[llvm-bugs] [Bug 51110] New: Emitted binary code changes when -g is enabled at -O3 with -flto
via llvm-bugs
llvm-bugs at lists.llvm.org
Thu Jul 15 14:42:55 PDT 2021
https://bugs.llvm.org/show_bug.cgi?id=51110
Bug ID: 51110
Summary: Emitted binary code changes when -g is enabled at -O3
with -flto
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Loop Optimizer
Assignee: unassignedbugs at nondot.org
Reporter: tlwang at uwaterloo.ca
CC: llvm-bugs at lists.llvm.org
The .text section for the following program (transformed_program.c) changes
after toggling the -g flag.
$ cat transformed_program0.c
int printf(const char *, ...);
long a[8];
long *b;
long c[7];
int(d)(int l) { return 0; }
int main() {
long *e = &c[6], *f = &a[2];
b = e;
int g = f != e, h = d(g);
*b = 7;
i:;
int k = h < 8;
if (!k)
goto j;
printf("%d\n", (int)a[h]);
h = h + 1;
goto i;
j:;
}
$
$ clang-trunk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
9cfec72ffeec242783b70e792c50bd163dcf9dbb)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/cnsun/usr/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ clang-trunk -flto -O3 -w transformed_program0.c ; objdump --disassemble a.out
> "no-g.txt"
$ clang-trunk -g -flto -O3 -w transformed_program0.c ; objdump --disassemble
a.out > "g.txt"
$ diff no-g.txt g.txt
40,41c40,41
< 401053: 49 c7 c0 20 12 40 00 mov $0x401220,%r8
< 40105a: 48 c7 c1 b0 11 40 00 mov $0x4011b0,%rcx
---
> 401053: 49 c7 c0 40 12 40 00 mov $0x401240,%r8
> 40105a: 48 c7 c1 d0 11 40 00 mov $0x4011d0,%rcx
113,144c113,136
< 401131: bf 04 20 40 00 mov $0x402004,%edi
< 401136: 31 f6 xor %esi,%esi
< 401138: 31 c0 xor %eax,%eax
< 40113a: e8 f1 fe ff ff callq 401030 <printf at plt>
< 40113f: bf 04 20 40 00 mov $0x402004,%edi
< 401144: 31 f6 xor %esi,%esi
< 401146: 31 c0 xor %eax,%eax
< 401148: e8 e3 fe ff ff callq 401030 <printf at plt>
< 40114d: bf 04 20 40 00 mov $0x402004,%edi
< 401152: 31 f6 xor %esi,%esi
< 401154: 31 c0 xor %eax,%eax
< 401156: e8 d5 fe ff ff callq 401030 <printf at plt>
< 40115b: bf 04 20 40 00 mov $0x402004,%edi
< 401160: 31 f6 xor %esi,%esi
< 401162: 31 c0 xor %eax,%eax
< 401164: e8 c7 fe ff ff callq 401030 <printf at plt>
< 401169: bf 04 20 40 00 mov $0x402004,%edi
< 40116e: 31 f6 xor %esi,%esi
< 401170: 31 c0 xor %eax,%eax
< 401172: e8 b9 fe ff ff callq 401030 <printf at plt>
< 401177: bf 04 20 40 00 mov $0x402004,%edi
< 40117c: 31 f6 xor %esi,%esi
< 40117e: 31 c0 xor %eax,%eax
< 401180: e8 ab fe ff ff callq 401030 <printf at plt>
< 401185: bf 04 20 40 00 mov $0x402004,%edi
< 40118a: 31 f6 xor %esi,%esi
< 40118c: 31 c0 xor %eax,%eax
< 40118e: e8 9d fe ff ff callq 401030 <printf at plt>
< 401193: bf 04 20 40 00 mov $0x402004,%edi
< 401198: 31 f6 xor %esi,%esi
< 40119a: 31 c0 xor %eax,%eax
< 40119c: e8 8f fe ff ff callq 401030 <printf at plt>
---
> 401131: 48 c7 05 34 2f 00 00 movq $0x7,0x2f34(%rip) # 404070 <c+0x30>
> 401138: 07 00 00 00
> 40113c: 8b 35 3e 2f 00 00 mov 0x2f3e(%rip),%esi # 404080 <a>
> 401142: bf 04 20 40 00 mov $0x402004,%edi
> 401147: 31 c0 xor %eax,%eax
> 401149: e8 e2 fe ff ff callq 401030 <printf at plt>
> 40114e: 8b 35 34 2f 00 00 mov 0x2f34(%rip),%esi # 404088 <a+0x8>
> 401154: bf 04 20 40 00 mov $0x402004,%edi
> 401159: 31 c0 xor %eax,%eax
> 40115b: e8 d0 fe ff ff callq 401030 <printf at plt>
> 401160: 8b 35 2a 2f 00 00 mov 0x2f2a(%rip),%esi # 404090 <a+0x10>
> 401166: bf 04 20 40 00 mov $0x402004,%edi
> 40116b: 31 c0 xor %eax,%eax
> 40116d: e8 be fe ff ff callq 401030 <printf at plt>
> 401172: 8b 35 20 2f 00 00 mov 0x2f20(%rip),%esi # 404098 <a+0x18>
> 401178: bf 04 20 40 00 mov $0x402004,%edi
> 40117d: 31 c0 xor %eax,%eax
> 40117f: e8 ac fe ff ff callq 401030 <printf at plt>
> 401184: 8b 35 16 2f 00 00 mov 0x2f16(%rip),%esi # 4040a0 <a+0x20>
> 40118a: bf 04 20 40 00 mov $0x402004,%edi
> 40118f: 31 c0 xor %eax,%eax
> 401191: e8 9a fe ff ff callq 401030 <printf at plt>
> 401196: 8b 35 0c 2f 00 00 mov 0x2f0c(%rip),%esi # 4040a8 <a+0x28>
> 40119c: bf 04 20 40 00 mov $0x402004,%edi
146,192c138,191
< 4011a3: 59 pop %rcx
< 4011a4: c3 retq
< 4011a5: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
< 4011ac: 00 00 00
< 4011af: 90 nop
<
< 00000000004011b0 <__libc_csu_init>:
< 4011b0: f3 0f 1e fa endbr64
< 4011b4: 41 57 push %r15
< 4011b6: 4c 8d 3d 53 2c 00 00 lea 0x2c53(%rip),%r15 #
403e10 <__frame_dummy_init_array_entry>
< 4011bd: 41 56 push %r14
< 4011bf: 49 89 d6 mov %rdx,%r14
< 4011c2: 41 55 push %r13
< 4011c4: 49 89 f5 mov %rsi,%r13
< 4011c7: 41 54 push %r12
< 4011c9: 41 89 fc mov %edi,%r12d
< 4011cc: 55 push %rbp
< 4011cd: 48 8d 2d 44 2c 00 00 lea 0x2c44(%rip),%rbp #
403e18 <__do_global_dtors_aux_fini_array_entry>
< 4011d4: 53 push %rbx
< 4011d5: 4c 29 fd sub %r15,%rbp
< 4011d8: 48 83 ec 08 sub $0x8,%rsp
< 4011dc: e8 1f fe ff ff callq 401000 <_init>
< 4011e1: 48 c1 fd 03 sar $0x3,%rbp
< 4011e5: 74 1f je 401206 <__libc_csu_init+0x56>
< 4011e7: 31 db xor %ebx,%ebx
< 4011e9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
< 4011f0: 4c 89 f2 mov %r14,%rdx
< 4011f3: 4c 89 ee mov %r13,%rsi
< 4011f6: 44 89 e7 mov %r12d,%edi
< 4011f9: 41 ff 14 df callq *(%r15,%rbx,8)
< 4011fd: 48 83 c3 01 add $0x1,%rbx
< 401201: 48 39 dd cmp %rbx,%rbp
< 401204: 75 ea jne 4011f0 <__libc_csu_init+0x40>
< 401206: 48 83 c4 08 add $0x8,%rsp
< 40120a: 5b pop %rbx
< 40120b: 5d pop %rbp
< 40120c: 41 5c pop %r12
< 40120e: 41 5d pop %r13
< 401210: 41 5e pop %r14
< 401212: 41 5f pop %r15
< 401214: c3 retq
< 401215: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
< 40121c: 00 00 00 00
<
< 0000000000401220 <__libc_csu_fini>:
< 401220: f3 0f 1e fa endbr64
< 401224: c3 retq
---
> 4011a3: e8 88 fe ff ff callq 401030 <printf at plt>
> 4011a8: 8b 35 02 2f 00 00 mov 0x2f02(%rip),%esi # 4040b0 <a+0x30>
> 4011ae: bf 04 20 40 00 mov $0x402004,%edi
> 4011b3: 31 c0 xor %eax,%eax
> 4011b5: e8 76 fe ff ff callq 401030 <printf at plt>
> 4011ba: 8b 35 f8 2e 00 00 mov 0x2ef8(%rip),%esi # 4040b8 <a+0x38>
> 4011c0: bf 04 20 40 00 mov $0x402004,%edi
> 4011c5: 31 c0 xor %eax,%eax
> 4011c7: e8 64 fe ff ff callq 401030 <printf at plt>
> 4011cc: 31 c0 xor %eax,%eax
> 4011ce: 59 pop %rcx
> 4011cf: c3 retq
>
> 00000000004011d0 <__libc_csu_init>:
> 4011d0: f3 0f 1e fa endbr64
> 4011d4: 41 57 push %r15
> 4011d6: 4c 8d 3d 33 2c 00 00 lea 0x2c33(%rip),%r15 # 403e10 <__frame_dummy_init_array_entry>
> 4011dd: 41 56 push %r14
> 4011df: 49 89 d6 mov %rdx,%r14
> 4011e2: 41 55 push %r13
> 4011e4: 49 89 f5 mov %rsi,%r13
> 4011e7: 41 54 push %r12
> 4011e9: 41 89 fc mov %edi,%r12d
> 4011ec: 55 push %rbp
> 4011ed: 48 8d 2d 24 2c 00 00 lea 0x2c24(%rip),%rbp # 403e18 <__do_global_dtors_aux_fini_array_entry>
> 4011f4: 53 push %rbx
> 4011f5: 4c 29 fd sub %r15,%rbp
> 4011f8: 48 83 ec 08 sub $0x8,%rsp
> 4011fc: e8 ff fd ff ff callq 401000 <_init>
> 401201: 48 c1 fd 03 sar $0x3,%rbp
> 401205: 74 1f je 401226 <__libc_csu_init+0x56>
> 401207: 31 db xor %ebx,%ebx
> 401209: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
> 401210: 4c 89 f2 mov %r14,%rdx
> 401213: 4c 89 ee mov %r13,%rsi
> 401216: 44 89 e7 mov %r12d,%edi
> 401219: 41 ff 14 df callq *(%r15,%rbx,8)
> 40121d: 48 83 c3 01 add $0x1,%rbx
> 401221: 48 39 dd cmp %rbx,%rbp
> 401224: 75 ea jne 401210 <__libc_csu_init+0x40>
> 401226: 48 83 c4 08 add $0x8,%rsp
> 40122a: 5b pop %rbx
> 40122b: 5d pop %rbp
> 40122c: 41 5c pop %r12
> 40122e: 41 5d pop %r13
> 401230: 41 5e pop %r14
> 401232: 41 5f pop %r15
> 401234: c3 retq
> 401235: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
> 40123c: 00 00 00 00
>
> 0000000000401240 <__libc_csu_fini>:
> 401240: f3 0f 1e fa endbr64
> 401244: c3 retq
196,200c195,199
< 0000000000401228 <_fini>:
< 401228: f3 0f 1e fa endbr64
< 40122c: 48 83 ec 08 sub $0x8,%rsp
< 401230: 48 83 c4 08 add $0x8,%rsp
< 401234: c3 retq
---
> 0000000000401248 <_fini>:
> 401248: f3 0f 1e fa endbr64
> 40124c: 48 83 ec 08 sub $0x8,%rsp
> 401250: 48 83 c4 08 add $0x8,%rsp
> 401254: c3 retq
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