[MIPS64] Add support for building Chromium Linux for mips64r2

This change adds missing parts of mips64r2 support.

Bug: 800754
Change-Id: If37183b7c996effe28b7f687ca86ec7f11d90514
Reviewed-on: https://chromium-review.googlesource.com/860058
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#531691}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b6e93fc673900ede618341e9a5cfd66d9261954e

config/allocator.gni

@@ -5,9 +5,9 @@
 import("//build/config/sanitizers/sanitizers.gni")
 
 # Temporarily disable tcmalloc on arm64 linux to get rid of compilation errors.
-if (is_android || current_cpu == "mipsel" || is_mac || is_ios || is_asan ||
-    is_lsan || is_tsan || is_msan || is_win || is_syzyasan || is_fuchsia ||
-    (is_linux && target_cpu == "arm64")) {
+if (is_android || current_cpu == "mipsel" || current_cpu == "mips64el" ||
+    is_mac || is_ios || is_asan || is_lsan || is_tsan || is_msan || is_win ||
+    is_syzyasan || is_fuchsia || (is_linux && target_cpu == "arm64")) {
   _default_allocator = "none"
 } else {
   _default_allocator = "tcmalloc"

config/compiler/BUILD.gn

@@ -834,11 +834,18 @@ config("compiler_cpu_abi") {
           ]
         }
       } else if (mips_arch_variant == "r2") {
-        cflags += [
-          "-mips64r2",
-          "-Wa,-mips64r2",
-        ]
         ldflags += [ "-mips64r2" ]
+        if (is_clang) {
+          cflags += [
+            "-march=mips64el",
+            "-mcpu=mips64r2",
+          ]
+        } else {
+          cflags += [
+            "-mips64r2",
+            "-Wa,-mips64r2",
+          ]
+        }
       } else if (mips_arch_variant == "loongson3") {
         defines += [ "_MIPS_ARCH_LOONGSON" ]
         cflags += [

config/compiler/compiler.gni

@@ -169,8 +169,9 @@ declare_args() {
   use_gold =
       (!use_lld && !(is_chromecast && is_linux &&
                      (current_cpu == "arm" || current_cpu == "mipsel")) &&
-       (is_linux && (current_cpu == "x64" || current_cpu == "x86" ||
-                     current_cpu == "arm" || current_cpu == "mipsel"))) ||
+       (is_linux &&
+        (current_cpu == "x64" || current_cpu == "x86" || current_cpu == "arm" ||
+         current_cpu == "mipsel" || current_cpu == "mips64el"))) ||
       (is_android && (current_cpu == "x86" || current_cpu == "x64" ||
                       current_cpu == "arm" || current_cpu == "arm64"))
 }

config/sysroot.gni

@@ -15,9 +15,9 @@ declare_args() {
   # The absolute path to directory containing linux sysroot images
   target_sysroot_dir = "//build/linux"
 
-  use_sysroot =
-      current_cpu == "x86" || current_cpu == "x64" || current_cpu == "arm" ||
-      current_cpu == "arm64" || current_cpu == "mipsel"
+  use_sysroot = current_cpu == "x86" || current_cpu == "x64" ||
+                current_cpu == "arm" || current_cpu == "arm64" ||
+                current_cpu == "mipsel" || current_cpu == "mips64el"
 }
 
 if (current_os == target_os && current_cpu == target_cpu &&
@@ -37,6 +37,8 @@ if (current_os == target_os && current_cpu == target_cpu &&
     sysroot = "$target_sysroot_dir/debian_stretch_i386-sysroot"
   } else if (current_cpu == "mipsel") {
     sysroot = "$target_sysroot_dir/debian_stretch_mips-sysroot"
+  } else if (current_cpu == "mips64el") {
+    sysroot = "$target_sysroot_dir/debian_stretch_mips64el-sysroot"
   } else if (current_cpu == "arm") {
     sysroot = "$target_sysroot_dir/debian_stretch_arm-sysroot"
   } else if (current_cpu == "arm64") {