[Driver][SYCL] Add support for -ftarget-compile-fast (#8995)

Adds support for -ftarget-compile-fast, which is used with offloading
target compilations for spir64_gen. This enables additional igc options
which can improve compile time. For JIT, use of environment variables is
needed as option passing does not look to be supported at this time.

Author: mdtoguchi

clang/include/clang/Driver/Options.td

@@ -3087,6 +3087,9 @@ def fsycl_max_parallel_jobs_EQ : Joined<["-"], "fsycl-max-parallel-link-jobs=">,
   HelpText<"Experimental feature: Controls the maximum parallelism of actions performed "
   "on SYCL device code post-link, i.e. the generation of SPIR-V device images "
   "or AOT compilation of each device image.">;
+def ftarget_compile_fast : Flag<["-"], "ftarget-compile-fast">,
+  Flags<[CoreOption]>, HelpText<"Experimental feature: Reduce target "
+  "compilation time, with potential runtime performance trade-off.">;
 def : Flag<["-"], "fsycl-rdc">, Flags<[CoreOption]>, Alias<fgpu_rdc>;
 def : Flag<["-"], "fno-sycl-rdc">, Flags<[CoreOption]>, Alias<fno_gpu_rdc>;
 def fsycl_optimize_non_user_code : Flag<["-"], "fsycl-optimize-non-user-code">,

clang/lib/Driver/ToolChains/SYCL.cpp

@@ -977,6 +977,11 @@ void SYCLToolChain::AddImpliedTargetArgs(const llvm::Triple &Triple,
       CmdArgs.push_back("-device");
       CmdArgs.push_back(Args.MakeArgString(DepInfo));
     }
+    // -ftarget-compile-fast
+    if (Args.hasArg(options::OPT_ftarget_compile_fast)) {
+      BeArgs.push_back(
+          "\"-igc_opts PartitionUnit=1,SubroutineThreshold=50000\"");
+    }
   }
   if (BeArgs.empty())
     return;

clang/test/Driver/ftarget-compile-fast.cpp

@@ -0,0 +1,11 @@
+// Test -ftarget-compile-fast behaviors
+
+// RUN: %clang -### -target x86_64-unknown-linux-gnu -fsycl \
+// RUN:    -fsycl-targets=spir64_gen -ftarget-compile-fast %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=TARGET_COMPILE_FAST_GEN %s
+// RUN: %clang_cl -### --target=x86_64-pc-windows-msvc -fsycl \
+// RUN:     -fsycl-targets=spir64_gen -ftarget-compile-fast %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=TARGET_COMPILE_FAST_GEN %s
+
+// TARGET_COMPILE_FAST_GEN: ocloc{{.*}} "-output"
+// TARGET_COMPILE_FAST_GEN: "-options" "{{.*}}-igc_opts PartitionUnit=1,SubroutineThreshold=50000{{.*}}"