[Opus] Only include NEON sources and macros when arm_use_neon==true.

third_party/opus/BUILD.gn

 # Copyright 2014 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/arm.gni")
 import("//testing/test.gni")
 
 # If fixed point implementation shall be used (otherwise float).
 use_opus_fixed_point = current_cpu == "arm" || current_cpu == "arm64"
 
@@ skipping 348 matching lines @@
       "src/silk/arm/macros_armv4.h",
       "src/silk/arm/macros_armv5e.h",
     ]
 
     defines += [
       "OPUS_ARM_ASM",
       "OPUS_ARM_INLINE_ASM",
       "OPUS_ARM_INLINE_EDSP",
     ]
 
     if (use_opus_rtcd) {

[minyue, 2016/10/20 07:55:24]

If I am not mistaken, RTCD can determine neon at runtime, and
OPUS_ARM_MAY_HAVE_NEON is supposed to work with all compilers.

Would you add a bug issue (and update the BUG field in the CL's description)?
There you can write the way to reproduce the build error.

[wzhong, 2016/10/20 15:30:11]

Yeah. A bug would help.

The problem is the source file includes "arm_neon.h", which requres =mfpu=enon
for compiling.

Otherwise you'd get "You must enable NEON instructions (e.g. -mfloat-abi=softfp
-mfpu=neon) to use arm_neon.h".

https://cs.corp.google.com/eureka_internal/prebuilt/toolchain/armv7a/usr/lib/...

[slan, 2016/10/20 16:33:11]

Tagged the bug.

To your point, OPUS_ARM_MAY_HAVE_NEON sounds like it should work unconditionally
at runtime, with neon or not. However, there are lots of functions whose
callsites are guarded by these macros, with definitions in the excluded files.
So if we don't put these macros in the conditional, we have a bunch of missing
symbols.

       sources += [
         "$target_gen_dir/celt_pitch_xcorr_arm_gnu.S",
         "src/celt/arm/arm_celt_map.c",
         "src/celt/arm/armcpu.c",
         "src/celt/arm/armcpu.h",
-        "src/celt/arm/celt_neon_intr.c",
         "src/celt/arm/fft_arm.h",
         "src/celt/arm/mdct_arm.h",
         "src/celt/arm/pitch_arm.h",
-        "src/silk/arm/NSQ_neon.c",
-        "src/silk/arm/NSQ_neon.h",
         "src/silk/arm/arm_silk_map.c",
       ]
 
       include_dirs += [ "src" ]
 
       defines += [
         "OPUS_ARM_MAY_HAVE_EDSP",
         "OPUS_ARM_MAY_HAVE_MEDIA",
-        "OPUS_ARM_MAY_HAVE_NEON",
-        "OPUS_ARM_MAY_HAVE_NEON_INTR",
         "OPUS_HAVE_RTCD",
       ]
 
       deps = [
         ":convert_rtcd_assembler",
       ]
+
+      if (arm_use_neon) {
+        sources += [
+          "src/celt/arm/celt_neon_intr.c",
+          "src/silk/arm/NSQ_neon.c",
+          "src/silk/arm/NSQ_neon.h",
+        ]
+
+        defines += [
+          "OPUS_ARM_MAY_HAVE_NEON",
+          "OPUS_ARM_MAY_HAVE_NEON_INTR",
+        ]
+      }
     }
   }
 }
 
 executable("opus_compare") {
   sources = [
     "src/src/opus_compare.c",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
@@ skipping 97 matching lines @@
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     "//build/config/compiler:no_chromium_code",
     ":opus_test_config",
   ]
 
   deps = [
     ":opus",
   ]
 }