GN: Add support for 32- and 64-bit cross-compiles.

This makes it possible on Linux to refer to 64-bit targets from a 32-bit build, and 32-bit targets from a 64-bit build.

This also adds flags for Mac cross-compiles but I haven't written the toolchain definitions yet.

BUG=322106
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/81153003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236871 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 133 insertions, 45 deletions

diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn
index f67106b..de1ee08b 100644
--- a/build/config/BUILDCONFIG.gn
+++ b/build/config/BUILDCONFIG.gn
@@ -383,20 +383,32 @@ set_defaults("source_set") {
 # default toolchain.
 
 if (is_win) {
-  if (cpu_arch == "x64") {
+  if (build_cpu_arch == "x64") {
     host_toolchain = "//build/toolchain/win:64"
-  } else if (cpu_arch == "x86") {
+  } else if (build_cpu_arch == "x86") {
     host_toolchain = "//build/toolchain/win:32"
   }
-  set_default_toolchain(host_toolchain)
+
+  if (cpu_arch == "x64") {
+    set_default_toolchain("//build/toolchain/win:64")
+  } else if (cpu_arch == "x86") {
+    set_default_toolchain("//build/toolchain/win:32")
+  }
 } else if (is_linux) {
-  host_toolchain = "//build/toolchain/linux:host"
-  if (cpu_arch == "arm" && build_cpu_arch != "arm") {
-    # Special toolchain for ARM cross-compiling.
-    set_default_toolchain("//build/toolchain/linux:arm-cross-compile")
-  } else {
-    # Use whatever GCC is on the current platform.
-    set_default_toolchain(host_toolchain)
+  if (build_cpu_arch == "arm") {
+    host_toolchain = "//build/toolchain/linux:arm"
+  } else if (build_cpu_arch == "x86") {
+    host_toolchain = "//build/toolchain/linux:32"
+  } else if (build_cpu_arch == "x64") {
+    host_toolchain = "//build/toolchain/linux:64"
+  }
+
+  if (build_cpu_arch == "arm") {
+    set_default_toolchain("//build/toolchain/linux:arm")
+  } else if (build_cpu_arch == "x86") {
+    set_default_toolchain("//build/toolchain/linux:32")
+  } else if (build_cpu_arch == "x64") {
+    set_default_toolchain("//build/toolchain/linux:64")
   }
 } else if (is_mac) {
   host_toolchain = "//build/toolchain/mac:clang"
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 6f69e05..2ded34e 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -39,14 +39,12 @@ config("compiler") {
       cflags += [ "-fstack-protector", "--param=ssp-buffer-size=4" ]
     }
 
-    # Mac-specific compiler flags setup.
-    # ----------------------------------
     if (is_mac) {
+      # Mac-specific compiler flags setup.
+      # ----------------------------------
+
       # These flags are shared between the C compiler and linker.
       common_mac_flags = [
-        # TODO(brettw) obviously this arch flag needs to be parameterized.
-        "-arch i386",
-
         # Set which SDK to use.
         # TODO(brettw) this needs to be configurable somehow.
         "-isysroot", "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk",
@@ -54,6 +52,13 @@ config("compiler") {
         "-mmacosx-version-min=10.6",
       ]
 
+      # CPU architecture.
+      if (cpu_arch == "x64") {
+        common_mac_flags += "-arch x86_64"
+      } else if (cpu_arch == "x32") {
+        common_mac_flags += "-arch i386"
+      }
+
       cflags += common_mac_flags + [
         # Without this, the constructors and destructors of a C++ object inside
         # an Objective C struct won't be called, which is very bad.
@@ -70,6 +75,19 @@ config("compiler") {
         "-Wl,-rpath,@loader_path/.",
         "-Wl,-rpath,@loader_path/../../..",
       ]
+    } else {
+      # Non-Mac Posix compiler flags setup.
+      # -----------------------------------
+
+      # CPU architecture. We may or may not be doing a cross compile now, so for
+      # simplicity we always explicitly set the architecture.
+      if (cpu_arch == "x64") {
+        cflags += "-m64"
+        ldflags += "-m64"
+      } else if (cpu_arch == "x32") {
+        cflags += "-m32"
+        ldflags += "-m32"
+      }
     }
 
     # Linux-specific compiler flags setup.
diff --git a/build/toolchain/linux/BUILD.gn b/build/toolchain/linux/BUILD.gn
index 016bf29..ffb378b 100644
--- a/build/toolchain/linux/BUILD.gn
+++ b/build/toolchain/linux/BUILD.gn
@@ -7,116 +7,174 @@ cxx = "g++"
 ar = "ar"
 ld = cxx
 
-# Everything up to the toolchain args is an exact copy of the GCC version
-# below. Keep in sync! Only the compiler variable definitions have changed.
-toolchain("host") {
+# The toolchains below all issue the same commands with some different flags.
+# TODO(brettw) it would be nice to have a different way to express this without
+# so much duplication.
+cc_command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c -c \$in -o \$out"
+cxx_command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc -c \$in -o \$out"
+alink_command = "rm -f \$out && $ar rcs \$out \$in"
+solink_command = "if [ ! -e \$lib -o ! -e \${lib}.TOC ]; then $ld -shared \$ldflags -o \$lib -Wl,-soname=\$soname -Wl,--whole-archive \$in \$solibs -Wl,--no-whole-archive \$libs && { readelf -d \${lib} | grep SONAME ; nm -gD -f p \${lib} | cut -f1-2 -d' '; } > \${lib}.TOC; else $ld -shared \$ldflags -o \$lib -Wl,-soname=\$soname -Wl,--whole-archive \$in \$solibs -Wl,--no-whole-archive \$libs && { readelf -d \${lib} | grep SONAME ; nm -gD -f p \${lib} | cut -f1-2 -d' '; } > \${lib}.tmp && if ! cmp -s \${lib}.tmp \${lib}.TOC; then mv \${lib}.tmp \${lib}.TOC ; fi; fi"
+link_command = "$ld \$ldflags -o \$out -Wl,--start-group \$in \$solibs -Wl,--end-group \$libs"
+stamp_command = "\${postbuilds}touch \$out"
+copy_command = "ln -f \$in \$out 2>/dev/null || (rm -rf \$out && cp -af \$in \$out)"
+
+# ARM --------------------------------------------------------------------------
+
+cc = "arm-linux-gnueabi-gcc"
+cxx = "arm-linux-gnueabi-g++"
+ar = "arm-linux-gnueabi-ar"
+ld = cxx
+
+toolchain("arm") {
   # Make these apply to all tools below.
   lib_prefix = "-l"
   lib_dir_prefix="-L"
 
   tool("cc") {
     # cflags_pch_c
-    command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c -c \$in -o \$out"
+    command = cc_command
     description = "CC \$out"
     depfile = "\$out.d"
     deps = "gcc"
   }
   tool("cxx") {
     # cflags_pch_cc
-    command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc -c \$in -o \$out"
+    command = cxx_command
     description = "CXX \$out"
     depfile = "\$out.d"
     deps = "gcc"
   }
   tool("alink") {
-    command = "rm -f \$out && $ar rcs \$out \$in"
+    command = alink_command
     description = "AR \$out"
   }
   tool("solink") {
-    command = "if [ ! -e \$lib -o ! -e \${lib}.TOC ]; then $ld -shared \$ldflags -o \$lib -Wl,-soname=\$soname -Wl,--whole-archive \$in \$solibs -Wl,--no-whole-archive \$libs && { readelf -d \${lib} | grep SONAME ; nm -gD -f p \${lib} | cut -f1-2 -d' '; } > \${lib}.TOC; else $ld -shared \$ldflags -o \$lib -Wl,-soname=\$soname -Wl,--whole-archive \$in \$solibs -Wl,--no-whole-archive \$libs && { readelf -d \${lib} | grep SONAME ; nm -gD -f p \${lib} | cut -f1-2 -d' '; } > \${lib}.tmp && if ! cmp -s \${lib}.tmp \${lib}.TOC; then mv \${lib}.tmp \${lib}.TOC ; fi; fi"
+    command = solink_command
     description = "SOLINK \$lib"
     #pool = "link_pool"
     restat = "1"
   }
   tool("link") {
-    command = "$ld \$ldflags -o \$out -Wl,--start-group \$in \$solibs -Wl,--end-group \$libs"
+    command = link_command
     description = "LINK \$out"
     #pool = "link_pool"
   }
   tool("stamp") {
-    command = "\${postbuilds}touch \$out"
+    command = stamp_command
     description = "STAMP \$out"
   }
   tool("copy") {
-    command = "ln -f \$in \$out 2>/dev/null || (rm -rf \$out && cp -af \$in \$out)"
+    command = copy_command
     description = "COPY \$in \$out"
   }
 
   # When invoking this toolchain not as the default one, these args will be
   # passed to the build. They are ignored when this is the default toolchain.
   toolchain_args() {
-    # Pass the current CPU architecture to the build as the toolchain to use.
-    # If the default toolchain is set to ARM and the local system is x86, this
-    # will make this secondary toolchain refer to the host GCC again.
-    cpu_arch = build_cpu_arch
+    cpu_arch = "arm"
   }
 }
 
-# ARM Cross-Compile ------------------------------------------------------------
+# 32-bit -----------------------------------------------------------------------
 
-cc = "arm-linux-gnueabi-gcc"
-cxx = "arm-linux-gnueabi-g++"
-ar = "arm-linux-gnueabi-ar"
-ld = cxx
+toolchain("32") {
+  # Make these apply to all tools below.
+  lib_prefix = "-l"
+  lib_dir_prefix="-L"
+
+  tool("cc") {
+    # cflags_pch_c
+    command = cc_command
+    description = "CC \$out"
+    depfile = "\$out.d"
+    deps = "gcc"
+  }
+  tool("cxx") {
+    # cflags_pch_cc
+    command = cxx_command
+    description = "CXX \$out"
+    depfile = "\$out.d"
+    deps = "gcc"
+  }
+  tool("alink") {
+    command = alink_command
+    description = "AR \$out"
+  }
+  tool("solink") {
+    command = solink_command
+    description = "SOLINK \$lib"
+    #pool = "link_pool"
+    restat = "1"
+  }
+  tool("link") {
+    command = link_command
+    description = "LINK \$out"
+    #pool = "link_pool"
+  }
+  tool("stamp") {
+    command = stamp_command
+    description = "STAMP \$out"
+  }
+  tool("copy") {
+    command = copy_command
+    description = "COPY \$in \$out"
+  }
 
-# Everything up the the toolchain args is an exact copy of the GCC version
-# below. Keep in sync! Only the compiler variable definitions have changed.
-toolchain("arm-cross-compile") {
+  # When invoking this toolchain not as the default one, these args will be
+  # passed to the build. They are ignored when this is the default toolchain.
+  toolchain_args() {
+    cpu_arch = "x32"
+  }
+}
+
+# 64-bit -----------------------------------------------------------------------
+
+toolchain("64") {
   # Make these apply to all tools below.
   lib_prefix = "-l"
   lib_dir_prefix="-L"
 
   tool("cc") {
     # cflags_pch_c
-    command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c -c \$in -o \$out"
+    command = cc_command
     description = "CC \$out"
     depfile = "\$out.d"
     deps = "gcc"
   }
   tool("cxx") {
     # cflags_pch_cc
-    command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc -c \$in -o \$out"
+    command = cxx_command
     description = "CXX \$out"
     depfile = "\$out.d"
     deps = "gcc"
   }
   tool("alink") {
-    command = "rm -f \$out && $ar rcs \$out \$in"
+    command = alink_command
     description = "AR \$out"
   }
   tool("solink") {
-    command = "if [ ! -e \$lib -o ! -e \${lib}.TOC ]; then $ld -shared \$ldflags -o \$lib -Wl,-soname=\$soname -Wl,--whole-archive \$in \$solibs -Wl,--no-whole-archive \$libs && { readelf -d \${lib} | grep SONAME ; nm -gD -f p \${lib} | cut -f1-2 -d' '; } > \${lib}.TOC; else $ld -shared \$ldflags -o \$lib -Wl,-soname=\$soname -Wl,--whole-archive \$in \$solibs -Wl,--no-whole-archive \$libs && { readelf -d \${lib} | grep SONAME ; nm -gD -f p \${lib} | cut -f1-2 -d' '; } > \${lib}.tmp && if ! cmp -s \${lib}.tmp \${lib}.TOC; then mv \${lib}.tmp \${lib}.TOC ; fi; fi"
+    command = solink_command
     description = "SOLINK \$lib"
     #pool = "link_pool"
     restat = "1"
   }
   tool("link") {
-    command = "$ld \$ldflags -o \$out -Wl,--start-group \$in \$solibs -Wl,--end-group \$libs"
+    command = link_command
     description = "LINK \$out"
     #pool = "link_pool"
   }
   tool("stamp") {
-    command = "\${postbuilds}touch \$out"
+    command = stamp_command
     description = "STAMP \$out"
   }
   tool("copy") {
-    command = "ln -f \$in \$out 2>/dev/null || (rm -rf \$out && cp -af \$in \$out)"
+    command = copy_command
     description = "COPY \$in \$out"
   }
 
   # When invoking this toolchain not as the default one, these args will be
   # passed to the build. They are ignored when this is the default toolchain.
   toolchain_args() {
-    cpu_arch = "arm"
+    cpu_arch = "x64"
   }
 }