Re: D ASM. Program fails
On 22.01.2016 21:34, Iakh wrote: This code returns 0 for any input v It seems to return 5 here: http://dpaste.dzfl.pl/85fb8e5c4b6b
Re: D ASM. Program fails
On Friday, 22 January 2016 at 17:27:35 UTC, userABCabc123 wrote:
int pmovmskb(byte16 v)
{
asm
{
naked;
push RBP;
mov RBP, RSP;
sub RSP, 0x10;
movdqa dword ptr[RBP-0x10], XMM0;
movdqa XMM0, dword ptr[RBP-0x10];
pmovmskb EAX, XMM0;
mov RSP, RBP;
pop RBP;
ret;
}
}
Thanks. It works.
Buth shorter version too:
asm
{
naked;
push RBP;
mov RBP, RSP;
//sub RSP, 0x10;
//movdqa dword ptr[RBP-0x10], XMM0;
//movdqa XMM0, dword ptr[RBP-0x10];
pmovmskb EAX, XMM0;
mov RSP, RBP;
pop RBP;
ret;
}
Looks like the SIMD param is passed by SIMD reg
Re: D ASM. Program fails
On Friday, 22 January 2016 at 12:18:53 UTC, anonymous wrote:
int pmovmskb(byte16 v)
{
int r;
asm
{
movdqa XMM0, v;
pmovmskb EAX, XMM0;
mov r, EAX;
}
return r;
}
This code returns 0 for any input v
Removed the `inout` because it doesn't make sense. You may be
looking for `ref`.
yeah
Re: D ASM. Program fails
On Friday, 22 January 2016 at 20:41:23 UTC, anonymous wrote: On 22.01.2016 21:34, Iakh wrote: This code returns 0 for any input v It seems to return 5 here: http://dpaste.dzfl.pl/85fb8e5c4b6b Yeah. Sorry. My bad.
Re: D ASM. Program fails
On Friday, 22 January 2016 at 20:54:46 UTC, Iakh wrote:
On Friday, 22 January 2016 at 17:27:35 UTC, userABCabc123 wrote:
[...]
Thanks. It works.
Buth shorter version too:
asm
{
naked;
push RBP;
mov RBP, RSP;
//sub RSP, 0x10;
//movdqa dword ptr[RBP-0x10], XMM0;
//movdqa XMM0, dword ptr[RBP-0x10];
pmovmskb EAX, XMM0;
mov RSP, RBP;
pop RBP;
ret;
}
Looks like the SIMD param is passed by SIMD reg
Right I must be blind. So you can even remove the prelude and the
prologue:
int pmovmskb2(byte16 v)
{
asm
{
naked;
pmovmskb EAX, XMM0;
ret;
}
}
Re: D ASM. Program fails
On 22.01.2016 06:59, Iakh wrote:
import std.stdio;
import core.simd;
int pmovmskb(inout byte16 v)
{
asm
{
movdqa XMM0, v;
pmovmskb EAX, XMM0;
ret;
}
}
void main()
{
byte16 a = [-1, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
auto i = pmovmskb(a);
}
I don't know much about these things, but it seems to be the `ret;`.
This doesn't segfault:
int pmovmskb(byte16 v)
{
int r;
asm
{
movdqa XMM0, v;
pmovmskb EAX, XMM0;
mov r, EAX;
}
return r;
}
Removed the `inout` because it doesn't make sense. You may be looking
for `ref`.
Re: D ASM. Program fails
On Friday, 22 January 2016 at 14:06:42 UTC, Adam D. Ruppe wrote:
On Friday, 22 January 2016 at 12:18:53 UTC, anonymous wrote:
I don't know much about these things, but it seems to be the
`ret;`.
Right. This is an ordinary D function so the compiler generates
code to set up a stack for local variables. It looks like:
push ebp;
mov ebp, esp;
sub EBP, some_size;
/* sometimes a few other register saves */
/*
your code here
*/
/* sometimes a few other register restores */
leave;
ret;
`leave` btw is the same as `mov esp,ebp; pop ebp;` - it undoes
the result of those first three instructions.
All this setup stuff is about creating a stack frame for the
function's local variables. If you ret without restoring the
frame, all local variables (and return addresses!) from there
on are going to be out of sync and will lead to memory access
violations. That's what happened to you.
If you want to write a whole function in assembly without the
compiler inserting any additional code, start it off with `asm
{ naked; }` inside so dmd knows what you are trying to do. Then
you are in complete control.
Otherwise, remember to clear the frame correctly, or better
yet, just return using the ordinary D statement instead of the
asm instruction.
naked version:
int pmovmskb2(byte16 v)
{
asm
{
naked;
push RBP;
mov RBP, RSP;
sub RSP, 0x20;
movdqa dword ptr[RBP-0x10], XMM0;
mov dword ptr[RBP-0x18], 0;
movdqa XMM0, dword ptr[RBP-0x10];
pmovmskb EAX, XMM0;
mov RSP, RBP;
pop RBP;
ret;
}
}
Note that there is maybe a DMD codegen bug because the asm
generated for the non naked version copy the result to the stack
and then the stack to result but after pmovmskb it's already
setup in EAX.
0044C580h push rbp
0044C581h mov rbp, rsp
0044C584h sub rsp, 20h
0044C588h movdqa dqword ptr [rbp-10h], xmm0
0044C58Dh mov dword ptr [rbp-18h], h
0044C594h movdqa xmm0, dqword ptr [rbp-10h]
0044C599h pmovmskb eax, xmm0 ; already in result
0044C59Dh mov dword ptr [rbp-18h], eax ; what?
0044C5A0h mov eax, dword ptr [rbp-18h] ; what?
0044C5A3h mov rsp, rbp
0044C5A6h pop rbp
0044C5A7h ret
Re: D ASM. Program fails
On Friday, 22 January 2016 at 12:18:53 UTC, anonymous wrote:
I don't know much about these things, but it seems to be the
`ret;`.
Right. This is an ordinary D function so the compiler generates
code to set up a stack for local variables. It looks like:
push ebp;
mov ebp, esp;
sub EBP, some_size;
/* sometimes a few other register saves */
/*
your code here
*/
/* sometimes a few other register restores */
leave;
ret;
`leave` btw is the same as `mov esp,ebp; pop ebp;` - it undoes
the result of those first three instructions.
All this setup stuff is about creating a stack frame for the
function's local variables. If you ret without restoring the
frame, all local variables (and return addresses!) from there on
are going to be out of sync and will lead to memory access
violations. That's what happened to you.
If you want to write a whole function in assembly without the
compiler inserting any additional code, start it off with `asm {
naked; }` inside so dmd knows what you are trying to do. Then you
are in complete control.
Otherwise, remember to clear the frame correctly, or better yet,
just return using the ordinary D statement instead of the asm
instruction.
Re: D ASM. Program fails
On Friday, 22 January 2016 at 17:12:25 UTC, userABCabc123 wrote:
Note that there is maybe a DMD codegen bug because the asm
generated for the non naked version copy the result to the
stack and then the stack to result but after pmovmskb it's
already setup in EAX.
0044C580h push rbp
0044C581h mov rbp, rsp
0044C584h sub rsp, 20h
0044C588h movdqa dqword ptr [rbp-10h], xmm0
0044C58Dh mov dword ptr [rbp-18h], h
0044C594h movdqa xmm0, dqword ptr [rbp-10h]
0044C599h pmovmskb eax, xmm0 ; already in result
0044C59Dh mov dword ptr [rbp-18h], eax ; what?
0044C5A0h mov eax, dword ptr [rbp-18h] ; what?
0044C5A3h mov rsp, rbp
0044C5A6h pop rbp
0044C5A7h ret
Oops, there no DMD codegen bug, the non naked version explicitly
uses a local value for the return so without the local "r" this
gives:
int pmovmskb(byte16 v)
{
asm
{
naked;
push RBP;
mov RBP, RSP;
sub RSP, 0x10;
movdqa dword ptr[RBP-0x10], XMM0;
movdqa XMM0, dword ptr[RBP-0x10];
pmovmskb EAX, XMM0;
mov RSP, RBP;
pop RBP;
ret;
}
}
D ASM. Program fails
This code compiles but program exits with code -11
What's wrong?
import std.stdio;
import core.simd;
int pmovmskb(inout byte16 v)
{
asm
{
movdqa XMM0, v;
pmovmskb EAX, XMM0;
ret;
}
}
void main()
{
byte16 a = [-1, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
auto i = pmovmskb(a);
}
Program exited with code -11
DMD64 D Compiler v2.069
