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EEGCS-1.1.2 bug: handling signed bitfields on ARM processor
- To: egcs-bugs at egcs dot cygnus dot com
- Subject: EEGCS-1.1.2 bug: handling signed bitfields on ARM processor
- From: Stefan Sami-Soueiha <stefan_sami at gmx dot de>
- Date: Tue, 28 Sep 1999 14:33:57 +0200 (MEST)
Dear Sirs,
I have found a bug in the egcs-C-compiler, handling (signed) bitfields
for ARM processor architecture.
If a signed bitfield is not aligned to a byte boundary, and written with
a negative value, this is done by a word access and the instructions "mvn"
(e.g.:
ldr ip, [fp, #-16] !!! error ???
mvn ip, ip, asl #22 !!! this code sets all upper
mvn ip, ip, lsr #22 !!! bits too
str ip, [fp, #-16] !!! error ???
).
But these instructions sets all upper bits of this word too!
Example C-code: If in the structure "test_t" the bitfield "d" is set to
"-1",
the bits of the elements a,b,c are also set all "1".
I have appended the following:
1. the C-code generating the wrong assembler code output
2. the output of the program
3. cross compiler version, host OS version, and compiler call
4. the assembler output. The error lines are marked with "!!!"
Hope I give you all information you need.
best regards
Stefan
Sami-Soueiha
---------------------------------------------------------------------------
| Dipl.-Ing. Stefan Sami-Soueiha Tel.: +49 911 9673-0
|
| BinTec Communications AG Fax : +49 911 9673-1499
|
| Suedwestpark 94 http://www.bintec.de
|
| D-90449 Nuernberg/Germany email: sami@bintec.de
|
---------------------------------------------------------------------------
Appendix:
---------
1. C-code:
---------
void func()
{
typedef struct {
unsigned a:3;
unsigned b:5;
int c:6;
int d:8;
unsigned e:8;
} test_t;
test_t test;
memset(&test, 0 , sizeof(test));
test.a = 1;
printf("1.a-e: %d %d %d %d %d\n",test.a,test.b,test.c,test.d,test.e);
test.b = 2;
printf("2.a-e: %d %d %d %d %d\n",test.a,test.b,test.c,test.d,test.e);
test.c = 3;
printf("3.a-e: %d %d %d %d %d\n",test.a,test.b,test.c,test.d,test.e);
test.d = -1;
printf("4.a-e: %d %d %d %d %d\n",test.a,test.b,test.c,test.d,test.e);
test.e = 5;
printf("5.a-e: %d %d %d %d %d\n",test.a,test.b,test.c,test.d,test.e);
}
2. Output:
-----------
1.a-e: 1 0 0 0 0
2.a-e: 1 2 0 0 0
3.a-e: 1 2 3 0 0
4.a-e: 7 31 63 255 0
5.a-e: 7 31 63 255 5
3. Compiler version/call:
-------------------------
%uname -a
SunOS junior 5.6 Generic_105181-14 sun4u sparc SUNW,Ultra-4
install-configure:
./configure --with-gnu-as --with-gnu-ld --target=arm-aout
--prefix=/local/bin.SOLARIS_ARM
--exec-prefix=/local/bin.SOLARIS_ARM --bindir=/local/bin.SOLARIS_ARM
%arm-aout-gcc -v
Reading specs from
/local/bin.SOLARIS_ARM/lib/gcc-lib/arm-aout/egcs-2.91.66/specs
gcc version egcs-2.91.66 19990314 (egcs-1.1.2 release)
%arm-aout-gcc -nostdinc -fno-builtin -fsigned-char -mbig-endian -mapcs-32
-Wa,-EB -mcpu=arm7tdmi
-Wall -g -O -O2 -S -o ex2.a4_s ex2.c
4. Assembler-file:
-------------------
rfp .req r9
sl .req r10
fp .req r11
ip .req r12
sp .req r13
lr .req r14
pc .req r15
gcc2_compiled.:
___gnu_compiled_c:
.stabs "/bintec/bibo/usr/stefans/src/example/app/",100,0,0,Ltext0
.stabs "ex2.c",100,0,315,Ltext0
.text
Ltext0:
.stabs "int:t1=r1;0020000000000;0017777777777;",128,0,0,0
.stabs "char:t2=r2;0;127;",128,0,0,0
.stabs "long int:t3=r1;0020000000000;0017777777777;",128,0,0,0
.stabs "unsigned int:t4=r1;0000000000000;0037777777777;",128,0,0,0
.stabs "long unsigned int:t5=r1;0000000000000;0037777777777;",128,0,0,0
.stabs "long long
int:t6=r1;01000000000000000000000;0777777777777777777777;",128,0,0,0
.stabs "long long unsigned
int:t7=r1;0000000000000;01777777777777777777777;",128,0,0,0
.stabs "short int:t8=r8;-32768;32767;",128,0,0,0
.stabs "short unsigned int:t9=r9;0;65535;",128,0,0,0
.stabs "signed char:t10=r10;-128;127;",128,0,0,0
.stabs "unsigned char:t11=r11;0;255;",128,0,0,0
.stabs "float:t12=r1;4;0;",128,0,0,0
.stabs "double:t13=r1;8;0;",128,0,0,0
.stabs "long double:t14=r1;8;0;",128,0,0,0
.stabs "complex int:t15=s8real:1,0,32;imag:1,32,32;;",128,0,0,0
.stabs "complex float:t16=r16;4;0;",128,0,0,0
.stabs "complex double:t17=r17;8;0;",128,0,0,0
.stabs "complex long double:t18=r18;8;0;",128,0,0,0
.stabs "void:t19=19",128,0,0,0
.stabs
"test_t:t20=21=s4a:4,0,3;b:4,3,5;c:1,8,6;d:1,14,8;e:4,22,8;;",128,0,10,0
.align 0
LC0:
.ascii "1.a-e: %d %d %d %d %d\012\000"
.align 0
LC1:
.ascii "2.a-e: %d %d %d %d %d\012\000"
.align 0
LC2:
.ascii "3.a-e: %d %d %d %d %d\012\000"
.align 0
LC3:
.ascii "4.a-e: %d %d %d %d %d\012\000"
.align 0
LC4:
.ascii "5.a-e: %d %d %d %d %d\012\000"
.align 0
.global _func
_func:
.stabd 68,0,3
@ args = 0, pretend = 0, frame = 4
@ frame_needed = 1, current_function_anonymous_args = 0
LBB2:
mov ip, sp
stmfd sp!, {fp, ip, lr, pc}
.stabd 68,0,13
mov r1, #0
mov r2, #4
.stabd 68,0,3
sub sp, sp, #12
sub fp, ip, #4
.stabd 68,0,13
sub r0, fp, #16
bl _memset
.stabd 68,0,15
ldr r2, [fp, #-16]
bic r2, r2, #-1073741824
orr r2, r2, #536870912
str r2, [fp, #-16]
.stabd 68,0,16
mov r3, r2, asl #14
mov r3, r3, asr #24
str r3, [sp, #0]
ldrh r2, [fp, #-14] @ movhi
mov r2, r2, lsr #2
and r2, r2, #255
str r2, [sp, #4]
ldr r0, L2
ldrb r3, [fp, #-15]
ldrb r1, [fp, #-16] @ zero_extendqisi2
mov r3, r3, asl #24
mov r3, r3, asr #26
mov r2, r1
mov r1, r1, lsr #5
and r2, r2, #31
bl _printf
.stabd 68,0,17
ldr r2, [fp, #-16]
bic r2, r2, #486539264
orr r2, r2, #33554432
str r2, [fp, #-16]
.stabd 68,0,18
mov r3, r2, asl #14
mov r3, r3, asr #24
str r3, [sp, #0]
ldrh r2, [fp, #-14] @ movhi
mov r2, r2, lsr #2
and r2, r2, #255
str r2, [sp, #4]
ldr r0, L2+4
ldrb r3, [fp, #-15]
ldrb r1, [fp, #-16] @ zero_extendqisi2
mov r3, r3, asl #24
mov r3, r3, asr #26
mov r2, r1
mov r1, r1, lsr #5
and r2, r2, #31
bl _printf
.stabd 68,0,19
ldr r2, [fp, #-16]
bic r2, r2, #15728640
orr r2, r2, #786432
str r2, [fp, #-16]
.stabd 68,0,20
mov r3, r2, asl #14
mov r3, r3, asr #24
str r3, [sp, #0]
ldrh r2, [fp, #-14] @ movhi
mov r2, r2, lsr #2
and r2, r2, #255
str r2, [sp, #4]
ldr r0, L2+8
ldrb r3, [fp, #-15]
ldrb r1, [fp, #-16] @ zero_extendqisi2
mov r3, r3, asl #24
mov r3, r3, asr #26
mov r2, r1
mov r1, r1, lsr #5
and r2, r2, #31
bl _printf
.stabd 68,0,21
ldr ip, [fp, #-16] !!! error ???
mvn ip, ip, asl #22 !!! this code sets all upper
mvn ip, ip, lsr #22 !!! bits too
str ip, [fp, #-16] !!! error ???
.stabd 68,0,22
mov ip, ip, asl #14
mov ip, ip, asr #24
str ip, [sp, #0]
ldrh r3, [fp, #-14] @ movhi
mov r3, r3, lsr #2
and r3, r3, #255
str r3, [sp, #4]
ldr r0, L2+12
ldrb r3, [fp, #-15]
ldrb r1, [fp, #-16] @ zero_extendqisi2
mov r3, r3, asl #24
mov r3, r3, asr #26
mov r2, r1
mov r1, r1, lsr #5
and r2, r2, #31
bl _printf
.stabd 68,0,23
ldr r2, [fp, #-16]
bic r2, r2, #1000
orr r2, r2, #20
str r2, [fp, #-16]
.stabd 68,0,24
mov r3, r2, asl #14
mov r3, r3, asr #24
str r3, [sp, #0]
ldrh r2, [fp, #-14] @ movhi
mov r2, r2, lsr #2
and r2, r2, #255
str r2, [sp, #4]
ldr r0, L2+16
ldrb r3, [fp, #-15]
ldrb r1, [fp, #-16] @ zero_extendqisi2
mov r3, r3, asl #24
mov r3, r3, asr #26
mov r2, r1
mov r1, r1, lsr #5
and r2, r2, #31
bl _printf
.stabd 68,0,25
LBE2:
ldmea fp, {fp, sp, pc}
L3:
.align 0
L2:
.word LC0
.word LC1
.word LC2
.word LC3
.word LC4
.stabs "func:F19",36,0,3,_func
.stabs "test:20",128,0,12,-16
.stabn 192,0,0,LBB2
.stabn 224,0,0,LBE2
END.
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