inline-asm/10035: arm register r0 is corrupted

[murphychen@mail2000.com.tw]

>Number:         10035
>Category:       inline-asm
>Synopsis:       arm register r0 is corrupted
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Mar 12 06:36:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     gcc-3.0
>Release:        unknown-1.0
>Organization:
>Environment:
linux
>Description:
When assigning local variable to use arm register r0, the initialization of the local variable will be ignored.
>How-To-Repeat:
compile the c code again.
>Fix:
Don't know how to fix.
>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="gccbug.txt"
Content-Disposition: inline; filename="gccbug.txt"

$cat test.c

int fun(char *s, long n) {
  register long a asm("r0");
  a = 3;
  fun("xxx", a);
  a = 5;
  return a;
}

$ arm-linux-gcc -Os -S -mthumb -mcpu=arm7tdmi -mtune=arm7tdmi -march=armv4t test.c 

$ cat test.s

@ Generated by gcc 3.0 for ARM/elf
        .file   "test.c"
        .code   16
        .section        .rodata
        .align  2
.LC0:
        .ascii  "xxx\000"
        .text
        .align  2
        .global fun
        .thumb_func
        .type   fun,function
fun:
        push    {lr}
        ldr     r0, .L3
        mov     r1, r0
        bl      fun
        mov     r0, #5
        pop     {pc}
.L4:
        .align  2
.L3:
        .word   .LC0
.Lfe1:
        .size   fun,.Lfe1-fun
        .ident  "GCC: (GNU) 3.0"

$ arm-linux-gcc -v -Os -S -mthumb -mcpu=arm7tdmi -mtune=arm7tdmi -march=armv4t test.c 
Reading specs from /usr/local/arm/3.0/lib/gcc-lib/arm-linux/3.0/specs
Configured with: ../../src/gcc-3.0/configure --target=arm-linux --prefix=/usr/local/arm/3.0 --enable-languages=c,c++,objc,f77,java --enable-threads
Thread model: posix
gcc version 3.0
 /usr/local/arm/3.0/lib/gcc-lib/arm-linux/3.0/cc1 -lang-c -v -D__GNUC__=3 -D__GNUC_MINOR__=0 -D__GNUC_PATCHLEVEL__=0 -Dunix -Dlinux -D__ELF__ -D__unix__ -D__linux__ -D__ELF__ -D__unix -D__linux -Asystem=unix -Asystem=posix -Acpu=arm -Amachine=arm -D__CHAR_UNSIGNED__ -D__OPTIMIZE_SIZE__ -D__OPTIMIZE__ -D__STDC_HOSTED__=1 -D__ARM_ARCH_4T__ -D__APCS_32__ -D__ARMEL__ -D__THUMBEL__ -D__thumb__ test.c -quiet -dumpbase test.c -mthumb -mcpu=arm7tdmi -mtune=arm7tdmi -march=armv4t -Os -version -o test.s
GNU CPP version 3.0 (cpplib) (ARM GNU/Linux with ELF)
GNU C version 3.0 (arm-linux)
        compiled by GNU C version 2.95.2 20000220 (Debian GNU/Linux).
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/arm/3.0/lib/gcc-lib/arm-linux/3.0/include
 /usr/local/arm/3.0/arm-linux/sys-include
 /usr/local/arm/3.0/arm-linux/include
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