Add Makefile options to build for the Raspberry Pi (armv7=0, arm_fpu=fvp2).

Add Makefile options to build for the Raspberry Pi (armv7=0, arm_fpu=vfp2).

With these Makefile changes, it is possible to build V8 on the Raspberry Pi with the following make invocation:

make native armv7=false vfp3=off hardfp=on disassembler=on console=readline snapshot=on gdbjit=on strictaliasing=off

R=danno@chromium.org
BUG=

Committed: https://code.google.com/p/v8/source/detail?r=13297

[danno, 2013-01-02 09:06:38]

Adding Yang and Jakob to look at ARM VFP flags and build file changes,
respectively.

[Yang, 2013-01-02 09:41:19]

some comments.

https://codereview.chromium.org/11722003/diff/1/Makefile
File Makefile (right):

https://codereview.chromium.org/11722003/diff/1/Makefile#newcode100
Makefile:100: GYPFLAGS += -Dv8_can_use_vfp3_instructions=true
I suggest adding -Darm_fpu=vfp3 here. Otherwise, specifying vfp2=on vfp3=on
would actually disable vfp3. (I assume appending to GYPFLAGS overrides previous
settings, in this case, the value of arm_fpu?)

[luismreis, 2013-01-02 11:44:24]

Hi,

Added the -Darm_fpu=vfp3. I've started a build with this options (vfp2=on
vfp3=on) and it seems that your assumption regarding gyp is correct.

From what I understand of the Makefile and the gyp files, this is somewhat
superfluous since a vfp3 is on by default (set by build/standalone.gypi) and a
vfp3 build make invocation should be just:

make native disassembler=on console=readline snapshot=on gdbjit=on
strictaliasing=off

(no arm options at all).

[Jakob Kummerow, 2013-01-02 16:30:28]

LGTM.

> a vfp3 build make invocation should be just:
> 
> make native disassembler=on console=readline snapshot=on gdbjit=on
> strictaliasing=off

disassembler=on is only useful for debugging (--print-code and friends), it is
not required for regular use.
snapshot=on is the default, no need to specify it.
gdbjit=on is only useful for debugging with GDB, but "make native" produces a
Release-mode binary, so you won't have much fun GDB'ing that anyway.
strictaliasing=off is a workaround for buggy compilers (GCC-4.5), it is not
usually required. Especially for ARM, you should use a more recent compiler
anyway (4.7+), as they produce much better code.
For more details, see http://code.google.com/p/v8/wiki/BuildingWithGYP.

Our build system is designed so that "make arm.release" or "make arm.debug" is
usually all you need.

[luismreis, 2013-01-02 17:24:17]

Thanks a lot for the tips!

The default compiler on the standard raspberry installation is gcc 4.6 - I'm
about to test 4.7 now.

I know that except for strictaliasing the those options aren't really necessary,
I just want to have a build with all the debug options turned on.

I'll send more feedback (if you're interested).

On 2013/01/02 16:30:28, Jakob wrote:
> LGTM.
> 
> > a vfp3 build make invocation should be just:
> > 
> > make native disassembler=on console=readline snapshot=on gdbjit=on
> > strictaliasing=off
> 
> disassembler=on is only useful for debugging (--print-code and friends), it is
> not required for regular use.
> snapshot=on is the default, no need to specify it.
> gdbjit=on is only useful for debugging with GDB, but "make native" produces a
> Release-mode binary, so you won't have much fun GDB'ing that anyway.
> strictaliasing=off is a workaround for buggy compilers (GCC-4.5), it is not
> usually required. Especially for ARM, you should use a more recent compiler
> anyway (4.7+), as they produce much better code.
> For more details, see http://code.google.com/p/v8/wiki/BuildingWithGYP.
> 
> Our build system is designed so that "make arm.release" or "make arm.debug" is
> usually all you need.

[Yang, 2013-01-03 08:55:33]

On 2013/01/02 17:24:17, luismreis wrote:
> Thanks a lot for the tips!
> 
> The default compiler on the standard raspberry installation is gcc 4.6 - I'm
> about to test 4.7 now.
> 
> I know that except for strictaliasing the those options aren't really
necessary,
> I just want to have a build with all the debug options turned on.
> 
> I'll send more feedback (if you're interested).
> 
> On 2013/01/02 16:30:28, Jakob wrote:
> > LGTM.
> > 
> > > a vfp3 build make invocation should be just:
> > > 
> > > make native disassembler=on console=readline snapshot=on gdbjit=on
> > > strictaliasing=off
> > 
> > disassembler=on is only useful for debugging (--print-code and friends), it
is
> > not required for regular use.
> > snapshot=on is the default, no need to specify it.
> > gdbjit=on is only useful for debugging with GDB, but "make native" produces
a
> > Release-mode binary, so you won't have much fun GDB'ing that anyway.
> > strictaliasing=off is a workaround for buggy compilers (GCC-4.5), it is not
> > usually required. Especially for ARM, you should use a more recent compiler
> > anyway (4.7+), as they produce much better code.
> > For more details, see http://code.google.com/p/v8/wiki/BuildingWithGYP.
> > 
> > Our build system is designed so that "make arm.release" or "make arm.debug"
is
> > usually all you need.

LGTM. Landing.

[luismreis, 2013-01-03 14:47:49]

Just as a follow up:

GCC 4.7 works perfectly fine without the strict aliasing option.

Current make invocation:
make arm.release armv7=false vfp3=off hardfp=on

On 2013/01/02 16:30:28, Jakob wrote:
> LGTM.
> 
> > a vfp3 build make invocation should be just:
> > 
> > make native disassembler=on console=readline snapshot=on gdbjit=on
> > strictaliasing=off
> 
> disassembler=on is only useful for debugging (--print-code and friends), it is
> not required for regular use.
> snapshot=on is the default, no need to specify it.
> gdbjit=on is only useful for debugging with GDB, but "make native" produces a
> Release-mode binary, so you won't have much fun GDB'ing that anyway.
> strictaliasing=off is a workaround for buggy compilers (GCC-4.5), it is not
> usually required. Especially for ARM, you should use a more recent compiler
> anyway (4.7+), as they produce much better code.
> For more details, see http://code.google.com/p/v8/wiki/BuildingWithGYP.
> 
> Our build system is designed so that "make arm.release" or "make arm.debug" is
> usually all you need.