== This week ==
* TCWG-619
- v8 LTO build with different options for x86 and aarch64.
- Reported upstream v8 LTO build failure on ARM.
- Tried to build chromium with FSF gcc, linaro binary release and
linaro-4.9-branch
* PR49551
- Not able to reproduce ICE with latest trunk (r221871).
* Misc
- College assignments submission and term end.
== Next Week ==
* TCWG-619
- Build chromium with linaro-4.9-branch and trunk.
- Prepare stats for LTO build with different options for v8 on x86 and aarch64
- Try building chromium with LTO with FSF trunk for arm
* TCWG-639:
- Add enhancement to header file flattening script.
== Progress ==
Friday holiday
* Automation Framework (CARD-1378 2/10)
- Power cut in the office
- Fixing gateway, rebooting machines
- Mob management
* LLVM ARM Maintenance (CARD-1833 2/10)
- ARMTargetParser review
* Background (4/10)
- Code review, meetings, discussions, etc.
- All LLVM buildbots broken (one still)
- Trying to merge Android round/exception
- https://android-review.googlesource.com/#/c/125910/1
- Not that easy, will need bigger changes and tests to go in
== Plan ==
* Long holidays
* EuroLLVM
* Back on the 15th
Hi,
I did some tests on the following function
--- CUT HERE ---
int fibo(int n)
{
if (n < 2) return 1;
return (fibo(n-2) + fibo(n-1));
}
--- CUT HERE ---
and I discovered that it is faster -O2 than -O3. This is with gcc 4.9.2.
Looking at the disassembly I see it is using FP registers to hold
integer values. The following is a small extract.
.L3:
fmov w0, s8
sub w25, w25, #1
cmn w25, #1
add w0, w0, w27
fmov s8, w0
bne .L19
add w0, w0, 1
b .L2
Recompiling with -mgeneral-regs-only generates a huge improvement.
The following are the times I get on various partner HW. I have
normalised the -O2 times to 1 second so that I do not disclose actual
partner performance data:
Partner 1: -O2 = 1sec, -O3 = 1.13sec, -O3 -mgeneral-regs-only = 0.72sec
Partner 2: -O2 = 1sec, -O3 = 0.68sec, -O3 -mgeneral-regs-only = 0.60sec
Partner 3: -O2 = 1sec, -O3 = 0.73sec, -O3 -mgeneral-regs-only = 0.68sec
Partner 4: -O2 = 1sec, -O3 = 0.83sec, -O3 -mgeneral-regs-only = 0.84sec
So, in general, -O3 does actually do better than -O2, but in all cases
performance is better if I stop it using FP registers for int values.
I have put a tarball of the test program along with 3 binaries and 3
disassemblies here:-
http://people.linaro.org/~edward.nevill/fibo.tar
All the best,
Ed.
Hi,
I'm seeing the following build error trying to build from the current master
branch (1ac806b) of http://git.linaro.org/toolchain/binutils-gdb.
make[3]: *** No rule to make target `-L../zlib', needed by `run'. Stop.
make[3]: *** Waiting for unfinished jobs....
make[3]: Leaving directory `gdb/sim/arm'
The following commit predating the zlib changes appears to build without error.
b19a8f8545100a08ee2a64c05631aff6f651faa1
Thanks,
Chris
--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
