[SYCL] Remove redundant build options processing

After 86b0e8d patch extra operations with device images happen before
check if it is present in in-memory cache. For applications with small
kernels which are executed multiple times noticeable performance
degradation is seen for host code. That was done to get build options
stored in the kernel image and use them as in-memory cache key. At the
same time kernel image (where these options are taken from) is used in
cache key so it is reasonable to use only build options which are
specified in SYCL API and/or environment variables as separate cache
key.

Getting build options from kernel image is moved back to build
operation which happens only if built program is missed in in-memory
cache.

Author: vladimirlaz

sycl/source/detail/program_manager/program_manager.cpp

@@ -367,35 +367,50 @@ RT::PiProgram ProgramManager::getBuiltPIProgram(OSModuleHandle M,
   auto GetF = [](const Locked<ProgramCacheT> &LockedCache) -> ProgramCacheT & {
     return LockedCache.get();
   };
-  std::string BuildOptions;
-  if (Prg)
-    BuildOptions = Prg->get_build_options();
-  const RTDeviceBinaryImage &Img =
-      getDeviceImage(M, KSId, Context, Device, JITCompilationIsRequired);
-  std::string CompileOpts = Img.getCompileOptions();
-  std::string LinkOpts = Img.getLinkOptions();
-  pi_device_binary_property isEsimdImage = Img.getProperty("isEsimdImage");
-  if (!BuildOptions.empty()) {
-    CompileOpts += " ";
-    CompileOpts += BuildOptions;
-  }
-  if (isEsimdImage && pi::DeviceBinaryProperty(isEsimdImage).asUint32()) {
-    if (!CompileOpts.empty())
-      CompileOpts += " ";
-    CompileOpts += "-vc-codegen";
-  }
 
-  // Build options are overridden if environment variables are present
-  const char *CompileOptsEnv = SYCLConfig<SYCL_PROGRAM_COMPILE_OPTIONS>::get();
+  std::string CompileOpts;
+  std::string LinkOpts;
+  // Build options are overridden if environment variables are present.
+  // Environment variables are not changed during program lifecycle so it
+  // is reasonable to use static here to read them only once.
+  static const char *CompileOptsEnv =
+      SYCLConfig<SYCL_PROGRAM_COMPILE_OPTIONS>::get();
   if (CompileOptsEnv) {
     CompileOpts = CompileOptsEnv;
+  } else { // Use build options only when the environment variable is missed
+    if (Prg) {
+      std::string BuildOptions = Prg->get_build_options();
+      if (!BuildOptions.empty()) {
+        CompileOpts += " ";
+        CompileOpts += BuildOptions;
+      }
+    }
   }
-  const char *LinkOptsEnv = SYCLConfig<SYCL_PROGRAM_LINK_OPTIONS>::get();
+  static const char *LinkOptsEnv = SYCLConfig<SYCL_PROGRAM_LINK_OPTIONS>::get();
   if (LinkOptsEnv) {
     LinkOpts = LinkOptsEnv;
   }
 
-  auto BuildF = [this, &Context, &Device, Prg, &Img, &CompileOpts, &LinkOpts] {
+  auto BuildF = [this, &M, &KSId, &Context, &Device, Prg, &CompileOpts,
+                 &LinkOpts, &JITCompilationIsRequired] {
+    const RTDeviceBinaryImage &Img =
+        getDeviceImage(M, KSId, Context, Device, JITCompilationIsRequired);
+    // Update only if compile options are not overwritten by environment
+    // variable
+    if (!CompileOptsEnv) {
+      CompileOpts += Img.getCompileOptions();
+      pi_device_binary_property isEsimdImage = Img.getProperty("isEsimdImage");
+
+      if (isEsimdImage && pi::DeviceBinaryProperty(isEsimdImage).asUint32()) {
+        if (!CompileOpts.empty())
+          CompileOpts += " ";
+        CompileOpts += "-vc-codegen";
+      }
+    }
+
+    // Update only if link options are not overwritten by environment variable
+    if (!LinkOptsEnv)
+      LinkOpts += Img.getLinkOptions();
     ContextImplPtr ContextImpl = getSyclObjImpl(Context);
     const detail::plugin &Plugin = ContextImpl->getPlugin();
     RT::PiProgram NativePrg = createPIProgram(Img, Context, Device);
@@ -820,14 +835,6 @@ ProgramManager::ProgramPtr ProgramManager::build(
   }
 
   bool LinkDeviceLibs = (DeviceLibReqMask != 0);
-  const char *CompileOpts = std::getenv("SYCL_PROGRAM_COMPILE_OPTIONS");
-  if (!CompileOpts) {
-    CompileOpts = CompileOptions.c_str();
-  }
-  const char *LinkOpts = std::getenv("SYCL_PROGRAM_LINK_OPTIONS");
-  if (!LinkOpts) {
-    LinkOpts = LinkOptions.c_str();
-  }
 
   // TODO: Currently, online linking isn't implemented yet on Level Zero.
   // To enable device libraries and unify the behaviors on all backends,
@@ -839,9 +846,8 @@ ProgramManager::ProgramPtr ProgramManager::build(
   // TODO: this is a temporary workaround for GPU tests for ESIMD compiler.
   // We do not link with other device libraries, because it may fail
   // due to unrecognized SPIR-V format of those libraries.
-  if (std::string(CompileOpts).find(std::string("-cmc")) != std::string::npos ||
-      std::string(CompileOpts).find(std::string("-vc-codegen")) !=
-          std::string::npos)
+  if (CompileOptions.find(std::string("-cmc")) != std::string::npos ||
+      CompileOptions.find(std::string("-vc-codegen")) != std::string::npos)
     LinkDeviceLibs = false;
 
   std::vector<RT::PiProgram> LinkPrograms;
@@ -852,11 +858,9 @@ ProgramManager::ProgramPtr ProgramManager::build(
 
   const detail::plugin &Plugin = Context->getPlugin();
   if (LinkPrograms.empty()) {
-    std::string Opts(CompileOpts);
-
     RT::PiResult Error = Plugin.call_nocheck<PiApiKind::piProgramBuild>(
-        Program.get(), /*num devices =*/1, &Device, Opts.c_str(), nullptr,
-        nullptr);
+        Program.get(), /*num devices =*/1, &Device, CompileOptions.c_str(),
+        nullptr, nullptr);
     if (Error != PI_SUCCESS)
       throw compile_program_error(getProgramBuildLog(Program.get(), Context),
                                   Error);
@@ -865,13 +869,13 @@ ProgramManager::ProgramPtr ProgramManager::build(
 
   // Include the main program and compile/link everything together
   Plugin.call<PiApiKind::piProgramCompile>(Program.get(), /*num devices =*/1,
-                                           &Device, CompileOpts, 0, nullptr,
-                                           nullptr, nullptr, nullptr);
+                                           &Device, CompileOptions.c_str(), 0,
+                                           nullptr, nullptr, nullptr, nullptr);
   LinkPrograms.push_back(Program.get());
 
   RT::PiProgram LinkedProg = nullptr;
   RT::PiResult Error = Plugin.call_nocheck<PiApiKind::piProgramLink>(
-      Context->getHandleRef(), /*num devices =*/1, &Device, LinkOpts,
+      Context->getHandleRef(), /*num devices =*/1, &Device, LinkOptions.c_str(),
       LinkPrograms.size(), LinkPrograms.data(), nullptr, nullptr, &LinkedProg);
 
   // Link program call returns a new program object if all parameters are valid,