @@
+// RUN: %clang_xray -g -fxray-default-options='patch_premain=true:verbosity=1:xray_mode=xray-basic' -o %t %s
+// RUN: rm -f xray-log.default-options.*
+// RUN: %run %t 2>&1 | FileCheck %s
+// RUN: rm -f xray-log.default-options.*
+//
+// REQUIRES: target={{(aarch64|loongarch64|x86_64)-.*}}
+// REQUIRES: built-in-llvm-tree
+__attribute__((xray_always_instrument)) void always() {}
+
+int main() { always(); }
+
+// CHECK: =={{[0-9].*}}==XRay: Log file in '{{.*}}'

llvm/docs/XRay.rst

@@ -157,7 +157,8 @@ Also by default the filename of the XRay trace is ``xray-log.XXXXXX`` where the
 ``XXXXXX`` part is randomly generated.
 
 These options can be controlled through the ``XRAY_OPTIONS`` environment
-variable, where we list down the options and their defaults below.
+variable during program run-time, where we list down the options and their
+defaults below.
 
 +-------------------+-----------------+---------------+------------------------+
 | Option            | Type            | Default       | Description            |
@@ -177,6 +178,18 @@ variable, where we list down the options and their defaults below.
 |                   |                 |               | level.                 |
 +-------------------+-----------------+---------------+------------------------+
 
+In addition to environment variable, you can also use ``-fxray-default-options``
+to specify default XRay options during program build time.
+
+For example, programs built with the following flags automatically use
+'patch_premain=true,xray_mode=basic' by default even without setting ``XRAY_OPTIONS``.
+
+::
+
+  clang -fxray-instrument -fxray-default-options='patch_premain=true,xray_mode=basic' ...
+
+Note that you still can override options designated by ``-fxray-default-options``
+using ``XRAY_OPTIONS`` during run-time.
 
 If you choose to not use the default logging implementation that comes with the
 XRay runtime and/or control when/how the XRay instrumentation runs, you may use

llvm/include/llvm/Transforms/Instrumentation/XRayPreparation.h

@@ -0,0 +1,24 @@
+//===- XRayPreparation.h - Preparation for XRay instrumentation -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This Pass does some IR-level preparations (e.g. inserting global variable
+// that carries default options, if there is any) for XRay instrumentation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_INSTRUMENTATION_XRAYPREPARATION_H
+#define LLVM_TRANSFORMS_INSTRUMENTATION_XRAYPREPARATION_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+struct XRayPreparationPass : public PassInfoMixin<XRayPreparationPass> {
+  PreservedAnalyses run(Module &, ModuleAnalysisManager &);
+};
+} // namespace llvm
+#endif

llvm/lib/Passes/PassBuilder.cpp

@@ -221,6 +221,7 @@
 #include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h"
 #include "llvm/Transforms/Instrumentation/SanitizerCoverage.h"
 #include "llvm/Transforms/Instrumentation/ThreadSanitizer.h"
+#include "llvm/Transforms/Instrumentation/XRayPreparation.h"
 #include "llvm/Transforms/ObjCARC.h"
 #include "llvm/Transforms/Scalar/ADCE.h"
 #include "llvm/Transforms/Scalar/AlignmentFromAssumptions.h"

llvm/lib/Passes/PassRegistry.def

@@ -157,6 +157,7 @@ MODULE_PASS("tsan-module", ModuleThreadSanitizerPass())
 MODULE_PASS("verify", VerifierPass())
 MODULE_PASS("view-callgraph", CallGraphViewerPass())
 MODULE_PASS("wholeprogramdevirt", WholeProgramDevirtPass())
+MODULE_PASS("xray-preparation", XRayPreparationPass())
 #undef MODULE_PASS
 
 #ifndef MODULE_PASS_WITH_PARAMS

llvm/lib/Transforms/Instrumentation/CMakeLists.txt

@@ -26,6 +26,7 @@ add_llvm_component_library(LLVMInstrumentation
   ThreadSanitizer.cpp
   HWAddressSanitizer.cpp
   RealtimeSanitizer.cpp
+  XRayPreparation.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Transforms

llvm/lib/Transforms/Instrumentation/XRayPreparation.cpp

@@ -0,0 +1,49 @@
+//===- XRayPreparation.cpp - Preparation for XRay instrumentation -------- ===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This Pass does some IR-level preparations (e.g. inserting global variable
+// that carries default options, if there is any) for XRay instrumentation.
+//
+//===---------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Instrumentation/XRayPreparation.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Module.h"
+#include "llvm/TargetParser/Triple.h"
+
+using namespace llvm;
+
+static void createXRayDefaultOptionsVar(Module &M, StringRef DefaultOptions) {
+  Constant *DefaultOptionsConst =
+      ConstantDataArray::getString(M.getContext(), DefaultOptions, true);
+  // This global variable will be passed into XRay's compiler-rt and used as
+  // the initial set of XRay options.
+  GlobalVariable *DefaultOptsVar = new GlobalVariable(
+      M, DefaultOptionsConst->getType(), true, GlobalValue::WeakAnyLinkage,
+      DefaultOptionsConst, "__llvm_xray_options");
+  DefaultOptsVar->setVisibility(GlobalValue::HiddenVisibility);
+  Triple TT(M.getTargetTriple());
+  if (TT.supportsCOMDAT()) {
+    DefaultOptsVar->setLinkage(GlobalValue::ExternalLinkage);
+    DefaultOptsVar->setComdat(M.getOrInsertComdat("__llvm_xray_options"));
+  }
+}
+
+PreservedAnalyses XRayPreparationPass::run(Module &M,
+                                           ModuleAnalysisManager &MAM) {
+  // XRay default options.
+  if (const auto *DefaultOpts =
+          dyn_cast_or_null<MDString>(M.getModuleFlag("xray-default-opts"))) {
+    createXRayDefaultOptionsVar(M, DefaultOpts->getString());
+    PreservedAnalyses PA;
+    PA.preserveSet<CFGAnalyses>();
+    return PA;
+  }
+
+  return PreservedAnalyses::all();
+}

llvm/test/CodeGen/X86/xray-default-options.ll

@@ -0,0 +1,10 @@
+; RUN: opt -S -p xray-preparation < %s | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: $__llvm_xray_options = comdat any
+; CHECK: @__llvm_xray_options = hidden constant [40 x i8] c"patch_premain=true,xray_mode=xray-basic\00", comdat
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"xray-default-opts", !"patch_premain=true,xray_mode=xray-basic"}