llvm dev - Jun 2010 - [LLVMdev] Tell LLVM JIT to omit the frame pointer?

> exactly
Well, in general, there is no connection between the performance on
x86 and on ARM.
You can try to profile your code and find what causes the speedup on
x86 and figure out the slowdowns on ARM.

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

Hey guys,

Is there a way to force the LLVM JIT compiler to omit the frame pointer in its
generated i386/amd64 code? I've got a complex situation in which the stack
can potentially be moved around so I'd prefer that the base pointer
doesn't get pushed there.

Félix

Take look at TargetOptions.h -
http://llvm.org/doxygen/TargetOptions_8h_source.html

I thought FPO is enabled by default (I explicitly disable it), but try setting:

llvm::NoFramePointerElim = false;

-----Original Message-----
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Félix Cloutier
Sent: Monday, June 28, 2010 9:49 AM
To: LLVM Developers Mailing List
Subject: [LLVMdev] Tell LLVM JIT to omit the frame pointer?

Hey guys,

Is there a way to force the LLVM JIT compiler to omit the frame pointer in its
generated i386/amd64 code? I've got a complex situation in which the stack
can potentially be moved around so I'd prefer that the base pointer
doesn't get pushed there.

Félix

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Hello,

Since, I cudn't get performance gain using llvm compiler, I've tried to
use
gold linker instead of going through these following steps.

a) 'llvm-gcc -c -flo -O2' to generate the .bc files.
b) 'llvm-ld' to combine them into a single .bc. No, not a .so nor a .a.
c) 'llc' to turn your combined .bc into a .s
d) 'as' to turn your .s into a .o

I followed instructions from web page. http://llvm.org/docs/GoldPlugin.html

I configured linker with these paramters.
../src/configure --host=i686-pc-linux-gpu --build=i686-pc-linux-gpu
--target=armv7fl-montavista-linux-gnueabi --enable-gold --enable-plugins
--enable-lto --with-cpu=cortex-a8 --with-interwork --with-arch=armv7-a
--with-mode=arm --with-tune=cortex-a8 --with-fpu=vfp3

Did a make then.

But the code generated with ld-new is intel binary and not a ARM binary :(

I did
arm_v7_vfp-le a.c
ld-new libs a.o -o binary
file ./binary
./binary: ELF 32-bit LSB executable, intel 80386 version 1(SYSV) dynamically
linked (uses shared libs), for GNU/Linux 2.6.9 not stripped

Any idea Why is it so ? Hoping for a quick reply

-Sanjeev

On Mon, Jun 28, 2010 at 2:23 PM, Anton Korobeynikov <anton at
korobeynikov.info
> wrote:
> > exactly
> Well, in general, there is no connection between the performance on
> x86 and on ARM.
> You can try to profile your code and find what causes the speedup on
> x86 and figure out the slowdowns on ARM.
>
> --
> With best regards, Anton Korobeynikov
> Faculty of Mathematics and Mechanics, Saint Petersburg State University
>
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Hello
> a) 'llvm-gcc -c -flo -O2' to generate the .bc files.
How llvm-gcc was configured & compiled?

With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University