[SYCL] Enable parallel execution of llvm-foreach commands under an option

This improvement should speed up toolchain execution by launching underlying
llvm-foreach commands in parallel.
The feature can be enabled by passing '--parallel-exec' to the command line of
llvm-foreach.

Author: vmaksimo

llvm/test/tools/llvm-foreach/llvm-foreach-lin.ll

@@ -6,13 +6,17 @@
 ; RUN: echo "%t2.tgt" >> %t.list
 ; RUN: llvm-foreach --in-replace="{}" --in-file-list=%t.list -- echo "{}" > %t.res
 ; RUN: FileCheck < %t.res %s
-; CHECK: [[FIRST:.+1.tgt]]
-; CHECK: [[SECOND:.+2.tgt]]
+; RUN: llvm-foreach --parallel-exec --in-replace="{}" --in-file-list=%t.list -- echo "{}" > %t.res
+; RUN: FileCheck < %t.res %s
+; CHECK-DAG: [[FIRST:.+1.tgt]]
+; CHECK-DAG: [[SECOND:.+2.tgt]]
 ;
 ; RUN: llvm-foreach --in-replace="{}" --out-replace=%t --out-ext=out --in-file-list=%t.list --out-file-list=%t.out.list -- cp "{}" %t
 ; RUN: FileCheck < %t.out.list %s --check-prefix=CHECK-LIST
-; CHECK-LIST: [[FIRST:.+\.out]]
-; CHECK-LIST: [[SECOND:.+\.out]]
+; RUN: llvm-foreach --parallel-exec --in-replace="{}" --out-replace=%t --out-ext=out --in-file-list=%t.list --out-file-list=%t.out.list -- cp "{}" %t
+; RUN: FileCheck < %t.out.list %s --check-prefix=CHECK-LIST
+; CHECK-LIST-DAG: [[FIRST:.+\.out]]
+; CHECK-LIST-DAG: [[SECOND:.+\.out]]
 ; RUN: llvm-foreach --in-replace="{}" --in-file-list=%t.out.list -- FileCheck --input-file="{}" %s --check-prefix=CHECK-CONTENT
 ; CHECK-CONTENT: Content of
 
@@ -22,5 +26,7 @@
 ; RUN: echo "%t4.tgt" >> %t1.list
 ; RUN: llvm-foreach --in-replace="{}" --in-replace="inrep" --in-file-list=%t.list --in-file-list=%t1.list --out-increment="%t_out.prj" -- echo -first-part-of-arg={}.out -first-part-of-arg=inrep.out -another-arg=%t_out.prj > %t1.res
 ; RUN: FileCheck < %t1.res %s --check-prefix=CHECK-DOUBLE-LISTS
-; CHECK-DOUBLE-LISTS: -first-part-of-arg=[[FIRST:.+1.tgt.out]] -first-part-of-arg=[[THIRD:.+3.tgt.out]] -another-arg={{.+}}_out.prj
-; CHECK-DOUBLE-LISTS: -first-part-of-arg=[[SECOND:.+2.tgt.out]] -first-part-of-arg=[[FOURTH:.+4.tgt.out]] -another-arg={{.+}}_out.prj_1
+; RUN: llvm-foreach --parallel-exec --in-replace="{}" --in-replace="inrep" --in-file-list=%t.list --in-file-list=%t1.list --out-increment="%t_out.prj" -- echo -first-part-of-arg={}.out -first-part-of-arg=inrep.out -another-arg=%t_out.prj > %t1.res
+; RUN: FileCheck < %t1.res %s --check-prefix=CHECK-DOUBLE-LISTS
+; CHECK-DOUBLE-LISTS-DAG: -first-part-of-arg=[[FIRST:.+1.tgt.out]] -first-part-of-arg=[[THIRD:.+3.tgt.out]] -another-arg={{.+}}_out.prj
+; CHECK-DOUBLE-LISTS-DAG: -first-part-of-arg=[[SECOND:.+2.tgt.out]] -first-part-of-arg=[[FOURTH:.+4.tgt.out]] -another-arg={{.+}}_out.prj_1

llvm/test/tools/llvm-foreach/llvm-foreach-win.ll

@@ -6,13 +6,17 @@
 ; RUN: echo "%t2.tgt" >> %t.list
 ; RUN: llvm-foreach --in-replace="{}" --in-file-list=%t.list -- echo "{}" > %t.res
 ; RUN: FileCheck < %t.res %s
-; CHECK: [[FIRST:.+1.tgt]]
-; CHECK: [[SECOND:.+2.tgt]]
+; RUN: llvm-foreach --parallel-exec --in-replace="{}" --in-file-list=%t.list -- echo "{}" > %t.res
+; RUN: FileCheck < %t.res %s
+; CHECK-DAG: [[FIRST:.+1.tgt]]
+; CHECK-DAG: [[SECOND:.+2.tgt]]
 ;
 ; RUN: llvm-foreach --in-replace="{}" --out-replace=%t --out-ext=out --in-file-list=%t.list --out-file-list=%t.out.list -- xcopy /y "{}" %t
 ; RUN: FileCheck < %t.out.list %s --check-prefix=CHECK-LIST
-; CHECK-LIST: [[FIRST:.+\.out]]
-; CHECK-LIST: [[SECOND:.+\.out]]
+; RUN: llvm-foreach --parallel-exec --in-replace="{}" --out-replace=%t --out-ext=out --in-file-list=%t.list --out-file-list=%t.out.list -- xcopy /y "{}" %t
+; RUN: FileCheck < %t.out.list %s --check-prefix=CHECK-LIST
+; CHECK-LIST-DAG: [[FIRST:.+\.out]]
+; CHECK-LIST-DAG: [[SECOND:.+\.out]]
 ; RUN: llvm-foreach --in-replace="{}" --in-file-list=%t.out.list -- FileCheck --input-file="{}" %s --check-prefix=CHECK-CONTENT
 ; CHECK-CONTENT: Content of
 
@@ -22,5 +26,7 @@
 ; RUN: echo "%t4.tgt" >> %t1.list
 ; RUN: llvm-foreach --in-replace="{}" --in-replace="inrep" --in-file-list=%t.list --in-file-list=%t1.list --out-increment=%t_out.prj -- echo -first-part-of-arg={}.out -first-part-of-arg=inrep.out -another-arg=%t_out.prj > %t1.res
 ; RUN: FileCheck < %t1.res %s --check-prefix=CHECK-DOUBLE-LISTS
-; CHECK-DOUBLE-LISTS: -first-part-of-arg=[[FIRST:.+1.tgt.out]] -first-part-of-arg=[[THIRD:.+3.tgt.out]] -another-arg={{.+}}_out.prj
-; CHECK-DOUBLE-LISTS: -first-part-of-arg=[[SECOND:.+2.tgt.out]] -first-part-of-arg=[[FOURTH:.+4.tgt.out]] -another-arg={{.+}}_out.prj_1
+; RUN: llvm-foreach --parallel-exec --in-replace="{}" --in-replace="inrep" --in-file-list=%t.list --in-file-list=%t1.list --out-increment=%t_out.prj -- echo -first-part-of-arg={}.out -first-part-of-arg=inrep.out -another-arg=%t_out.prj > %t1.res
+; RUN: FileCheck < %t1.res %s --check-prefix=CHECK-DOUBLE-LISTS
+; CHECK-DOUBLE-LISTS-DAG: -first-part-of-arg=[[FIRST:.+1.tgt.out]] -first-part-of-arg=[[THIRD:.+3.tgt.out]] -another-arg={{.+}}_out.prj
+; CHECK-DOUBLE-LISTS-DAG: -first-part-of-arg=[[SECOND:.+2.tgt.out]] -first-part-of-arg=[[FOURTH:.+4.tgt.out]] -another-arg={{.+}}_out.prj_1

llvm/tools/llvm-foreach/llvm-foreach.cpp

@@ -19,6 +19,7 @@
 #include "llvm/Support/Program.h"
 #include "llvm/Support/SystemUtils.h"
 
+#include <list>
 #include <vector>
 
 using namespace llvm;
@@ -69,6 +70,11 @@ static cl::opt<std::string> OutIncrement{
         "pass."),
     cl::init(""), cl::value_desc("R")};
 
+static cl::opt<bool> ExecuteInParallel{
+    "parallel-exec",
+    cl::desc("Enable launching input commands in parallel mode"),
+    cl::init(false)};
+
 static void error(const Twine &Msg) {
   errs() << "llvm-foreach: " << Msg << '\n';
   exit(1);
@@ -170,6 +176,7 @@ int main(int argc, char **argv) {
   std::string IncOutArg;
   std::vector<std::string> ResInArgs(InReplaceArgs.size());
   std::string ResFileList = "";
+  std::list<sys::ProcessInfo> CommandsStarted;
   for (size_t j = 0; j != FileLists[0].size(); ++j) {
     for (size_t i = 0; i < InReplaceArgs.size(); ++i) {
       ArgumentReplace CurReplace = InReplaceArgs[i];
@@ -222,7 +229,12 @@ int main(int argc, char **argv) {
     }
 
     std::string ErrMsg;
-    // TODO: Add possibility to execute commands in parallel.
+    if (ExecuteInParallel) {
+      CommandsStarted.emplace_back(sys::ExecuteNoWait(
+          Prog, Args, /*Env=*/None, /*Redirects=*/None, /*MemoryLimit=*/0));
+      continue;
+    }
+
     int Result =
         sys::ExecuteAndWait(Prog, Args, /*Env=*/None, /*Redirects=*/None,
                             /*SecondsToWait=*/0, /*MemoryLimit=*/0, &ErrMsg);
@@ -232,6 +244,19 @@ int main(int argc, char **argv) {
     }
   }
 
+  // Wait for all commands to be executed.
+  std::string ErrMsg;
+  auto It = CommandsStarted.begin();
+  while (It != CommandsStarted.end()) {
+    sys::ProcessInfo WaitResult =
+        sys::Wait(*It, 0, /*WaitUntilTerminates*/ true, &ErrMsg);
+    if (WaitResult.ReturnCode != 0) {
+      errs() << "llvm-foreach: " << ErrMsg << '\n';
+      Res = WaitResult.ReturnCode;
+    }
+    It = CommandsStarted.erase(It);
+  }
+
   if (!OutputFileList.empty()) {
     OS.close();
   }