http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49521
Summary: [arm] Bad PIC register load in for static initializers
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: rmansfi...@qnx.com
Host: x86_64-linux-gnu
Target: arm-unknown-linux-gnu
Build: x86_64-linux-gnu
$ ./xgcc -v
../configure --target=arm-unknown-linux-gnu
--prefix=/home/ryan/x-tools/arm-unknown-linux-gnu
--with-headers=/home/ryan/x-tools/arm-unknown-linux-gnu/arm-unknown-linux-gnu/include
--with-local-prefix=/home/ryan/x-tools/arm-unknown-linux-gnu/arm-unknown-linux-gnu
--disable-nls --enable-threads=posix --enable-symvers=gnu --enable-__cxa_atexit
--enable-languages=c++ --enable-shared --enable-c99 --enable-long-long
Thread model: posix
gcc version 4.6.1 20110518 (prerelease) [gcc-4_6-branch revision 173875] (GCC)
Yes, this only happens with the old ABI but this wrong-code seems to happens
very frequently.
$ ./xgcc -B. -fpic -O2 ~/t.ii -S
_GLOBAL__sub_I_t.ii:
@ args = 0, pretend = 0, frame = 116
@ frame_needed = 1, uses_anonymous_args = 0
stmfd sp!, {fp, lr}
ldr r1, .L1064 <- load GOT offset
add fp, sp, #4
sub sp, sp, #116
mov r0, #0
ldr r1, [r0, r1] <- crash
<snip>
.L1064:
.word __gxx_personality_sj0(GOT)
(note 2 354 264 NOTE_INSN_FUNCTION_BEG)
(insn 264 2 287 (set (reg:SI 2 r2)
(const_int 0 [0])) 168 {*arm_movsi_insn}
(expr_list:REG_EQUAL (const_int 0 [0])
(nil)))
(insn 287 264 288 (set (reg:SI 3 r3 [275])
(unspec:SI [
(mem:SI (label_ref 364) [0 S4 A32])
] 3)) 170 {pic_load_addr_32bit}
(expr_list:REG_EQUIV (unspec:SI [
(symbol_ref:SI ("__gxx_personality_sj0") [flags 0x41])
] 3)
(nil)))
(insn 288 287 229 (set (reg/f:SI 3 r3 [256])
(mem:SI (plus:SI (reg:SI 2 r2)
(reg:SI 3 r3 [275])) [0 S4 A32])) 168 {*arm_movsi_insn}
(expr_list:REG_DEAD (reg:SI 2 r2)
(expr_list:REG_EQUIV (symbol_ref:SI ("__gxx_personality_sj0") [flags
0x41])
(nil))))
(insn 229 288 230 (set (mem/c:SI (plus:SI (reg/f:SI 11 fp)
(const_int -32 [0xffffffffffffffe0])) [0 S4 A32])
(reg/f:SI 3 r3 [256])) 168 {*arm_movsi_insn}
(expr_list:REG_DEAD (reg/f:SI 3 r3 [256])
(nil)))
If I explicitly specify a PIC register (e.g. -mpic-register=4), the load is
sane.
e.g.
_GLOBAL__sub_I_t.ii:
@ args = 0, pretend = 0, frame = 112
@ frame_needed = 1, uses_anonymous_args = 0
stmfd sp!, {r4, fp, lr}
ldr r4, .L1064
add fp, sp, #8
ldr r2, .L1064+4
sub sp, sp, #112
ldr r1, .L1064+8
ldr r0, .L1064+12
.LPIC227:
add r4, pc, r4
ldr r3, .L1064+16
ldr r1, [r4, r1]
<snip>
.L1064:
.word _GLOBAL_OFFSET_TABLE_-(.LPIC227+8)
.word .LLSDA1449-(.LPIC224+8)
.word __gxx_personality_sj0(GOT)
