this looks like a bug - arm target

Eric de Jong list_ericdejong_10@gmx.net
Thu Oct 9 08:09:00 GMT 2003


I stumbled across a code generation problem. I am still using gcc 3.3.0, so
maybe this is an old bug. Anyone care to verify this?

The problem is in the line  "strgtb r2, [r0, #2]":

 cmp r3, #7
 strgtb r2, [r0, #2]
 ble .L9

In the loop "for (r3=0; r3<8; r3++)" I expected "[r0,#2] = r2, but the condition
'gt' in 'strgtb' only stores the result when r3 > 7. It should be <=7. (Thus
strleb r2,[r0.#2] I think)

Eric.




---------------------
binutils 2.13.2.1
gcc 3.3.0
build under cygwin with
options --target=arm-ecos-elf --with-cpu=arm7tdmi --enable-languages=c,c++
---------------------

test.cpp
--------
typedef struct
{
   unsigned char data;
   unsigned char Reserved1;
   unsigned char control;
   unsigned char Reserved2;
   unsigned char tb;
   unsigned char Reserved3;
   unsigned short X;
} StructMMIO;

void test(void)
{
   int lus, lus2;
   StructMMIO* Mmio = (StructMMIO*)(0xC00000);

   while(1)
   for (lus=0; lus<8; lus++)
      Mmio->control = (1<<lus);
}
--------------------------------------------------------
arm-ecos-elf-gcc -O2 -S test.cpp

The result: test.s
----------------
 .file "test.cpp"
 .text
 .align 2
 .global _Z4testv
 .type _Z4testv, %function
_Z4testv:
 @ args = 0, pretend = 0, frame = 0
 @ frame_needed = 0, uses_anonymous_args = 0
 @ link register save eliminated.
 @ lr needed for prologue
 mov r0, #12582912
 mov r1, #1
.L10:
 mov r3, #0
.L9:
 mov r2, r1, asl r3
 add r3, r3, #1
 cmp r3, #7
 strgtb r2, [r0, #2]
 ble .L9
 b .L10
 .size _Z4testv, .-_Z4testv
 .ident "GCC: (GNU) 3.3"




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