Am 14.01.2022 um 03:15 schrieb Ben Grasset via fpc-devel:
On Thu, Jan 13, 2022 at 9:48 AM Nikolay Nikolov via fpc-devel
<fpc-devel@lists.freepascal.org> wrote:
What do other win64 compilers do? Do they generate x87 FPU code
for 64-bit Windows?
Yes. Given the following:
#include <stdio.h>
long double do_three(long double x, long double y, long double z) {
return (((x * x) / y) + z);
}
int main () {
printf("%d\n", sizeof(long double));
printf("%.19Lf\n", do_three(9.4567575785454772685L,
2.1211991522332311497L, 16.1216453784376343456L));
}
GCC 11.2 produces this assembly with "gcc -O3 -march=native -S
test.c" on 64-bit Windows 10:
do_three:
.seh_endprologue
fldt (%rdx)
fldt (%r8)
fldt (%r9)
fxch %st(2)
movq %rcx, %rax
fmul %st(0), %st
fdivp %st, %st(1)
faddp %st, %st(1)
fstpt (%rcx)
ret
.seh_endproc
and Clang 13.0 produces this with the same command line arguments passed:
do_three: # @do_three
# %bb.0:
movq %rcx, %rax
fldt (%rdx)
fldt (%r8)
fldt (%r9)
fxch %st(2)
fmul %st, %st(0)
fdivp %st, %st(1)
faddp %st, %st(1)
fstpt (%rcx)
retq
Running the program prints this with both compilers:
16
58.2818846964779790909
So the answer to Mattias's question about C compilers from before is
"they just directly support it on Windows".
For MSVC it's different:
=== code begin ===
; Function compile flags: /Ogtpy
; File C:\Users\Sven\source\repos\floattest\main.cpp
; COMDAT ?do_three@@YAOOOO@Z
_TEXT SEGMENT
x$ = 8
y$ = 16
z$ = 24
?do_three@@YAOOOO@Z PROC ; do_three, COMDAT
; 4 : return (((x * x) / y) + z);
00000 f2 0f 59 c0 mulsd xmm0, xmm0
00004 f2 0f 5e c1 divsd xmm0, xmm1
00008 f2 0f 58 c2 addsd xmm0, xmm2
; 5 : }
0000c c3 ret 0
?do_three@@YAOOOO@Z ENDP ; do_three
_TEXT ENDS
=== code end ===
=== output begin ===
8
58.2818846964779808673
=== output end ===
(though to be fair it does the same on 32-bit as well)
Regards,
Sven
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