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view doc/disas_examples/x86.plan9call.disas @ 472:e5820b7a3fbc
doc:
- some more plan 9 disas examples
- x86 callconv doc updated:
* mainly info about aggregate passing and returning
* removing section about pascal calling convention, as dyncall doesn't support 16bit abis
- some cleanups
| author | Tassilo Philipp |
|---|---|
| date | Thu, 10 Feb 2022 17:32:05 +0100 |
| parents | 97fff5d9cea1 |
| children | ead041d93e36 |
line wrap: on
line source
; void leaf_call(int a, int b, int c, int d, int e, int f) ; { ; } ; ; int nonleaf_call(int a, int b, int c, int d, int e, int f, int g) ; { ; leaf_call(b,c,d,e,f,g); ; return 'x'; ; } ; ; int main() ; { ; nonleaf_call(0,1,2,3,4,5,6); ; return 0; ; } ; output from plan9-4th_edition-x86 w/ 8c x.c && 8l -a x.8 001020 (1) TEXT leaf_call+0(SB),$0 001020 c3 (3) RET , 001021 (5) TEXT nonleaf_call+0(SB),$28 001021 83ec1c (5) SUBL $28,SP ; prolog (note, there is no register save area at all) 001024 8b442424 (7) MOVL b+36(FP),AX ; | 001028 890424 (7) MOVL AX,(SP) ; | 00102b 8b442428 (7) MOVL c+40(FP),AX ; | 00102f 89442404 (7) MOVL AX,4(SP) ; | 001033 8b44242c (7) MOVL d+44(FP),AX ; | 001037 89442408 (7) MOVL AX,8(SP) ; | fetch in args from prev frame's param area ... 00103b 8b442430 (7) MOVL e+48(FP),AX ; | ... and "push" onto stack 00103f 8944240c (7) MOVL AX,12(SP) ; | 001043 8b442434 (7) MOVL f+52(FP),AX ; | 001047 89442410 (7) MOVL AX,16(SP) ; | 00104b 8b442438 (7) MOVL g+56(FP),AX ; | 00104f 89442414 (7) MOVL AX,20(SP) ; | 001053 e8c8ffffff (7) CALL ,1020+leaf_call ; push return address and call 001058 b878000000 (8) MOVL $120,AX ; return value: 'x' -> eax 00105d 83c41c (8) ADDL $28,SP ; | 001060 c3 (8) RET , ; | epilog 001061 (11) TEXT main+0(SB),$32 001061 83ec20 (11) SUBL $32,SP ; prolog (note, there is no register save area at all) 001064 c7042400000000 (13) MOVL $0,(SP) ; arg 0 -> "push" onto stack 00106b b801000000 (13) MOVL $1,AX ; arg 1 -> eax, then ... 001070 89442404 (13) MOVL AX,4(SP) ; ... "pushed" onto stack 001074 b802000000 (13) MOVL $2,AX ; arg 2 -> eax, then ... 001079 89442408 (13) MOVL AX,8(SP) ; ... "pushed" onto stack 00107d b803000000 (13) MOVL $3,AX ; . 001082 8944240c (13) MOVL AX,12(SP) ; . 001086 b804000000 (13) MOVL $4,AX ; . 00108b 89442410 (13) MOVL AX,16(SP) ; . 00108f b805000000 (13) MOVL $5,AX ; . 001094 89442414 (13) MOVL AX,20(SP) ; . 001098 b806000000 (13) MOVL $6,AX ; arg 6 -> eax, then ... 00109d 89442418 (13) MOVL AX,24(SP) ; ... "pushed" onto stack 0010a1 e87bffffff (13) CALL ,1021+nonleaf_call ; push return address and call 0010a6 31c0 (14) MOVL $0,AX ; return value 0010a8 83c420 (14) ADDL $32,SP ; | 0010ab c3 (14) RET , ; | epilog ; ---------- structs by value ----------> ; ; struct A { int i, j; long long l; }; ; ; void leaf_call(int b, int c, int d, int e, struct A f, int g, int h) ; { ; } ; ; void nonleaf_call(int a, int b, int c, int d, int e, struct A f, int g, int h) ; { ; /* use some local data */ ; char l[100] = 'L'; ; leaf_call(b, c, d, e, f, g, h); ; } ; ; int main() ; { ; nonleaf_call(0, 1, 2, 3, 4, (struct A){5, 6, 7ll}, 8, 9); ; return 0; ; } ; output from plan9-4th_edition-x86 w/ 8c x.c && 8l -a x.8 001020 (3) TEXT leaf_call+0(SB),$0 001020 c3 (5) RET , 001021 (7) TEXT nonleaf_call+0(SB),$148 001021 81ec94000000 (7) SUBL $148,SP ; prolog (note, there is no register save area at all) 001027 8d842494000000 (10) LEAL l+148(SP),AX ; | 00102e 89442430 (10) MOVL AX,l+48(SP) ; | loop's write ptr (stored at beginning of char[100] space) 001032 83442430fc (10) ADDL $-4,l+48(SP) ; | decr loop ptr in memory 001037 8b442430 (10) MOVL l+48(SP),AX ; | ptr -> eax 00103b c70000000000 (10) MOVL $0,(AX) ; | zero-init char[100] space write a 0 001041 837c243000 (10) CMPL l+48(SP),$0 ; | cmp if done 001046 75ea (10) JNE ,1032 ; | loop 001048 c64424304c (10) MOVB $76,l+48(SP) ; 'L' -> local area (beginning of char[100] space) 00104d 8b84249c000000 (11) MOVL b+156(FP),AX ; | 001054 890424 (11) MOVL AX,(SP) ; | 001057 8b8424a0000000 (11) MOVL c+160(FP),AX ; | 00105e 89442404 (11) MOVL AX,4(SP) ; | fetch in args (ints before struct) from prev frame's param area ... 001062 8b8424a4000000 (11) MOVL d+164(FP),AX ; | ... and "push" onto stack 001069 89442408 (11) MOVL AX,8(SP) ; | 00106d 8b8424a8000000 (11) MOVL e+168(FP),AX ; | 001074 8944240c (11) MOVL AX,12(SP) ; / 001078 8d7c2410 (11) LEAL 16(SP),DI ; \ dst ptr 00107c 8db424ac000000 (11) LEAL f+172(FP),SI ; | src ptr 001083 b904000000 (11) MOVL $4,CX ; | rep counter (4, for dwords = 16b = sizeof(struct A)) 001088 fc (11) CLD , ; | copy struct to next call's stack 001089 f3 (11) REP , ; | 00108a a5 (11) MOVSL , ; / 00108b 8b8424bc000000 (11) MOVL g+188(FP),AX ; \ 001092 89442420 (11) MOVL AX,32(SP) ; | fetch remaining in args (ints after struct) from prev frame's param area ... 001096 8b8424c0000000 (11) MOVL h+192(FP),AX ; | ... and "push" onto stack 00109d 89442424 (11) MOVL AX,36(SP) ; | 0010a1 e87affffff (11) CALL ,1020+leaf_call ; push return address and call 0010a6 81c494000000 (11) ADDL $148,SP ; | 0010ac c3 (11) RET , ; | epilog 0010ad (14) TEXT main+0(SB),$52 0010ad 83ec34 (14) SUBL $52,SP ; prolog (note, there is no register save area at all) 0010b0 c7042400000000 (16) MOVL $0,(SP) ; arg 0 -> "push" onto stack 0010b7 b801000000 (16) MOVL $1,AX ; arg 1 -> eax, then ... 0010bc 89442404 (16) MOVL AX,4(SP) ; ... "pushed" onto stack 0010c0 b802000000 (16) MOVL $2,AX ; arg 2 -> eax, then ... 0010c5 89442408 (16) MOVL AX,8(SP) ; ... "pushed" onto stack 0010c9 b803000000 (16) MOVL $3,AX ; . 0010ce 8944240c (16) MOVL AX,12(SP) ; . 0010d2 b804000000 (16) MOVL $4,AX ; . 0010d7 89442410 (16) MOVL AX,16(SP) ; . 0010db 8d442414 (16) LEAL 20(SP),AX ; get ptr to next (unused) stack bytes -> eax ... 0010df 89442430 (16) MOVL AX,.safe+48(SP) ; ... and write it to very top of stack (seems aligned and not adjacent to last arg) | looks like callconv keeps a ptr to 0010e3 8b442430 (16) MOVL .safe+48(SP),AX ; regetting of same ptr into eax (pointless as same as in eax) | each struct params in local area 0010e7 c70005000000 (16) MOVL $5,(AX) ; | 0010ed 8b442430 (16) MOVL .safe+48(SP),AX ; | 0010f1 c7400406000000 (16) MOVL $6,4(AX) ; | copy struct linearly to stack, adjacent to other args 0010f8 8b442430 (16) MOVL .safe+48(SP),AX ; | 0010fc c7400807000000 (16) MOVL $7,8(AX) ; | 001103 c7400c00000000 (16) MOVL $0,12(AX) ; | msbytes of long long 00110a b808000000 (16) MOVL $8,AX ; arg 6 -> eax, then ... 00110f 89442424 (16) MOVL AX,36(SP) ; ... "pushed" onto stack 001113 b809000000 (16) MOVL $9,AX ; arg 7 -> eax, then ... 001118 89442428 (16) MOVL AX,40(SP) ; ... "pushed" onto stack 00111c e800ffffff (16) CALL ,1021+nonleaf_call ; push return address and call 001121 31c0 (17) MOVL $0,AX ; return value 001123 83c434 (17) ADDL $52,SP ; | 001126 c3 (17) RET , ; | epilog ; ---------- structs by value, complex example (multiple structs) ----------> ; ; struct A { int i, j; float f; }; ; struct B { double d; long long l; }; ; ; void leaf_call(int b, struct A c, struct B d, int e, int f, struct A g, struct B h, int i, int j) ; { ; } ; ; void nonleaf_call(int a, int b, struct A c, struct B d, int e, int f, struct A g, struct B h, int i, int j) ; { ; /* use some local data */ ; char l[100] = 'L'; ; leaf_call(b, c, d, e, f, g, h, i, j); ; } ; ; int main() ; { ; nonleaf_call(0, 1, (struct A){2, 3, 4.f}, (struct B){5., 6ll}, 7, 8, (struct A){9, 10, 11.f}, (struct B){12., 13ll}, 14, 15); ; return 0; ; } ; output from plan9-4th_edition-x86 w/ 8c x.c && 8l -a x.8 001020 (4) TEXT leaf_call+0(SB),$0 001020 c3 (6) RET , 001021 (8) TEXT nonleaf_call+0(SB),$184 001021 81ecb8000000 (8) SUBL $184,SP 001027 8d8424b8000000 (11) LEAL l+184(SP),AX 00102e 89442454 (11) MOVL AX,l+84(SP) 001032 83442454fc (11) ADDL $-4,l+84(SP) 001037 8b442454 (11) MOVL l+84(SP),AX 00103b c70000000000 (11) MOVL $0,(AX) 001041 837c245400 (11) CMPL l+84(SP),$0 001046 75ea (11) JNE ,1032 001048 c64424544c (11) MOVB $76,l+84(SP) 00104d 8b8424c0000000 (12) MOVL b+192(FP),AX 001054 890424 (12) MOVL AX,(SP) 001057 8d7c2404 (12) LEAL 4(SP),DI 00105b 8db424c4000000 (12) LEAL c+196(FP),SI 001062 b903000000 (12) MOVL $3,CX 001067 fc (12) CLD , 001068 f3 (12) REP , 001069 a5 (12) MOVSL , 00106a 8d7c2410 (12) LEAL 16(SP),DI 00106e 8db424d0000000 (12) LEAL d+208(FP),SI 001075 b904000000 (12) MOVL $4,CX 00107a fc (12) CLD , 00107b f3 (12) REP , 00107c a5 (12) MOVSL , 00107d 8b8424e0000000 (12) MOVL e+224(FP),AX 001084 89442420 (12) MOVL AX,32(SP) 001088 8b8424e4000000 (12) MOVL f+228(FP),AX 00108f 89442424 (12) MOVL AX,36(SP) 001093 8d7c2428 (12) LEAL 40(SP),DI 001097 8db424e8000000 (12) LEAL g+232(FP),SI 00109e b903000000 (12) MOVL $3,CX 0010a3 fc (12) CLD , 0010a4 f3 (12) REP , 0010a5 a5 (12) MOVSL , 0010a6 8d7c2434 (12) LEAL 52(SP),DI 0010aa 8db424f4000000 (12) LEAL h+244(FP),SI 0010b1 b904000000 (12) MOVL $4,CX 0010b6 fc (12) CLD , 0010b7 f3 (12) REP , 0010b8 a5 (12) MOVSL , 0010b9 8b842404010000 (12) MOVL i+260(FP),AX 0010c0 89442444 (12) MOVL AX,68(SP) 0010c4 8b842408010000 (12) MOVL j+264(FP),AX 0010cb 89442448 (12) MOVL AX,72(SP) 0010cf e84cffffff (12) CALL ,1020+leaf_call 0010d4 81c4b8000000 (12) ADDL $184,SP 0010da c3 (12) RET , 0010db (15) TEXT main+0(SB),$100 0010db 83ec64 (15) SUBL $100,SP 0010de c7042400000000 (17) MOVL $0,(SP) 0010e5 b801000000 (17) MOVL $1,AX 0010ea 89442404 (17) MOVL AX,4(SP) 0010ee 8d442408 (17) LEAL 8(SP),AX 0010f2 89442460 (17) MOVL AX,.safe+96(SP) 0010f6 8b442460 (17) MOVL .safe+96(SP),AX 0010fa c70002000000 (17) MOVL $2,(AX) 001100 8b442460 (17) MOVL .safe+96(SP),AX 001104 c7400403000000 (17) MOVL $3,4(AX) 00110b dd0500200000 (17) FMOVD $0.40100000+0(SB),F0 001111 8b442460 (17) MOVL .safe+96(SP),AX 001115 d95808 (17) FMOVFP F0,8(AX) 001118 8d442414 (17) LEAL 20(SP),AX 00111c 8944245c (17) MOVL AX,.safe+92(SP) 001120 dd0508200000 (17) FMOVD $0.40140000+0(SB),F0 001126 8b44245c (17) MOVL .safe+92(SP),AX 00112a dd18 (17) FMOVDP F0,(AX) 00112c 8b44245c (17) MOVL .safe+92(SP),AX 001130 c7400806000000 (17) MOVL $6,8(AX) 001137 c7400c00000000 (17) MOVL $0,12(AX) 00113e b807000000 (17) MOVL $7,AX 001143 89442424 (17) MOVL AX,36(SP) 001147 b808000000 (17) MOVL $8,AX 00114c 89442428 (17) MOVL AX,40(SP) 001150 8d44242c (17) LEAL 44(SP),AX 001154 89442458 (17) MOVL AX,.safe+88(SP) 001158 8b442458 (17) MOVL .safe+88(SP),AX 00115c c70009000000 (17) MOVL $9,(AX) 001162 8b442458 (17) MOVL .safe+88(SP),AX 001166 c740040a000000 (17) MOVL $10,4(AX) 00116d dd0510200000 (17) FMOVD $0.40260000+0(SB),F0 001173 8b442458 (17) MOVL .safe+88(SP),AX 001177 d95808 (17) FMOVFP F0,8(AX) 00117a 8d442438 (17) LEAL 56(SP),AX 00117e 89442454 (17) MOVL AX,.safe+84(SP) 001182 dd0518200000 (17) FMOVD $0.40280000+0(SB),F0 001188 8b442454 (17) MOVL .safe+84(SP),AX 00118c dd18 (17) FMOVDP F0,(AX) 00118e 8b442454 (17) MOVL .safe+84(SP),AX 001192 c740080d000000 (17) MOVL $13,8(AX) 001199 c7400c00000000 (17) MOVL $0,12(AX) 0011a0 b80e000000 (17) MOVL $14,AX 0011a5 89442448 (17) MOVL AX,72(SP) 0011a9 b80f000000 (17) MOVL $15,AX 0011ae 8944244c (17) MOVL AX,76(SP) 0011b2 e86afeffff (17) CALL ,1021+nonleaf_call 0011b7 31c0 (18) MOVL $0,AX 0011b9 83c464 (18) ADDL $100,SP 0011bc c3 (18) RET , 002000 0000000000001040 (17) DATA $0.40100000+0(SB)/8,$(40100000,00000000) 002008 0000000000001440 (17) DATA $0.40140000+0(SB)/8,$(40140000,00000000) 002010 0000000000002640 (17) DATA $0.40260000+0(SB)/8,$(40260000,00000000) 002018 0000000000002840 (17) DATA $0.40280000+0(SB)/8,$(40280000,00000000) ; ---------- returning qwords ----------> ; ; long long f() ; { ; return 7171LL; ; } ; ; int main() ; { ; return (int)f(); ; } ; output from plan9-4th_edition-x86 w/ 8c x.c && 8l -a x.8 001020 (2) TEXT f1+0(SB),$0 001020 8b442404 (4) MOVL .ret+4(FP),AX ; ptr to retval space -> eax 001024 c700031c0000 (4) MOVL $7171,(AX) ; | 00102a c7400400000000 (4) MOVL $0,4(AX) ; | return value 001031 c3 (4) RET , 001032 (7) TEXT main+0(SB),$16 001032 83ec10 (7) SUBL $16,SP ; prolog 001035 8d4c2408 (9) LEAL .safe+8(SP),CX ; | ptr to space for return value ... 001039 890c24 (9) MOVL CX,(SP) ; | ... pushed as implicit first arg 00103c e8dfffffff (9) CALL ,1020+f1 ; push return address and call 001041 8b442408 (9) MOVL .safe+8(SP),AX ; return value 001045 8b54240c (9) MOVL .safe+12(SP),DX ; @@@ unsure, b/c we have a cast 001049 83c410 (9) ADDL $16,SP ; | 00104c c3 (9) RET , ; | epilog ; ---------- returning structs by value ----------> ; ; struct Small { char x; }; ; struct Big { long long i; long j; }; ; ; struct Small f0() ; { ; struct Small s = { 132 }; ; return s; ; } ; ; struct Big f1() ; { ; struct Big b = { 7171LL, 232 }; ; return b; ; } ; ; int main() ; { ; struct Small s = f0(); ; struct Big b = f1(); ; return b.j + s.x; ; } ; output from plan9-4th_edition-x86 w/ 8c x.c && 8l -a x.8 001020 (5) TEXT f0+0 (SB),$16 001020 83ec08 (5) SUBL $8,SP ; prolog 001023 c644240484 (7) MOVB $-124,s+4(SP) ; struct data in local area (s.x) 001028 8b7c240c (8) MOVL .ret+12(FP),DI ; \ 00102c 8d742404 (8) LEAL s+4(SP),SI ; | 001030 b901000000 (8) MOVL $1,CX ; | copy struct in local area to return 001035 fc (8) CLD , ; | value (pointed to by implicit first arg) 001036 f3 (8) REP , ; | 001037 a5 (8) MOVSL , ; / 001038 83c408 (8) ADDL $8,SP ; \ 00103b c3 (8) RET , ; | epilog 00103c (11) TEXT f1+0(SB),$16 00103c 83ec10 (11) SUBL $16,SP ; prolog 00103f c7442404031c0000 (13) MOVL $7171,b+4(SP) ; | | 001047 c744240800000000 (13) MOVL $0,b+8(SP) ; | struct data in local area | b.i 00104f c744240ce8000000 (13) MOVL $232,b+12(SP) ; / b.j 001057 8b7c2414 (14) MOVL .ret+20(FP),DI ; \ 00105b 8d742404 (14) LEAL b+4(SP),SI ; | 00105f b903000000 (14) MOVL $3,CX ; | copy struct in local area to return 001064 fc (14) CLD , ; | value (pointed to by implicit first arg) 001065 f3 (14) REP , ; | 001066 a5 (14) MOVSL , ; / 001067 83c410 (14) ADDL $16,SP ; \ 00106a c3 (14) RET , ; | epilog 00106b (17) TEXT main+0(SB),$28 00106b 83ec1c (17) SUBL $28,SP ; prolog 00106e 8d442418 (19) LEAL s+24(SP),AX ; | ptr to space for return value ... 001072 890424 (19) MOVL AX,(SP) ; | ... pushed as implicit first arg 001075 e8a6ffffff (19) CALL ,1020+f0 ; push return address and call 00107a 8d44240c (20) LEAL b+12(SP),AX ; | ptr to space for return value ... 00107e 890424 (20) MOVL AX,(SP) ; | ... pushed as implicit first arg 001081 e8b6ffffff (20) CALL ,103c+f1 ; push return address and call 001086 0fbe442418 (21) MOVBLSX s+24(SP),AX ; | 00108b 03442414 (21) ADDL b+20(SP),AX ; / return value 00108f 83c41c (21) ADDL $28,SP ; \ 001092 c3 (21) RET , ; | epilog ; vim: ft=asm