[Webkit-unassigned] [Bug 175514] [GTK] ARMv7 build fails to build MacroAssemblerARMv7.cpp.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=175514

Carlos Alberto Lopez Perez <clopez at igalia.com> changed:

           What    |Removed                     |Added
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                 CC|                            |aperez at igalia.com

--- Comment #6 from Carlos Alberto Lopez Perez <clopez at igalia.com> ---
(In reply to Mark Lam from comment #5)
> To green the GTX bots, I've disabled the DFG for GTK ARM_THUMB2 in r220816:
> <http://trac.webkit.org/r220816>.
> 
> Please re-enabled the DFG when this issue is fixed.

It looks is still broken?

(In reply to Carlos Alberto Lopez Perez from comment #4)
> This may be related to the FPU the compiler assume it can use. More info:
> https://stackoverflow.com/a/33904219
> 
> Kov, can you please paste here the output of running "gcc -v" on the ARM
> buildbot (to see which "--with-fpu" parameter it was built with)?

This is the output of gcc -v on Debian armhf (The GTK+ ARM bot runs on Debian)

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/arm-linux-gnueabihf/6/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18' --with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-6 --program-prefix=arm-linux-gnueabihf- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --enable-plugin --enable-default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-armhf/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-armhf --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-armhf --with-arch-directory=arm --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --disable-sjlj-exceptions --with-arch=armv7-a --with-fpu=vfpv3-d16 --with-float=hard --with-mode=thumb --enable-checking=release --build=arm-linux-gnueabihf --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf
Thread model: posix
gcc version 6.3.0 20170516 (Debian 6.3.0-18) 


So, by default its building with --with-fpu=vfpv3-d16

Which according to the GCC help <https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html> means:

‘+vfpv3-d16’

    The VFPv3 floating-point instructions, with 16 double-precision registers.

And the ARM help says this: <http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0473c/Bcfhdhgd.html>

So, my understanding is that when building with --with-fpu=vfpv3-d16 only the double-precision registers d0-d15 are available.

To access the double-precision registers beyond d15 (d16-d31) we need to build with vfpv4/neon or something like -mfpu=vfpv3-fp16


I'm unsure about the consequences of requiring a vfpu with 32 double-precision registers. Do all ARMv7 CPUs support this???

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