Add the mips_dsp_rev build variable.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium 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/config/android/config.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
   import("//build/config/mips.gni")
@@ skipping 283 matching lines @@
           cflags += [
             "-mips32r2",
             "-Wa,-mips32r2",
           ]
         } else if (mips_arch_variant == "r1") {
           cflags += [
             "-mips32",
             "-Wa,-mips32",
           ]
         }
+
+        if (mips_dsp_rev == 1) {
+          cflags += [ "-mdsp" ]
+        } else if (mips_dsp_rev == 2) {
+          cflags += [ "-mdspr2" ]
+        }
+
+        if (mips_float_abi == "hard") {
+          cflags += [ "-mhard-float" ]

[kjellander_chromium, 2015/02/25 21:08:07]

I think line 311-315 can be replaced with a single line:
cflags += [ "-m$mips_float_abi-float" ]
but I'll leave it to you to try it out.

[wtc, 2015/02/27 05:57:19]

Done. I added curly braces {} around the variable to improve readability.

Originally I didn't want to do this because I like being able to search for a
compiler flag by name. I came up with a good solution: I now document the
compiler flags in the comments for mips_float_abi.

+        } else {
+          cflags += [ "-msoft-float" ]
+        }
+
+        if (mips_arch_variant == "r2") {
+          if (mips_fpu_mode == "fp32") {

[kjellander_chromium, 2015/02/25 21:08:07]

I think line 318-324 could be replaced with a single line:
cflags += [ "-m$mips_fpu_mode" ]
unless it can have another value too, which shouldn't result in a cflag getting
added?

[petarj, 2015/02/26 01:35:43]

It can be undefined (if FPU unit is not present), see the case above
(mips_float_abi). We could merge it with that, though I am fine with this
way as well.

[wtc, 2015/02/27 05:57:19]

I added an empty string check, so it is three lines:

  if (mips_fpu_mode != "") {
    cflags += [ "-m$mips_fpu_mode" ]
  }

+            cflags += [ "-mfp32" ]
+          } else if (mips_fpu_mode == "fp64") {
+            cflags += [ "-mfp64" ]
+          } else if (mips_fpu_mode == "fpxx") {
+            cflags += [ "-mfpxx" ]
+          }
+        }
       }
     } else if (current_cpu == "mips64el") {
       # Don't set the compiler flags for the WebView build. These will come
       # from the Android build system.
       if (!is_android_webview_build) {
         if (mips_arch_variant == "r6") {
           cflags += [
             "-mips64r6",
             "-Wa,-mips64r6",
           ]
@@ skipping 760 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }