[LLVMdev] llvm cross compilation and simplescalar simulation for ARM

[shiqiang]

I am sorry that I made a mistake in the last email: I choose llvm-3.4.2, not llvm-3.2.

> My best guess here would be you're including headers from your host
> platform (due to a misunderstood --sysroot), rather than the uclibc
> ones.

You are right here, I add a ‘-I’ option in clang command, and compile the application successfully:
clang -emit-llvm -I/my/toolchain/path/include -std=c89 —target=arm -O3 -c susan.c -o susan.c
llc -march=arm -filetype=asm susan.bc -o susan.s
arm-linux-gcc -static susan.s -lm -o susan.out

Yeah, simplescalar is too old to as a simulator in low power research. However, I cannot find another efficient simulator.
Fortunately, I make the whole environment work well so far. (I simply tested ’susan’ and ‘qsort’ in MiBench).

By the way, do u have any other suggestions to explorer low power options?(via LLVM and arm-gcc, and any other simulator & power model)
Thanks!

-Shiqiang


> 在 2015年5月7日，10:46，Tim Northover <t.p.northover at gmail.com> 写道：
> 
>> For this purpose, clang(3.2) + arm-gcc + simplescalar-arm(and panalyzer)
>> seems to be a good choice.
> 
> 3.2 is a very old release in LLVM terms. I doubt anyone here really
> knows all the details about it any more. You'd be much better off
> using the most recent stable release (3.6) or even trunk.
> 
>> but I encounter the problem about ‘uclibc’. There is no ‘_IO_getc’ in libc.a of uclibc, but clang&llc compile ‘getc’ in C source to ‘_IO_getc’ in assembler.
> 
> The current source doesn't seem to randomly create calls to _IO_getc.
> My best guess here would be you're including headers from your host
> platform (due to a misunderstood --sysroot), rather than the uclibc
> ones.
> 
>> someone says OABI rather EABI is necessary if want the executable run on simplescalar. So I don’t know how to solve this issue.
> 
> This is really worrying too: no-one uses OABI any more. It's virtually
> untested on linux, as far as I know (though probably kept from
> complete bit-rot by the fact that iOS uses a similar ABI).
> 
>> However, I get a fatal error when I run susan.out on simplescalar-arm:
>> fatal: non-specultative fault (2) detected @ XXXXXXX
> 
> This could well happen if your simplescalar program isn't expecting
> gnueabi (or any eabi) code.
> 
>> arm-gcc-2.95.3 recommended by simplescalar-arm official
> 
> That's a massive red flag. GCC 2.95 was released in 1999 (2.95.3 in
> 2001). Those versions are truly ancient; they were obsolete before
> Clang was even a glint in Reid Spencer's eye (unfairly picking the
> first clang commit -- it's all Reid's fault, QED).
> 
>> 1. If I do compiler related low power experiment via llvm(3.2) + arm-gcc + simplescalar-arm(and panalyzer), how could I setup the environment?? Does anyone has  the experience and can give some instructions?
> 
> I suspect you're in for a world of pain. Both simplescalar and
> LLVM-3.2 appear to be too old to be viable these days, which means
> you're probably going to have to hack on one or both code-bases to
> have a hope of producing anything functional.
> 
> Tim.

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