[GN] Define USE_EABI_HARDFLOAT=1 when arm_float_abi=="hard".

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/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 if (is_android) {
@@ skipping 125 matching lines @@
   }
 }
 
 config("toolchain") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   defines = []
   cflags = []
 
   # TODO(jochen): Add support for arm subarchs, mips, mipsel, mips64el.
-
   if (v8_target_arch == "arm") {
     defines += [ "V8_TARGET_ARCH_ARM" ]
     if (current_cpu == "arm") {
       if (arm_version == 7) {
         defines += [ "CAN_USE_ARMV7_INSTRUCTIONS" ]
       }
       if (arm_fpu == "vfpv3-d16") {
         defines += [ "CAN_USE_VFP3_INSTRUCTIONS" ]
       } else if (arm_fpu == "vfpv3") {
         defines += [
           "CAN_USE_VFP3_INSTRUCTIONS",
           "CAN_USE_VFP32DREGS",
         ]
       } else if (arm_fpu == "neon") {
         defines += [
           "CAN_USE_VFP3_INSTRUCTIONS",
           "CAN_USE_VFP32DREGS",
           "CAN_USE_NEON",
         ]
       }
     } else {
       # These defines ares used for the ARM simulator.
       defines += [
         "CAN_USE_ARMV7_INSTRUCTIONS",
         "CAN_USE_VFP3_INSTRUCTIONS",
         "CAN_USE_VFP32DREGS",
-        "USE_EABI_HARDFLOAT=0",
       ]
+
+      if (arm_float_abi == "hard") {

[slan, 2016/03/29 17:03:23]

Although this passes all the tryjobs, I've just discovered that arm_float_abi is
only declared when current_cpu == "arm". This is going to be an issue, as we
need to check this value to build a tool on the *host* (when target_cpu is "x86"
or "x64". I did not discover this until now, because Chromecast sets this value
in args.gn, giving it global visibility due to a GN KI.

In this case, we need to understand the ABI for the *target* toolchain, not the
current toolchain to set this define correctly.

Dirk: How do you feel about removing the if (current_toolchain == "arm")
condition from the delcaration in arm.gni? This would remove a developer
safeguard, but it would enable us to use the args as if their intent is to
describe the *target* (which I think is always the case).

Alternatively, we could add another arg in here, like v8_target_arm_float_abi,
but that is less preferable in my mind.

Thoughts?

[Dirk Pranke, 2016/03/29 21:03:40]

I assume you mean "(when current_cpu is "x86" or "x64")", right? target_cpu is 
effectively a constant and should be == "arm" across all toolchains; I don't
know
why you would need the arm args if target_cpu != "arm" or "arm64".

As an aside, it's important to distinguish between the host toolchain (which
should
always be x64) and the snapshot toolchain (which should be x86 for arm and x64
for
arm64).
I think we could probably change (current_cpu == "arm") to (target_cpu == "arm")
instead, which is probably what the intent actually is.
I think we can probably avoid that.

Let me know if my suggestions above work.

[slan, 2016/03/29 23:45:08]

Yes, that is what I meant! Thanks for seeing through the typo :)
I like this idea:
https://codereview.chromium.org/1842833003/
Thanks for the review!

+        defines += [ "USE_EABI_HARDFLOAT=1" ]
+      } else if (arm_float_abi == "softfp") {
+        defines += [ "USE_EABI_HARDFLOAT=0" ]
+      }
     }
 
     # TODO(jochen): Add support for arm_test_noprobe.
   }
   if (v8_target_arch == "arm64") {
     defines += [ "V8_TARGET_ARCH_ARM64" ]
   }
   if (v8_target_arch == "mipsel") {
     defines += [ "V8_TARGET_ARCH_MIPS" ]
   }
   if (v8_target_arch == "mips64el") {
     defines += [ "V8_TARGET_ARCH_MIPS64" ]
   }
   if (v8_target_arch == "s390") {
     defines += [ "V8_TARGET_ARCH_S390" ]
-  } 
+  }
   if (v8_target_arch == "s390x") {
     defines += [
       "V8_TARGET_ARCH_S390",
       "V8_TARGET_ARCH_S390X",
     ]
   }
   if (v8_target_arch == "x86") {
     defines += [ "V8_TARGET_ARCH_IA32" ]
   }
   if (v8_target_arch == "x64") {
     defines += [ "V8_TARGET_ARCH_X64" ]
   }
-     
+
   if (is_win) {
     defines += [ "WIN32" ]
     # TODO(jochen): Support v8_enable_prof.
   }
 
   # TODO(jochen): Add support for compiling with simulators.
 
   if (is_debug) {
     # TODO(jochen): Add support for different debug optimization levels.
     defines += [
@@ skipping 1881 matching lines @@
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [
     ":internal_config",
     ":libplatform_config",
     ":features",
     ":toolchain",
   ]
 }