Do you mean that I should call the testcase '109_calling.c' and add a
comment in this file that this is for x86_64 sse calling?
This is why I called the file '109_sse_calling.c'.
The file name indicates that this is only solving a bug for x86_64.
Herman
On 2019-10-29 08:04, Christian Jullien wrote:
Than you for your recent patch on mod.
I just have a little remark about ' 109_sse_calling' file name.
This new test is executed also on Windows and arm32/64 (which is fine).
However, those backend don't use sse.
IMHO, this test should not have sse in its name but a comment could explain
that the test revealed a bug when see is used as with Linux.
Another solution is to add this new test in 22_floating_point + comment about
sse
-----Original Message-----
From: Tinycc-devel [mailto:tinycc-devel-bounces+eligis=orange...@nongnu.org] On
Behalf Of Michael Matz
Sent: Monday, October 28, 2019 10:32
To: Herman ten Brugge via Tinycc-devel
Cc: Herman ten Brugge
Subject: *** SPAM *** Re: [Tinycc-devel] SSE calling convention bug
Hi,
On Sun, 27 Oct 2019, Herman ten Brugge via Tinycc-devel wrote:
Look like the code in x86_64-gen.c is wrong. It should read:
if (sse_reg) { /* avoid redundant movaps %xmm0, %xmm0
*/
/* movaps %xmm1, %xmmN */
o(0x280f);
o(0xc1 + ((sse_reg+1) << 3));
/* movaps %xmm0, %xmmN */
o(0x280f);
o(0xc0 + (sse_reg << 3));
}
Yes.
Ciao,
Michael.
The problem occurs when sse_reg == 1. Because then xmm1 is overwritten
before it is copied.
Herman
On 2019-10-27 07:32, Christian Jullien wrote:
Trying your sample with mod on Windows -m64/-m32 I get:
c: >tcc -m32 foo.c && foo
5.000000
c:>tcc -m64 foo.c && foo
5.000000
It only return 3.0000 on Linux x64 (I've not tested your code on Linux x86).
C.
-----Original Message-----
From: Tinycc-devel
[mailto:tinycc-devel-bounces+eligis=orange...@nongnu.org]
On Behalf Of Shachaf Ben-Kiki
Sent: Saturday, October 26, 2019 12:59
To: tinycc-devel@nongnu.org
Subject: [Tinycc-devel] SSE calling convention bug
Hello,
I ran into a bug in the SSE function call code in x86_64-gen.c. It's
in the following lines, in gfunc_call:
if (sse_reg) { /* avoid redundant movaps %xmm0, %xmm0 */
/* movaps %xmm0, %xmmN */
o(0x280f);
o(0xc0 + (sse_reg << 3));
/* movaps %xmm1, %xmmN */
o(0x280f);
o(0xc1 + ((sse_reg+1) << 3));
}
When sse_reg is %xmm1, this generates
0f 28 c8 movaps %xmm0,%xmm1
0f 28 d1 movaps %xmm1,%xmm2
Such that the first mov overwrites xmm1 before the second mov uses it.
Since the registers are used in reverse order and only one or two at
a time, I think swapping the order of the movs should be sufficient
to fix it.
Here's a test case:
#include <stdio.h>
struct Point {
float x;
float y;
};
struct Rect {
struct Point top_left;
struct Point size;
};
float foo(struct Point p, struct Rect r) {
return r.size.x;
}
int main(int argc, char **argv) {
struct Point p = {1, 2};
struct Rect r = {{3, 4}, {5, 6}};
printf("%f\n", foo(p, r));
return 0;
}
This program should print 5, but it prints 3 in tcc.
Is this the right place to post this? I can post it elsewhere, or
send a patch (it took a while to track this down but I think the fix
should be easy).
Thanks,
Shachaf
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