https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66239
Bug ID: 66239
Summary: Unoptimized sqrt(float or double) returns wrong values
for ARM Cortex-A8 -mfloat-abi=[soft,softfp]
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: maciej.andrzejewski at data dot pl
Target Milestone: ---
Tested both on GCC 4.9.1 (compiled toolchain using crosstool-ng) and 4.9.2
(compiled toolchain using buildroot).
Simple code:
-- CODE --
#include <stdio.h>
#include <cmath>
#include <math.h>
int main( void )
{
double sq3 = 9.1;
double ret3 = sqrtf(sq3);
printf("%f\n", ret3);
float sq4 = 9.1;
double ret4 = sqrtf(sq4);
printf("%f\n", ret4);
double sq1 = 9.1;
double ret1 = sqrt(sq1);
printf("%f\n", ret1);
float sq2 = 9.1;
double ret2 = sqrt(sq2);
printf("%f\n", ret2);
return 0;
}
-- CODE --
compiled with command:
g++ -mcpu=cortex-a8 -march=armv7-a -mtune=cortex-a8 -mfpu=neon
-mthumb-interwork -mfpu=neon -Wall -Wextra -mfloat-abi=softfp
or
g++ -mcpu=cortex-a8 -march=armv7-a -mtune=cortex-a8 -mfpu=neon
-mthumb-interwork -mfpu=neon -Wall -Wextra -mfloat-abi=soft
prints output when run:
-- OUTPUT --
0.000000
0.000000
89884613882771507935772421602449274280826426490922860415370742828850803088708436568909338933268615382725731836148779976703521876921396883553861971381426763394584730974161643341227168116324626810241973964225774272233175406843466371141886318608237834273423597057507238373804952327520531541920130815989439791104.000000
89884613882771507935772421602449274280826426490922860415370742828850803088708436568909338933268615382725731836148779976703521876921396883553861971381426763394584730974161643341227168116324626810241973964225774272233175406843466371141886318608237834273423597057507238373804952327520531541920130815989439791104.000000
-- OUTPUT --
when compiled with added ANY optimization flag (O, O1, O2, O3, Og) prints
proper output:
-- OUTPUT 2 --
3.016621
3.016621
3.016621
3.016621
-- OUTPUT 2 --
*** Additional info ***
g++ --version:
arm-none-linux-gnueabi-g++ (Buildroot 2015.02) 4.9.2
readelf -a a.out:
-- READELF --
macieja@ubuntu:~/Projects/sqrtf$ readelf -a a.out
ELF Header:
Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: ARM
Version: 0x1
Entry point address: 0x103d0
Start of program headers: 52 (bytes into file)
Start of section headers: 5012 (bytes into file)
Flags: 0x5000202, has entry point, Version5 EABI,
soft-float ABI
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 8
Size of section headers: 40 (bytes)
Number of section headers: 29
Section header string table index: 26
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf
Al
[ 0] NULL 00000000 000000 000000 00 0 0
0
[ 1] .interp PROGBITS 00010134 000134 000013 00 A 0 0
1
[ 2] .note.ABI-tag NOTE 00010148 000148 000020 00 A 0 0
4
[ 3] .hash HASH 00010168 000168 000038 04 A 4 0
4
[ 4] .dynsym DYNSYM 000101a0 0001a0 000090 10 A 5 1
4
[ 5] .dynstr STRTAB 00010230 000230 0000d3 00 A 0 0
1
[ 6] .gnu.version VERSYM 00010304 000304 000012 02 A 4 0
2
[ 7] .gnu.version_r VERNEED 00010318 000318 000040 00 A 5 2
4
[ 8] .rel.dyn REL 00010358 000358 000008 08 A 4 0
4
[ 9] .rel.plt REL 00010360 000360 000020 08 AI 4 11
4
[10] .init PROGBITS 00010380 000380 00000c 00 AX 0 0
4
[11] .plt PROGBITS 0001038c 00038c 000044 04 AX 0 0
4
[12] .text PROGBITS 000103d0 0003d0 0001f8 00 AX 0 0
4
[13] .fini PROGBITS 000105c8 0005c8 000008 00 AX 0 0
4
[14] .rodata PROGBITS 000105d0 0005d0 000008 00 A 0 0
4
[15] .ARM.exidx ARM_EXIDX 000105d8 0005d8 000018 00 AL 12 0
4
[16] .eh_frame PROGBITS 000105f0 0005f0 000004 00 A 0 0
4
[17] .init_array INIT_ARRAY 000205f4 0005f4 000004 00 WA 0 0
4
[18] .fini_array FINI_ARRAY 000205f8 0005f8 000004 00 WA 0 0
4
[19] .jcr PROGBITS 000205fc 0005fc 000004 00 WA 0 0
4
[20] .dynamic DYNAMIC 00020600 000600 000100 08 WA 5 0
4
[21] .got PROGBITS 00020700 000700 000020 04 WA 0 0
4
[22] .data PROGBITS 00020720 000720 000008 00 WA 0 0
4
[23] .bss NOBITS 00020728 000728 000004 00 WA 0 0
1
[24] .comment PROGBITS 00000000 000728 00001f 01 MS 0 0
1
[25] .ARM.attributes ARM_ATTRIBUTES 00000000 000747 000037 00 0 0
1
[26] .shstrtab STRTAB 00000000 00077e 0000f3 00 0 0
1
[27] .symtab SYMTAB 00000000 000874 000700 10 28 86
4
[28] .strtab STRTAB 00000000 000f74 00041e 00 0 0
1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
There are no section groups in this file.
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x0005d8 0x000105d8 0x000105d8 0x00018 0x00018 R 0x4
PHDR 0x000034 0x00010034 0x00010034 0x00100 0x00100 R E 0x4
INTERP 0x000134 0x00010134 0x00010134 0x00013 0x00013 R 0x1
[Requesting program interpreter: /lib/ld-linux.so.3]
LOAD 0x000000 0x00010000 0x00010000 0x005f4 0x005f4 R E 0x10000
LOAD 0x0005f4 0x000205f4 0x000205f4 0x00134 0x00138 RW 0x10000
DYNAMIC 0x000600 0x00020600 0x00020600 0x00100 0x00100 RW 0x4
NOTE 0x000148 0x00010148 0x00010148 0x00020 0x00020 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x10
Section to Segment mapping:
Segment Sections...
00 .ARM.exidx
01
02 .interp
03 .interp .note.ABI-tag .hash .dynsym .dynstr .gnu.version
.gnu.version_r .rel.dyn .rel.plt .init .plt .text .fini .rodata .ARM.exidx
.eh_frame
04 .init_array .fini_array .jcr .dynamic .got .data .bss
05 .dynamic
06 .note.ABI-tag
07
Dynamic section at offset 0x600 contains 27 entries:
Tag Type Name/Value
0x00000001 (NEEDED) Shared library: [libstdc++.so.6]
0x00000001 (NEEDED) Shared library: [libm.so.6]
0x00000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x00000001 (NEEDED) Shared library: [libc.so.6]
0x0000000c (INIT) 0x10380
0x0000000d (FINI) 0x105c8
0x00000019 (INIT_ARRAY) 0x205f4
0x0000001b (INIT_ARRAYSZ) 4 (bytes)
0x0000001a (FINI_ARRAY) 0x205f8
0x0000001c (FINI_ARRAYSZ) 4 (bytes)
0x00000004 (HASH) 0x10168
0x00000005 (STRTAB) 0x10230
0x00000006 (SYMTAB) 0x101a0
0x0000000a (STRSZ) 211 (bytes)
0x0000000b (SYMENT) 16 (bytes)
0x00000015 (DEBUG) 0x0
0x00000003 (PLTGOT) 0x20700
0x00000002 (PLTRELSZ) 32 (bytes)
0x00000014 (PLTREL) REL
0x00000017 (JMPREL) 0x10360
0x00000011 (REL) 0x10358
0x00000012 (RELSZ) 8 (bytes)
0x00000013 (RELENT) 8 (bytes)
0x6ffffffe (VERNEED) 0x10318
0x6fffffff (VERNEEDNUM) 2
0x6ffffff0 (VERSYM) 0x10304
0x00000000 (NULL) 0x0
Relocation section '.rel.dyn' at offset 0x358 contains 1 entries:
Offset Info Type Sym.Value Sym. Name
0002071c 00000415 R_ARM_GLOB_DAT 00000000 __gmon_start__
Relocation section '.rel.plt' at offset 0x360 contains 4 entries:
Offset Info Type Sym.Value Sym. Name
0002070c 00000116 R_ARM_JUMP_SLOT 00000000 abort
00020710 00000216 R_ARM_JUMP_SLOT 00000000 __libc_start_main
00020714 00000416 R_ARM_JUMP_SLOT 00000000 __gmon_start__
00020718 00000816 R_ARM_JUMP_SLOT 00000000 printf
Unwind table index '.ARM.exidx' at offset 0x5d8 contains 3 entries:
0x103d0 <_start>: 0x1 [cantunwind]
0x104f4 <main>: 0x80840db0
Compact model index: 0
0x84 0x0d pop {r4, r6, r7, r14}
0xb0 finish
0x10564 <__libc_csu_init>: 0x1 [cantunwind]
Symbol table '.dynsym' contains 9 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
1: 00000000 0 FUNC GLOBAL DEFAULT UND abort@GLIBC_2.4 (2)
2: 00000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.4
(2)
3: 00000000 0 FUNC GLOBAL DEFAULT UND
__aeabi_unwind_cpp_pr0@GCC_3.5 (3)
4: 00000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
5: 00000000 0 NOTYPE WEAK DEFAULT UND _Jv_RegisterClasses
6: 00000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
7: 00000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
8: 00000000 0 FUNC GLOBAL DEFAULT UND printf@GLIBC_2.4 (2)
Symbol table '.symtab' contains 112 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
1: 00010134 0 SECTION LOCAL DEFAULT 1
2: 00010148 0 SECTION LOCAL DEFAULT 2
3: 00010168 0 SECTION LOCAL DEFAULT 3
4: 000101a0 0 SECTION LOCAL DEFAULT 4
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9: 00010360 0 SECTION LOCAL DEFAULT 9
10: 00010380 0 SECTION LOCAL DEFAULT 10
11: 0001038c 0 SECTION LOCAL DEFAULT 11
12: 000103d0 0 SECTION LOCAL DEFAULT 12
13: 000105c8 0 SECTION LOCAL DEFAULT 13
14: 000105d0 0 SECTION LOCAL DEFAULT 14
15: 000105d8 0 SECTION LOCAL DEFAULT 15
16: 000105f0 0 SECTION LOCAL DEFAULT 16
17: 000205f4 0 SECTION LOCAL DEFAULT 17
18: 000205f8 0 SECTION LOCAL DEFAULT 18
19: 000205fc 0 SECTION LOCAL DEFAULT 19
20: 00020600 0 SECTION LOCAL DEFAULT 20
21: 00020700 0 SECTION LOCAL DEFAULT 21
22: 00020720 0 SECTION LOCAL DEFAULT 22
23: 00020728 0 SECTION LOCAL DEFAULT 23
24: 00000000 0 SECTION LOCAL DEFAULT 24
25: 00000000 0 SECTION LOCAL DEFAULT 25
26: 00000000 0 FILE LOCAL DEFAULT ABS /home/macieja/Documents/b
27: 00010148 0 NOTYPE LOCAL DEFAULT 2 $d
28: 00000000 0 FILE LOCAL DEFAULT ABS /home/macieja/Documents/b
29: 000103d0 0 NOTYPE LOCAL DEFAULT 12 $a
30: 000105d8 0 NOTYPE LOCAL DEFAULT 15 $d
31: 00010400 0 NOTYPE LOCAL DEFAULT 12 $d
32: 00000000 0 FILE LOCAL DEFAULT ABS init.c
33: 000105d0 0 NOTYPE LOCAL DEFAULT 14 $d
34: 00020720 0 NOTYPE LOCAL DEFAULT 22 $d
35: 00000000 0 FILE LOCAL DEFAULT ABS /usr/local/buildroot_cort
36: 0001040c 0 NOTYPE LOCAL DEFAULT 12 $a
37: 0001040c 0 FUNC LOCAL DEFAULT 12 call_weak_fn
38: 00010428 0 NOTYPE LOCAL DEFAULT 12 $d
39: 00010380 0 NOTYPE LOCAL DEFAULT 10 $a
40: 000105c8 0 NOTYPE LOCAL DEFAULT 13 $a
41: 00000000 0 FILE LOCAL DEFAULT ABS /usr/local/buildroot_cort
42: 00010388 0 NOTYPE LOCAL DEFAULT 10 $a
43: 000105cc 0 NOTYPE LOCAL DEFAULT 13 $a
44: 00000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
45: 000205fc 0 OBJECT LOCAL DEFAULT 19 __JCR_LIST__
46: 00010430 0 NOTYPE LOCAL DEFAULT 12 $a
47: 00010430 0 FUNC LOCAL DEFAULT 12 deregister_tm_clones
48: 00010454 0 NOTYPE LOCAL DEFAULT 12 $d
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58: 000205f8 0 OBJECT LOCAL DEFAULT 18 __do_global_dtors_aux_fin
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60: 000104c0 0 FUNC LOCAL DEFAULT 12 frame_dummy
61: 000104ec 0 NOTYPE LOCAL DEFAULT 12 $d
62: 000205f4 0 NOTYPE LOCAL DEFAULT 17 $d
63: 000205f4 0 OBJECT LOCAL DEFAULT 17 __frame_dummy_init_array_
64: 00020728 0 NOTYPE LOCAL DEFAULT 23 $d
65: 00000000 0 FILE LOCAL DEFAULT ABS main.c
66: 000104f4 0 NOTYPE LOCAL DEFAULT 12 $a
67: 000105e0 0 NOTYPE LOCAL DEFAULT 15 $d
68: 000105d4 0 NOTYPE LOCAL DEFAULT 14 $d
69: 00000000 0 FILE LOCAL DEFAULT ABS elf-init.c
70: 00010564 0 NOTYPE LOCAL DEFAULT 12 $a
71: 000105bc 0 NOTYPE LOCAL DEFAULT 12 $d
72: 000105c4 0 NOTYPE LOCAL DEFAULT 12 $a
73: 00000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
74: 000105f0 0 NOTYPE LOCAL DEFAULT 16 $d
75: 000105f0 0 OBJECT LOCAL DEFAULT 16 __FRAME_END__
76: 000205fc 0 NOTYPE LOCAL DEFAULT 19 $d
77: 000205fc 0 OBJECT LOCAL DEFAULT 19 __JCR_END__
78: 00000000 0 FILE LOCAL DEFAULT ABS
79: 00020700 0 OBJECT LOCAL DEFAULT 21 _GLOBAL_OFFSET_TABLE_
80: 000205f8 0 NOTYPE LOCAL DEFAULT 17 __init_array_end
81: 000205f4 0 NOTYPE LOCAL DEFAULT 17 __init_array_start
82: 00020600 0 OBJECT LOCAL DEFAULT 20 _DYNAMIC
83: 0001038c 0 NOTYPE LOCAL DEFAULT 11 $a
84: 0001039c 0 NOTYPE LOCAL DEFAULT 11 $d
85: 000103a0 0 NOTYPE LOCAL DEFAULT 11 $a
86: 00020720 0 NOTYPE WEAK DEFAULT 22 data_start
87: 00000000 0 FUNC GLOBAL DEFAULT UND abort@@GLIBC_2.4
88: 000105c4 4 FUNC GLOBAL DEFAULT 12 __libc_csu_fini
89: 000103d0 0 FUNC GLOBAL DEFAULT 12 _start
90: 00000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@@GLIBC_
91: 00000000 0 FUNC GLOBAL DEFAULT UND __aeabi_unwind_cpp_pr0@@G
92: 00000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
93: 00000000 0 NOTYPE WEAK DEFAULT UND _Jv_RegisterClasses
94: 000105c8 0 FUNC GLOBAL DEFAULT 13 _fini
95: 00000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
96: 000105d0 4 OBJECT GLOBAL DEFAULT 14 _IO_stdin_used
97: 00000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
98: 00020720 0 NOTYPE GLOBAL DEFAULT 22 __data_start
99: 00020728 0 NOTYPE GLOBAL DEFAULT 23 __bss_start__
100: 00020728 0 OBJECT GLOBAL HIDDEN 22 __TMC_END__
101: 00020724 0 OBJECT GLOBAL HIDDEN 22 __dso_handle
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103: 00010564 96 FUNC GLOBAL DEFAULT 12 __libc_csu_init
104: 0002072c 0 NOTYPE GLOBAL DEFAULT 23 __bss_end__
105: 00000000 0 FUNC GLOBAL DEFAULT UND printf@@GLIBC_2.4
106: 00020728 0 NOTYPE GLOBAL DEFAULT 23 __bss_start
107: 0002072c 0 NOTYPE GLOBAL DEFAULT 23 _bss_end__
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Histogram for bucket list length (total of 3 buckets):
Length Number % of total Coverage
0 0 ( 0.0%)
1 0 ( 0.0%) 0.0%
2 2 ( 66.7%) 50.0%
3 0 ( 0.0%) 50.0%
4 1 ( 33.3%) 100.0%
Version symbols section '.gnu.version' contains 9 entries:
Addr: 0000000000010304 Offset: 0x000304 Link: 4 (.dynsym)
000: 0 (*local*) 2 (GLIBC_2.4) 2 (GLIBC_2.4) 3 (GCC_3.5)
004: 0 (*local*) 0 (*local*) 0 (*local*) 0 (*local*)
008: 2 (GLIBC_2.4)
Version needs section '.gnu.version_r' contains 2 entries:
Addr: 0x0000000000010318 Offset: 0x000318 Link: 5 (.dynstr)
000000: Version: 1 File: libgcc_s.so.1 Cnt: 1
0x0010: Name: GCC_3.5 Flags: none Version: 3
0x0020: Version: 1 File: libc.so.6 Cnt: 1
0x0030: Name: GLIBC_2.4 Flags: none Version: 2
Displaying notes found at file offset 0x00000148 with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 2.6.32
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-A8"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_rounding: Needed
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: int
Tag_CPU_unaligned_access: v6
Tag_Virtualization_use: TrustZone
-- READELF --
