llvm dev - Mar 2008 - [LLVMdev] llvm-gcc and mips

Hi,

When using mips-unknown-linux-gnu as a cross-compiler, the llvm Mips
backend is called by cc1 and with that you get llvm bytecode defined
relative to the Mips ABI. This can be messing up somehow your
generated C code.

2008/3/7, HyperQuantum <hyperquantum at
gmail.com>:
> On Fri, Feb 29, 2008 at 2:23 PM, HyperQuantum <hyperquantum at
gmail.com> wrote:
>  >  At least I got llvm-gcc running again.
>
>
> Something is still wrong because I cannot get Pi_Calc to run after
>  compiling it with this semi-cross-compiler, and it worked with the
>  regular llvm-gcc. I configured the cross compiler with target
>  mips-unknown-linux-gnu. Should I use another triple or do I need to
>  hack the llvm-gcc sources some more?
>
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>

-- 
Bruno Cardoso Lopes
http://www.brunocardoso.org

"Morte: Mas não para você pistoleiro"

On Fri, Mar 7, 2008 at 8:28 PM, Bruno Cardoso Lopes
<bruno.cardoso at gmail.com> wrote:
>  When using mips-unknown-linux-gnu as a cross-compiler, the llvm Mips
>  backend is called by cc1 and with that you get llvm bytecode defined
>  relative to the Mips ABI.
That was my intention. The PSP has a 32-bit MIPS (derived) CPU. What I
don't know is if that triple is the right one to pick.
I looked through the patch that turns gcc into psp-gcc and it defines
a special triple called simply "psp":

diff -burN gcc-4.1.0/config.sub gcc-psp/config.sub
--- gcc-4.1.0/config.sub	2005-12-16 12:57:40.000000000 +0000
+++ gcc-psp/config.sub	2006-05-07 13:27:40.000000000 +0100
@@ -264,6 +264,7 @@
 	| mipsisa64sb1 | mipsisa64sb1el \
 	| mipsisa64sr71k | mipsisa64sr71kel \
 	| mipstx39 | mipstx39el \
+	| mipsallegrex | mipsallegrexel \
 	| mn10200 | mn10300 \
 	| mt \
 	| msp430 \
@@ -346,6 +347,7 @@
 	| mipsisa64sb1-* | mipsisa64sb1el-* \
 	| mipsisa64sr71k-* | mipsisa64sr71kel-* \
 	| mipstx39-* | mipstx39el-* \
+	| mipsallegrex-* | mipsallegrexel-* \
 	| mmix-* \
 	| mt-* \
 	| msp430-* \
@@ -689,6 +691,10 @@
 		basic_machine=m68k-atari
 		os=-mint
 		;;
+	psp)
+		basic_machine=mipsallegrexel-psp
+		os=-elf
+		;;
 	mips3*-*)
 		basic_machine=`echo $basic_machine | sed -e 's/mips3/mips64/'`
 		;;

I did not see any changes in the rest of the diff that did something
to the ABI; as far as I understand it it's only adding some extra
instructions. So I assume that the PSP uses a standard MIPS ABI. And
yet something is still wrong, even more than with a native
"i686-pc-linux-gnu" llvm-gcc.
>  This can be messing up somehow your
>  generated C code.
Supposed that you knew my approach was intentional (correct me if I'm
wrong), what problem did you see here?


Regards,
Kevin André

Hi Kevin,
>  Supposed that you knew my approach was intentional (correct me if I'm
>  wrong), what problem did you see here?
Yes, i'm trying to help raising possible problems. For example, there are
Mips machines with different endianess, the llvm Mips default (Big) is
different from
the psp toochain default one (correct me if I'm wrong - Little), maybe
this is messing
up...

Cheers,

-- 
Bruno Cardoso Lopes
http://www.brunocardoso.org

"Morte: Mas não para você pistoleiro"