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Message
From: brantley@m...
Date: Sun, 20 Apr 2003 06:44:32 -0100
Subject: Re: [openrisc] Problem with jump behavior
As often seems to happen, when I post a message I figure out what the
problem was. The problem had nothing to do with gcc or the simulation.
I did not have the memory clock set correctly. Once I changed that and
the jumps behaved properly.
Sorry about that,
Damon
----- Original Message -----
From: "Damon Brantley" <brantley@m... >
To: openrisc@o...
Date: Sat, 19 Apr 2003 23:18:36 -0500
Subject: [openrisc] Problem with jump behavior
>
>
> I am getting started with experimenting with openrisc. I pulled
> down and
> built the
> binutils and gcc for use with cygwin. I am using the ModelSim
> simulator
> that comes
> with the Xilinx WebPack.
>
> While experimenting with some very simple c programs, it looks
> like my
> jumps are off
> by one instruction.
>
> A test program I have been working with is:
> void main(){
> int i=0;
> while(1){
> i=i+1;
> }
> }
>
> The disassembly is
>
> 00010000 <_start>:
> 10000: 18 20 00 00 l.movhi r1,0x0
> 10004: a8 21 00 10 l.ori r1,r1,0x10
> 10008: 00 00 00 04 l.j 10018 <_main>
> 1000c: 15 00 00 00 l.nop 0x0
> 10010: 15 00 00 00 l.nop 0x0
> 10014: 03 ff ff fb l.j 10000 <_start>
>
> 00010018 <_main>:
> 10018: 9c 21 ff f8 l.addi r1,r1,0xfffffff8
> 1001c: d4 01 10 00 l.sw 0x0(r1),r2
> 10020: 9c 41 00 08 l.addi r2,r1,0x8
> 10024: 9c 60 00 00 l.addi r3,r0,0x0
> 10028: d7 e2 1f fc l.sw 0xfffffffc(r2),r3
> 1002c: 84 62 ff fc l.lwz r3,0xfffffffc(r2)
> 10030: 9c 63 00 01 l.addi r3,r3,0x1
> 10034: d7 e2 1f fc l.sw 0xfffffffc(r2),r3
> 10038: 03 ff ff fd l.j 1002c <_main+0x14>
> 1003c: 15 00 00 00 l.nop 0x0
> 10040: 84 41 00 00 l.lwz r2,0x0(r1)
> 10044: 44 00 48 00 l.jr r9
> 10048: 9c 21 00 08 l.addi r1,r1,0x8
>
>
> What I am seeing in the simulator is when a the jump at 10008 is
> executed,
> instead of seeing iwb_adr_o going to
> 10018, I am seeing it go to 1001c.
>
> In this case the program simulates as expected, but when I add
> function
> calls the test programs fail because
> the first instruction is missed, which is usually setting up a
> stack frame.
>
> This is what I am using for building my test program:
>
> /opt/or32-uclinux/bin/or32-uclinux-gcc -g -Wa,-a=crt0.asm -c -o
> crt0.or32
> crt0.S
> /opt/or32-uclinux/bin/or32-uclinux-gcc -g -Wa,-a=test1.asm -c -o
> test1.or32 test1.c
> /opt/or32-uclinux/bin/or32-uclinux-ld -Ttext 10000 -Tdata 20 -o
> test1.bin
> crt0.or32 test1.or32
>
> Am I missing a compile or link flag or is model sim possibly doing
> the
> simulation wrong.
>
> Thanks,
> Damon
>
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