GCC generates incorrect code for the following C code in both ARM and Thumb
modes. The initialisation of param[0] is performed in the wrong leg of the if()
statement, consequently the assignemnt to DMA_ADDR_REG uses an uninitialised
value. Command line, compiler specs and object dump are included below.
I quickly tested 4.1.2 and 4.2.0 and they exhibit the same problem.
#define DMA_ADDR_REG (*(unsigned volatile *) 0xffff1000)
extern void panic(void);
static void inner_func(void *data, unsigned size)
{
if (!size)
panic();
else
DMA_ADDR_REG = (unsigned long) data;
}
void outer_func(unsigned offset, unsigned size)
{
unsigned char param[1];
param[0] = offset;
inner_func(param, size);
}
/*
* gcc -Wall -O2 -fno-strict-aliasing
*
bug.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <outer_func>:
0: b500 push {lr}
2: b081 sub sp, #4
4: 2900 cmp r1, #0
6: d005 beq.n 14 <outer_func+0x14>
8: 466a mov r2, sp
a: 4b05 ldr r3, [pc, #20] (20 <.text+0x20>)
c: 3203 adds r2, #3
e: 601a str r2, [r3, #0]
10: b001 add sp, #4
12: bd00 pop {pc}
14: 466b mov r3, sp
16: 3303 adds r3, #3
18: 7018 strb r0, [r3, #0]
1a: f7ff fffe bl 0 <panic>
1e: e7f7 b.n 10 <panic+0x10>
20: 1000 asrs r0, r0, #32
22: Address 0x00000022 is out of bounds.
*
* gcc -Wall -O2 -fno-strict-aliasing -mthumb
*
bug.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <outer_func>:
0: e52de004 str lr, [sp, #-4]!
4: e3510000 cmp r1, #0 ; 0x0
8: e24dd004 sub sp, sp, #4 ; 0x4
c: 128d2003 addne r2, sp, #3 ; 0x3
10: 13e03a0e mvnne r3, #57344 ; 0xe000
14: 15032fff strne r2, [r3, #-4095]
18: 0a000001 beq 24 <outer_func+0x24>
1c: e28dd004 add sp, sp, #4 ; 0x4
20: e8bd8000 ldmia sp!, {pc}
24: e5cd0003 strb r0, [sp, #3]
28: ebfffffe bl 0 <panic>
2c: eafffffa b 1c <panic+0x1c>
*
* gcc -v
*
Using built-in specs.
Target: arm-unknown-elf
Configured with: ../configure --target=arm-unknown-elf --prefix=/usr
--disable-nls --disable-shared --disable-threads --with-gnu-as --with-gnu-ld
--enable-multilib --disable-win32-registry --enable-sjlj-exceptions
--with-newlib --enable-__cxa_exit --enable-languages=c
--with-gxx-include-dir=/usr/arm-unknown-elf/include/c++
Thread model: single
gcc version 4.2.2
*/
--
Summary: gcc-4.2.2 generates bad code on ARM
Product: gcc
Version: 4.2.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: zero at colonel-panic dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: arm-unknown-elf
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33949
