Add a [rtc_]build_with_neon variable to unify conditions.

webrtc/modules/audio_coding/BUILD.gn

Index: webrtc/modules/audio_coding/BUILD.gn
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index 7b7acd34d8b93e6c3b3dd50e6f3dc366e26b99ab..21ebd51364bd630baf65d667a2af91f26a6cdcff 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -498,6 +498,7 @@ source_set("isac_fix") {
     "codecs/isac/fix/source/initialize.c",
     "codecs/isac/fix/source/isacfix.c",
     "codecs/isac/fix/source/lattice.c",
+    "codecs/isac/fix/source/lattice_c.c",
     "codecs/isac/fix/source/lpc_masking_model.c",
     "codecs/isac/fix/source/lpc_masking_model.h",
     "codecs/isac/fix/source/lpc_tables.c",
@@ -536,27 +537,19 @@ source_set("isac_fix") {
     "../../system_wrappers",
   ]
 
-  if (current_cpu == "arm64") {
+  if (rtc_build_with_neon) {
     deps += [ ":isac_neon" ]
   }
 
-  if (rtc_build_armv7_neon) {
-    deps += [ ":isac_neon" ]
-
-    # Enable compilation for the ARM v7 Neon instruction set. This is needed
-    # since //build/config/arm.gni only enables Neon for iOS, not Android.
-    # This provides the same functionality as webrtc/build/arm_neon.gypi.
-    # TODO(kjellander): Investigate if this can be moved into webrtc.gni or
-    # //build/config/arm.gni instead, to reduce code duplication.
-    # Remove the -mfpu=vfpv3-d16 cflag.
-    configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
-    cflags = [ "-mfpu=neon" ]
-
+  if (current_cpu == "arm" && arm_version >= 7) {

[Andrew MacDonald, 2015/06/17 17:44:16]

I know the armv6 file below doesn't require arm_version >= 7, but I honestly
don't think it's worth adding another condition for it.

[jridges, 2015/06/17 18:46:51]

I agree, especially since the plan is to get rid of the .S files eventually
anyway.

     sources += [
       "codecs/isac/fix/source/lattice_armv7.S",
       "codecs/isac/fix/source/pitch_filter_armv6.S",
     ]
-    sources -= [ "codecs/isac/fix/source/pitch_filter_c.c" ]
+    sources -= [
+      "codecs/isac/fix/source/lattice_c.c",
+      "codecs/isac/fix/source/pitch_filter_c.c",
+    ]
   }
 
   if (current_cpu == "mipsel") {
@@ -567,7 +560,10 @@ source_set("isac_fix") {
       "codecs/isac/fix/source/pitch_estimator_mips.c",
       "codecs/isac/fix/source/transform_mips.c",
     ]
-    sources -= [ "codecs/isac/fix/source/pitch_estimator_c.c" ]
+    sources -= [
+      "codecs/isac/fix/source/lattice_c.c",
+      "codecs/isac/fix/source/pitch_estimator_c.c",
+    ]
     if (mips_dsp_rev > 0) {
       sources += [ "codecs/isac/fix/source/filterbanks_mips.c" ]
     }
@@ -579,13 +575,9 @@ source_set("isac_fix") {
       sources -= [ "codecs/isac/fix/source/pitch_filter_c.c" ]
     }
   }
-
-  if (!rtc_build_armv7_neon && current_cpu != "mipsel") {
-    sources += [ "codecs/isac/fix/source/lattice_c.c" ]

[Andrew MacDonald, 2015/06/17 17:44:16]

I think adding this to the primary source list and removing it as appropriate
with each architecture is more clear. The gn file does it this way.

-  }
 }
 
-if (rtc_build_armv7_neon || current_cpu == "arm64") {
+if (rtc_build_with_neon) {
   source_set("isac_neon") {
     sources = [
       "codecs/isac/fix/source/entropy_coding_neon.c",
@@ -593,34 +585,17 @@ if (rtc_build_armv7_neon || current_cpu == "arm64") {
       "codecs/isac/fix/source/lattice_neon.c",
       "codecs/isac/fix/source/transform_neon.c",
     ]
-
-    if (rtc_build_armv7_neon) {
-      # Enable compilation for the ARM v7 Neon instruction set. This is needed
-      # since //build/config/arm.gni only enables Neon for iOS, not Android.
-      # This provides the same functionality as webrtc/build/arm_neon.gypi.
-      # TODO(kjellander): Investigate if this can be moved into webrtc.gni or
-      # //build/config/arm.gni instead, to reduce code duplication.
-      # Remove the -mfpu=vfpv3-d16 cflag.
-      configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
-      cflags = [ "-mfpu=neon" ]
-    }
-
     if (current_cpu != "arm64" || !is_clang) {
       # Disable AllpassFilter2FixDec16Neon function due to a clang bug.
-      # Refer more details at:
+      # For more details refer to:
       # https://code.google.com/p/webrtc/issues/detail?id=4567
       sources += [ "codecs/isac/fix/source/filterbanks_neon.c" ]
     }
 
-    # Disable LTO in audio_processing_neon target due to compiler bug.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
-
-    configs += [ "../..:common_config" ]
+    configs += [
+      "../..:arm_neon_config",
+      "../..:common_config",
+    ]
     public_configs = [ "../..:common_inherited_config" ]
 
     deps = [