[SYCL][PM] Fix DeadArgumentEliminationSYCLPass with new pass manager (#6074)

* [SYCL][PM] Fix DeadArgumentEliminationSYCLPass with new pass manager

* Add it properly to the PM, implementing in clang. It might be not the most "correct" way but it is consistent with other similar passes' location and any cleanups should be done all at once, not creating divergence between different passes.
* Add test to check pass run in optimized compilations
* Fix documentation, it's enabled by default long time ago

Co-authored-by: Andrei Elovikov <andrei.elovikov@intel.com>

Author: Pavel Chupin

clang/lib/CodeGen/BackendUtil.cpp

@@ -62,6 +62,7 @@
 #include "llvm/Transforms/Coroutines/CoroSplit.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/AlwaysInliner.h"
+#include "llvm/Transforms/IPO/DeadArgumentElimination.h"
 #include "llvm/Transforms/IPO/LowerTypeTests.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
 #include "llvm/Transforms/IPO/ThinLTOBitcodeWriter.h"
@@ -1490,6 +1491,8 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
   }
   if (LangOpts.SYCLIsDevice) {
     MPM.addPass(SYCLMutatePrintfAddrspacePass());
+    if (!CodeGenOpts.DisableLLVMPasses && LangOpts.EnableDAEInSpirKernels)
+      MPM.addPass(DeadArgumentEliminationSYCLPass());
   }
 
   // Add SPIRITTAnnotations pass to the pass manager if

clang/test/CodeGenSYCL/dead-elim-sycl.cpp

@@ -0,0 +1,13 @@
+// RUN: %clang -cc1 -triple spir64-unknown-unknown  -fsycl-is-device  -emit-llvm-bc  -O1 -fno-legacy-pass-manager -fdebug-pass-manager -fenable-sycl-dae -o /dev/null -x c++ < %s 2>&1 | FileCheck %s
+// RUN: %clang -cc1 -triple spir64-unknown-unknown  -fsycl-is-device  -emit-llvm-bc  -O0 -fno-legacy-pass-manager -fdebug-pass-manager  -o /dev/null -x c++ < %s 2>&1 | FileCheck %s --check-prefix DISABLE
+// RUN: %clang -cc1 -triple spir64-unknown-unknown  -fsycl-is-device  -emit-llvm-bc  -O1 -fno-legacy-pass-manager -fdebug-pass-manager -fenable-sycl-dae -disable-llvm-passes -o /dev/null -x c++ < %s 2>&1 | FileCheck %s --check-prefix DISABLE
+// RUN: %clang -cc1 -triple spir64-unknown-unknown  -fsycl-is-device  -emit-llvm-bc  -O1 -flegacy-pass-manager -mllvm -debug-pass=Structure -fenable-sycl-dae -o /dev/null -x c++ < %s 2>&1 | FileCheck %s --check-prefix OLDPM
+// RUN: %clang -cc1 -triple spir64-unknown-unknown  -fsycl-is-device  -emit-llvm-bc  -O1 -flegacy-pass-manager -mllvm -debug-pass=Structure -o /dev/null -x c++ < %s 2>&1 | FileCheck %s --check-prefix DISABLE
+// RUN: %clang -cc1 -triple spir64-unknown-unknown  -fsycl-is-device  -emit-llvm-bc  -O1 -flegacy-pass-manager -mllvm -debug-pass=Structure -fenable-sycl-dae -disable-llvm-passes -o /dev/null -x c++ < %s 2>&1 | FileCheck %s --check-prefix DISABLE
+
+// Verify that Dead Arguments Elimination for SYCL kernels is/is not added to the PM.
+
+// CHECK: Running pass: DeadArgumentEliminationSYCLPass on [module]
+// OLDPM: Dead Argument Elimination for SYCL kernels
+// DISABLE-NOT: DeadArgumentEliminationSYCLPass
+// DISABLE-NOT: Dead Argument Elimination for SYCL kernels

sycl/doc/UsersManual.md

@@ -70,7 +70,7 @@ and not recommended to use in production environment.
     Enables (or disables) LLVM IR dead argument elimination pass to remove
     unused arguments for the kernel functions before translation to SPIR-V.
     Currently has effect only on spir64\* targets.
-    Disabled by default.
+    Enabled by default.
 
 **`-f[no-]sycl-id-queries-fit-in-int`**