[Arm]: Simplify compile-time Arm feature detection.

[Arm]: Simplify compile-time Arm feature detection.

Simplify the compile time feature detection on Arm:
 - Define CAN_USE_XXX definitions unconditionally for all target/host
   toolchain combinations
 - Rename arm_test / ARM_TEST to arm_test_noprob / ARM_TEST_NO_FEATURE_PROBE
 - Don't set ARM_TEST_NO_FEATURE_PROBE implicitly on the simulator to make
   make simulator / native more consistent
 - Unify CpuFeatures::PrintTarget for simulator and native builds
 - Remove unecessary CAN_USE_VFP_INSTRUCTIONS definition for android (this is
   the default for arm_fpu=default)
 - Add a CpuFeatures::Probe() before calling CpuFeatures::PrintFeatures() in PrintHelp
    to ensure we have probed features before printing them.

BUG=384474
LOG=N
R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21935

[rmcilroy, 2014-06-19 08:53:56]

Jakob, could you please review this CL.

Vincent / Rodolph, as mentioned in crbug.com/384474, this CL changes simulator
builds such that they don't implicitly set arm_test=on.  I think this is more
consistent with native builds.  As far as I know, you are the only people who
use the arm_test build flag - does this meet your needs?  

I tested this change with a number of configurations and the results seem
reasonable - results below:

===== ANDROID =====

=== make android_arm.release ===
--- snapshot --- 
target simulator arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=1 NEON=1 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0

=== make android_arm.release arm_fpu=neon ===
--- snapshot --- 
target simulator arm v7 neon softfp
ARMv7=1 VFP3=1 VFP32DREGS=1 NEON=1 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target arm v7 neon softfp
ARMv7=1 VFP3=1 VFP32DREGS=1 NEON=1 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0

=== make android_arm.release arm_test_noprobe=on  ===
--- snapshot --- 
target simulator noprobe arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target noprobe arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0

=== make android_arm.release arm_test_noprobe=on arm_version=6 armfpu=vp2 ===
--- snapshot --- 
target simulator noprobe arm v6 vfp2 softfp
ARMv7=0 VFP3=0 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=0
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target noprobe arm v6 vfp2 softfp
ARMv7=0 VFP3=0 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0


===== SIMULATOR =====
=== make arm.release ===
--- snapshot --- 
target simulator arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target simulator arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=1 NEON=1 SUDIV=1 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0

=== make arm.release arm_test_noprobe=on ===
--- snapshot --- 
target simulator noprobe arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target simulator noprobe arm v7 vfp3-d16 softfp
ARMv7=1 VFP3=1 VFP32DREGS=0 NEON=0 SUDIV=1 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0

=== make arm.release arm_test_noprobe=on arm_version=6 armfpu=vp2 ===
--- snapshot --- 
target simulator noprobe arm v6 vfp2 softfp
ARMv7=0 VFP3=0 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=0
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0
--- target ---
target simulator noprobe arm v6 vfp2 softfp
ARMv7=0 VFP3=0 VFP32DREGS=0 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1
MOVW_MOVT_IMMEDIATE_LOADS=0 USE_EABI_HARDFLOAT=0

[Rodolph Perfetta, 2014-06-19 09:59:56]

This works for us. Thanks.

[Jakob Kummerow, 2014-06-20 08:59:58]

lgtm

[rmcilroy, 2014-06-23 12:20:04]

Committed patchset #1 manually as r21935 (presubmit successful).