[Issue 15538] wrong code with switch
https://issues.dlang.org/show_bug.cgi?id=15538 --- Comment #8 from Johannes Loher --- I tracked this down a bit. It worked fine till 2.063.2 (including). From 2.064 onward it sarts to segfault. Finally, from 2.068 onward, the assert error starts hppening. --
[Issue 15538] wrong code with switch
https://issues.dlang.org/show_bug.cgi?id=15538 Ketmar Dark changed: What|Removed |Added CC||ket...@ketmar.no-ip.org --
[Issue 15538] wrong code with switch
https://issues.dlang.org/show_bug.cgi?id=15538
--- Comment #7 from aneas ---
Further reduced:
struct S
{
int a = 0;
int b = 1;
}
int f1(S s)
{
switch (s.a)
{
case 0: return 10;
case 1: return 20;
case 2: return 30;
case 3: return 40;
default: return 99;
}
}
void main()
{
S s;
assert(f1(s) == 10); /* fails */
}
The generates assembly for f1 is this:
004271a8 <_D3app2f1FS3app1SZi>:
4271a8:55 push %rbp
4271a9:48 8b ec mov%rsp,%rbp
4271ac:48 83 ec 10 sub$0x10,%rsp
4271b0:48 89 7d f8 mov%rdi,-0x8(%rbp)
4271b4:48 83 ff 03 cmp$0x3,%rdi
4271b8:77 2dja 4271e7 <_D3app2f1FS3app1SZi+0x3f>
4271ba:48 8d 05 a7 3f 02 00 lea0x23fa7(%rip),%rax# 44b168
<_D3app1S6__initZ+0x8>
4271c1:48 63 0c b8 movslq (%rax,%rdi,4),%rcx
4271c5:48 8d 04 01 lea(%rcx,%rax,1),%rax
4271c9:ff e0jmpq *%rax
4271cb:b8 0a 00 00 00 mov$0xa,%eax
4271d0:c9 leaveq
4271d1:c3 retq
4271d2:b8 14 00 00 00 mov$0x14,%eax
4271d7:c9 leaveq
4271d8:c3 retq
4271d9:b8 1e 00 00 00 mov$0x1e,%eax
4271de:c9 leaveq
4271df:c3 retq
4271e0:b8 28 00 00 00 mov$0x28,%eax
4271e5:c9 leaveq
4271e6:c3 retq
4271e7:b8 63 00 00 00 mov$0x63,%eax
4271ec:c9 leaveq
4271ed:c3 retq
...
Dmd packs the whole struct into a single register (%rdi). Since the switch
statement contains consecutive cases, Dmd rightfully tries to skip as many of
them as possible by doing a single comparison (cmp $0x3,%rdi). However, this
comparison is performed on the whole register, which also contains the second
field of the Struct.
--
[Issue 15538] wrong code with switch
https://issues.dlang.org/show_bug.cgi?id=15538 ag0ae...@gmail.com changed: What|Removed |Added CC||alexander.brec...@gmail.com --- Comment #6 from ag0ae...@gmail.com --- *** Issue 17347 has been marked as a duplicate of this issue. *** --
[Issue 15538] wrong code with switch
https://issues.dlang.org/show_bug.cgi?id=15538 --- Comment #5 from Johannes Loher --- In the reduced example, the bug also appears when running in gdb. --
[Issue 15538] wrong code with switch
https://issues.dlang.org/show_bug.cgi?id=15538
ag0ae...@gmail.com changed:
What|Removed |Added
CC||ag0ae...@gmail.com
Summary|final switch statement |wrong code with switch
|raises an exception even|
|though all cases are|
|covered under certain |
|conditions |
--- Comment #4 from ag0ae...@gmail.com ---
Reduced a bit more:
struct S
{
int a = 0;
int b = 1;
}
int f1(int a)
{
switch (a)
{
case 0: return 10;
case 1: return 20;
case 2: return 30;
case 3: return 40;
default: return 99;
}
}
int f2(S s)
{
return f1(s.a);
}
void main()
{
S s;
assert(f1(s.a) == 10); /* passes */
assert(f2(s) == 10); /* fails */
}
(In reply to Sobirari Muhomori from comment #3)
> Does optimization flag -O affect the behavior?
No. -inline has an effect, presumably because f2 is inlined.
--
