Simplify GN pools, use for some toolchain actions (#856)

Companion to flutter/engine#52721

Author: zanderso

build/toolchain/BUILD.gn

@@ -0,0 +1,9 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/toolchain/toolchain.gni")
+
+pool("toolchain_pool") {
+  depth = concurrent_toolchain_jobs
+}

build/toolchain/gcc_toolchain.gni

@@ -141,6 +141,7 @@ template("gcc_toolchain") {
     }
 
     tool("asm") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       depfile = "{{output}}.d"
       command = "$asm -MMD -MF$depfile {{defines}} {{include_dirs}} {{asmflags}} {{cflags}} {{cflags_c}} $coverage_flags -c {{source}} -o {{output}}"
       depsformat = "gcc"
@@ -150,6 +151,7 @@ template("gcc_toolchain") {
     }
 
     tool("alink") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       rspfile = "{{output}}.rsp"
       command = "rm -f {{output}} && $ar rcs {{output}} @$rspfile"
       description = "AR {{output}}"
@@ -161,6 +163,7 @@ template("gcc_toolchain") {
     }
 
     tool("solink") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
       sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
       rspfile = sofile + ".rsp"
@@ -228,6 +231,7 @@ template("gcc_toolchain") {
     }
 
     tool("link") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       exename = "{{target_output_name}}{{output_extension}}"
       outfile = "{{root_out_dir}}/$exename"
       rspfile = "$outfile.rsp"

build/toolchain/mac/BUILD.gn

@@ -115,6 +115,7 @@ template("mac_toolchain") {
     }
 
     tool("asm") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       depfile = "{{output}}.d"
       command = "$asm -MMD -MF $depfile {{defines}} {{include_dirs}} {{asmflags}} {{cflags}} {{cflags_c}} $sysroot_flags -c {{source}} -o {{output}}"
       depsformat = "gcc"
@@ -124,6 +125,7 @@ template("mac_toolchain") {
     }
 
     tool("objc") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       depfile = "{{output}}.d"
       command = "$objc -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} {{cflags_objc}} $sysroot_flags $coverage_flags -c {{source}} -o {{output}}"
       depsformat = "gcc"
@@ -133,6 +135,7 @@ template("mac_toolchain") {
     }
 
     tool("objcxx") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       depfile = "{{output}}.d"
       command = "$objc -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} {{cflags_objcc}} $sysroot_flags $coverage_flags -c {{source}} -o {{output}}"
       depsformat = "gcc"
@@ -142,6 +145,7 @@ template("mac_toolchain") {
     }
 
     tool("alink") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       command = "rm -f {{output}} && $ar rcs {{output}} {{inputs}}"
       description = "CREATE ARCHIVE {{output}}"
       outputs =
@@ -151,6 +155,7 @@ template("mac_toolchain") {
     }
 
     tool("solink") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       dylib = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"  # eg
                                                                              # "./libfoo.dylib"
       rspfile = dylib + ".rsp"
@@ -202,6 +207,7 @@ template("mac_toolchain") {
     }
 
     tool("link") {
+      pool = "//build/toolchain:toolchain_pool($current_toolchain)"
       outfile = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$outfile.rsp"
 

build/toolchain/toolchain.gni

@@ -1,9 +1,12 @@
-# Copyright 2020 The Flutter Authors. All rights reserved.
+# Copyright 2013 The Flutter Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   buildtools_path = "//buildtools"
+
+  # Maximum number of local toolchain tasks to run in parallel.
+  concurrent_toolchain_jobs = 1
 }
 
 use_xcode_clang = false