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comparison doc/disas_examples/x86.cdecl.disas @ 469:984e6652b975

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some x86 disas examples, for completion but also while researching struct by val passing on non-x64
author Tassilo Philipp
date Mon, 07 Feb 2022 13:15:49 +0100
parents c0390dc85a07
children 4e84d6faed54
comparison
equal deleted inserted replaced
468:79b95db3d68f 469:984e6652b975
1 ; #include <stdlib.h> 1 ; #include <stdlib.h>
2 ; 2 ;
3 ; void leaf_call(int b, int c, int d, int e, int f, int g, int h) 3 ; void leaf_call(int b, int c, int d, int e, int f, int g, int h)
4 ; { 4 ; {
5 ; } 5 ; }
6 ; 6 ;
7 ; void nonleaf_call(int a, int b, int c, int d, int e, int f, int g, int h) 7 ; void nonleaf_call(int a, int b, int c, int d, int e, int f, int g, int h)
8 ; { 8 ; {
9 ; /* use some local data */ 9 ; /* use some local data */
10 ; *(char*)alloca(220) = 'L'; 10 ; *(char*)alloca(220) = 'L';
11 ; leaf_call(b, c, d, e, f, g, h); 11 ; leaf_call(b, c, d, e, f, g, h);
12 ; } 12 ; }
13 ; 13 ;
14 ; int main() 14 ; int main()
15 ; { 15 ; {
16 ; nonleaf_call(0, 1, 2, 3, 4, 5, 6, 7); 16 ; nonleaf_call(0, 1, 2, 3, 4, 5, 6, 7);
17 ; return 0; 17 ; return 0;
18 ; } 18 ; }
482 b1: c9 leave 482 b1: c9 leave
483 b2: c3 ret 483 b2: c3 ret
484 484
485 485
486 486
487 ; @@@ windows missing 487 ; output from godbolt compiler explorer w/ msvc 19.0
488
489 _leaf_call PROC
490 push ebp
491 mov ebp, esp
492 pop ebp
493 ret 0
494 _leaf_call ENDP
495
496 _b$ = 12
497 _c$ = 16
498 _d$ = 20
499 _e$ = 24
500 _f$ = 28
501 _g$ = 32
502 _h$ = 36
503 _nonleaf_call PROC
504 push ebp
505 mov ebp, esp
506 push 220
507 call _alloca
508 add esp, 4
509 mov BYTE PTR [eax], 76
510 mov eax, DWORD PTR _h$[ebp]
511 push eax
512 mov ecx, DWORD PTR _g$[ebp]
513 push ecx
514 mov edx, DWORD PTR _f$[ebp]
515 push edx
516 mov eax, DWORD PTR _e$[ebp]
517 push eax
518 mov ecx, DWORD PTR _d$[ebp]
519 push ecx
520 mov edx, DWORD PTR _c$[ebp]
521 push edx
522 mov eax, DWORD PTR _b$[ebp]
523 push eax
524 call _leaf_call
525 add esp, 28
526 pop ebp
527 ret 0
528 _nonleaf_call ENDP
529
530 _main PROC
531 push ebp
532 mov ebp, esp
533 push 7
534 push 6
535 push 5
536 push 4
537 push 3
538 push 2
539 push 1
540 push 0
541 call _nonleaf_call
542 add esp, 32
543 xor eax, eax
544 pop ebp
545 ret 0
546 _main ENDP
547
548
549
550 ; ---------- structs by value, struct in first call on reg arg boundary ---------->
551 ;
552 ; struct A { int x; short y; char z; long long t; };
553 ;
554 ; struct A leaf_call(struct A a, short b, long long c, char d, int e, int f, int g, long long h)
555 ; {
556 ; a.x += 1;
557 ; return a;
558 ; }
559 ;
560 ; int main()
561 ; {
562 ; struct A a ={9, 99, 23, 12LL};
563 ; leaf_call(a, 1, 2, 3, 4, 5, 6, 7LL);
564 ; return 0;
565 ; }
566
567
568
569 ; output from godbolt compiler explorer w/ msvc 19.0
570
571 $T1 = 8
572 _a$ = 12
573 _leaf_call PROC
574 push ebp ; | prolog
575 mov ebp, esp ; /
576 mov eax, DWORD PTR _a$[ebp] ; \
577 add eax, 1 ; | get struct's x (from stack args), add 1 and write back
578 mov DWORD PTR _a$[ebp], eax ; /
579 mov ecx, DWORD PTR $T1[ebp] ; get ptr to retval struct passed as hidden arg (+8 to skip retval and saved ebp)
580 mov edx, DWORD PTR _a$[ebp] ; |
581 mov DWORD PTR [ecx], edx ; |
582 mov eax, DWORD PTR _a$[ebp+4] ; |
583 mov DWORD PTR [ecx+4], eax ; | copy modified (b/c of x+=1) struct arg to space of retval
584 mov edx, DWORD PTR _a$[ebp+8] ; |
585 mov DWORD PTR [ecx+8], edx ; |
586 mov eax, DWORD PTR _a$[ebp+12] ; |
587 mov DWORD PTR [ecx+12], eax ; |
588 mov eax, DWORD PTR $T1[ebp] ; return value (= ptr to struct that was passed-in as hidden arg)
589 pop ebp ; |
590 ret 0 ; | epilog
591 _leaf_call ENDP
592
593 $T1 = -32
594 _a$ = -16
595 _main PROC
596 push ebp ; |
597 mov ebp, esp ; | prolog
598 sub esp, 32 ; / 32 = 16b local area for struct + 16b space used for retval struct
599 mov DWORD PTR _a$[ebp], 9 ; \ int x
600 mov eax, 99 ; | |
601 mov WORD PTR _a$[ebp+4], ax ; | struct values (local area) | short y
602 mov BYTE PTR _a$[ebp+6], 23 ; | char z
603 mov DWORD PTR _a$[ebp+8], 12 ; | |
604 mov DWORD PTR _a$[ebp+12], 0 ; / | long long t
605 push 0 ; \
606 push 7 ; | arg 7
607 push 6 ; arg 6
608 push 5 ; arg 5
609 push 4 ; arg 4
610 push 3 ; arg 3
611 push 0 ; |
612 push 2 ; arg 2
613 push 1 ; arg 1
614 sub esp, 16 ; |
615 mov ecx, esp ; |
616 mov edx, DWORD PTR _a$[ebp] ; |
617 mov DWORD PTR [ecx], edx ; |
618 mov eax, DWORD PTR _a$[ebp+4] ; |
619 mov DWORD PTR [ecx+4], eax ; | arg 0 (struct), "pushed" onto stack (fetched from local area)
620 mov edx, DWORD PTR _a$[ebp+8] ; |
621 mov DWORD PTR [ecx+8], edx ; |
622 mov eax, DWORD PTR _a$[ebp+12] ; |
623 mov DWORD PTR [ecx+12], eax ; /
624 lea ecx, DWORD PTR $T1[ebp] ; \ ptr to space used for struct retval (pushed as hidden first arg)
625 push ecx |
626 call _leaf_call ; push return address and call
627 add esp, 56 ; |
628 xor eax, eax ; : return value
629 mov esp, ebp ; |
630 pop ebp ; | epilog
631 ret 0 ; |
632 _main ENDP
633
634
488 635
489 ; vim: ft=asm 636 ; vim: ft=asm
490 637