[DAE][SYCL] - Removed DAE from standard optimization pipeline

We cannot run DAE in ESIMD cntext since the pointers to SPIR kernel
functions are saved in !genx.kernels metadata. Because of that I
removed DAE pass from the standard pipeline and put it in the place
that is specific for SYCL passes and guarded it under a new
temporary option: '-fenable-sycl-dae'. This option is only used until
other parts of the solution are not in place.

Author: DenisBakhvalov

clang/include/clang/Basic/LangOptions.def

@@ -251,6 +251,7 @@ LANGOPT(SYCLUnnamedLambda , 1, 0, "Allow unnamed lambda SYCL kernels")
 LANGOPT(SYCLVersion       , 32, 0, "Version of the SYCL standard used")
 LANGOPT(DeclareSPIRVBuiltins, 1, 0, "Declare SPIR-V builtin functions")
 LANGOPT(SYCLExplicitSIMD  , 1, 0, "SYCL compilation with explicit SIMD extension")
+LANGOPT(EnableDAEInSpirKernels , 1, 0, "Enable Dead Argument Elimination in SPIR kernels")
 
 LANGOPT(HIPUseNewLaunchAPI, 1, 0, "Use new kernel launching API for HIP")
 

clang/include/clang/Driver/Options.td

@@ -4456,6 +4456,8 @@ def fsycl_allow_func_ptr : Flag<["-"], "fsycl-allow-func-ptr">,
 def fno_sycl_allow_func_ptr : Flag<["-"], "fno-sycl-allow-func-ptr">;
 def fsycl_enable_optimizations: Flag<["-"], "fsycl-enable-optimizations">,
   HelpText<"Experimental flag enabling standard optimization in the front-end.">;
+def fenable_sycl_dae : Flag<["-"], "fenable-sycl-dae">,
+  HelpText<"Enable Dead Argument Elimination in SPIR kernels">;
 
 } // let Flags = [CC1Option]
 

clang/lib/CodeGen/BackendUtil.cpp

@@ -918,6 +918,15 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
   if (LangOpts.SYCLIsDevice && CodeGenOpts.DisableLLVMPasses)
     PerModulePasses.add(createDeadCodeEliminationPass());
 
+  // Eliminate dead arguments from SPIR kernels in SYCL environment.
+  // 1. Run DAE when LLVM optimizations are applied as well.
+  // 2. We cannot run DAE for ESIMD since the pointers to SPIR kernel
+  //    functions are saved in !genx.kernels metadata.
+  // 3. DAE pass temporary guarded under option.
+  if (LangOpts.SYCLIsDevice && !CodeGenOpts.DisableLLVMPasses &&
+      !LangOpts.SYCLExplicitSIMD && LangOpts.EnableDAEInSpirKernels)
+    PerModulePasses.add(createDeadArgEliminationSYCLPass());
+
   if (LangOpts.SYCLIsDevice && LangOpts.SYCLExplicitSIMD)
     PerModulePasses.add(createGenXSPIRVWriterAdaptorPass());
 

clang/lib/Frontend/CompilerInvocation.cpp

@@ -2596,6 +2596,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
       }
     }
     Opts.SYCLExplicitSIMD = Args.hasArg(options::OPT_fsycl_esimd);
+    Opts.EnableDAEInSpirKernels = Args.hasArg(options::OPT_fenable_sycl_dae);
   }
 
   Opts.IncludeDefaultHeader = Args.hasArg(OPT_finclude_default_header);

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -680,7 +680,6 @@ void PassManagerBuilder::populateModulePassManager(
   if (RunInliner) {
     MPM.add(createGlobalOptimizerPass());
     MPM.add(createGlobalDCEPass());
-    MPM.add(createDeadArgEliminationSYCLPass());
   }
 
   // If we are planning to perform ThinLTO later, let's not bloat the code with

llvm/test/Other/opt-O2-pipeline.ll

@@ -193,7 +193,6 @@
 ; CHECK-NEXT:         Branch Probability Analysis
 ; CHECK-NEXT:         Block Frequency Analysis
 ; CHECK-NEXT:     Dead Global Elimination
-; CHECK-NEXT:     Dead Argument Elimination for SPIR kernels in SYCL environment
 ; CHECK-NEXT:     CallGraph Construction
 ; CHECK-NEXT:     Globals Alias Analysis
 ; CHECK-NEXT:     FunctionPass Manager

llvm/test/Other/opt-O3-pipeline-enable-matrix.ll

@@ -198,7 +198,6 @@
 ; CHECK-NEXT:         Branch Probability Analysis
 ; CHECK-NEXT:         Block Frequency Analysis
 ; CHECK-NEXT:     Dead Global Elimination
-; CHECK-NEXT:     Dead Argument Elimination for SPIR kernels in SYCL environment
 ; CHECK-NEXT:     CallGraph Construction
 ; CHECK-NEXT:     Globals Alias Analysis
 ; CHECK-NEXT:     FunctionPass Manager

llvm/test/Other/opt-O3-pipeline.ll

@@ -198,7 +198,6 @@
 ; CHECK-NEXT:         Branch Probability Analysis
 ; CHECK-NEXT:         Block Frequency Analysis
 ; CHECK-NEXT:     Dead Global Elimination
-; CHECK-NEXT:     Dead Argument Elimination for SPIR kernels in SYCL environment
 ; CHECK-NEXT:     CallGraph Construction
 ; CHECK-NEXT:     Globals Alias Analysis
 ; CHECK-NEXT:     FunctionPass Manager

llvm/test/Other/opt-Os-pipeline.ll

@@ -179,7 +179,6 @@
 ; CHECK-NEXT:         Branch Probability Analysis
 ; CHECK-NEXT:         Block Frequency Analysis
 ; CHECK-NEXT:     Dead Global Elimination
-; CHECK-NEXT:     Dead Argument Elimination for SPIR kernels in SYCL environment
 ; CHECK-NEXT:     CallGraph Construction
 ; CHECK-NEXT:     Globals Alias Analysis
 ; CHECK-NEXT:     FunctionPass Manager