Mercurial > pub > dyncall > dyncall
view doc/disas_examples/x64.sysv.disas @ 499:fc614cb865c6
- doc and disasexample additions specific to non-trivial C++ aggregates as return values (incl. fixes to doc and additional LSB specific PPC32 section)
| author | Tassilo Philipp |
|---|---|
| date | Mon, 04 Apr 2022 15:50:52 +0200 |
| parents | 75cb8f79d725 |
| children | f1810b5dbb3b |
line wrap: on
line source
; #include <stdlib.h> ; ; void leaf_call(int b, int c, int d, int e, int f, int g, int h) ; { ; } ; ; void nonleaf_call(int a, int b, int c, int d, int e, int f, int g, int h) ; { ; /* use some local data */ ; *(char*)alloca(10) = 'L'; ; leaf_call(b, c, d, e, f, g, h); ; } ; ; int main() ; { ; nonleaf_call(0, 1, 2, 3, 4, 5, 6, 7); ; return 0; ; } ; output from freebsd-12.0-x64 w/ clang 6.0.1 0000000000000000 <leaf_call>: 0: 55 push %rbp 1: 48 89 e5 mov %rsp,%rbp 4: 8b 45 10 mov 0x10(%rbp),%eax 7: 89 7d fc mov %edi,-0x4(%rbp) a: 89 75 f8 mov %esi,-0x8(%rbp) d: 89 55 f4 mov %edx,-0xc(%rbp) 10: 89 4d f0 mov %ecx,-0x10(%rbp) 13: 44 89 45 ec mov %r8d,-0x14(%rbp) 17: 44 89 4d e8 mov %r9d,-0x18(%rbp) 1b: 89 45 e4 mov %eax,-0x1c(%rbp) 1e: 5d pop %rbp 1f: c3 retq 0000000000000020 <nonleaf_call>: 20: 55 push %rbp ; | 21: 48 89 e5 mov %rsp,%rbp ; | prolog 24: 48 83 ec 40 sub $0x40,%rsp ; | open frame *with* static alloca() size included 28: 8b 45 18 mov 0x18(%rbp),%eax ; unsure... get stack param from prev frame into some scratch reg... but why? see below @@@ 2b: 44 8b 55 10 mov 0x10(%rbp),%r10d ; unsure... get stack param from prev frame into some scratch reg... but why? see below @@@ 2f: 89 7d fc mov %edi,-0x4(%rbp) ; in arg 0 -> local area (as temp store) 32: 89 75 f8 mov %esi,-0x8(%rbp) ; in arg 1 -> local area (as temp store) 35: 89 55 f4 mov %edx,-0xc(%rbp) ; in arg 2 -> local area (as temp store) 38: 89 4d f0 mov %ecx,-0x10(%rbp) ; in arg 3 -> local area (as temp store) 3b: 44 89 45 ec mov %r8d,-0x14(%rbp) ; in arg 4 -> local area (as temp store) 3f: 44 89 4d e8 mov %r9d,-0x18(%rbp) ; in arg 5 -> local area (as temp store) 43: c6 45 d0 4c movb $0x4c,-0x30(%rbp) ; 'L' -> local area (of alloca()'d space) 47: 8b 7d f8 mov -0x8(%rbp),%edi ; arg 0 4a: 8b 75 f4 mov -0xc(%rbp),%esi ; arg 1 4d: 8b 55 f0 mov -0x10(%rbp),%edx ; arg 2 50: 8b 4d ec mov -0x14(%rbp),%ecx ; arg 3 53: 44 8b 45 e8 mov -0x18(%rbp),%r8d ; arg 4 57: 44 8b 4d 10 mov 0x10(%rbp),%r9d ; arg 5 (fetched from prev frame's param area - behind return addr on 16b aligned stack) 5b: 44 8b 5d 18 mov 0x18(%rbp),%r11d ; arg 6 (fetched from prev frame's param area), and ... 5f: 44 89 1c 24 mov %r11d,(%rsp) ; ... "pushed" onto stack 63: 44 89 55 cc mov %r10d,-0x34(%rbp) ; unsure... write something to local area @@@? 67: 89 45 c8 mov %eax,-0x38(%rbp) ; unsure... write something to local area @@@? 6a: e8 91 ff ff ff callq 0 <leaf_call> ; push return addr and call 6f: 48 83 c4 40 add $0x40,%rsp ; | 73: 5d pop %rbp ; | epilog 74: c3 retq ; | 75: 66 66 2e 0f 1f 84 00 nopw %cs:0x0(%rax,%rax,1) ; garbage data 7c: 00 00 00 00 ; garbage data 0000000000000080 <main>: 80: 55 push %rbp ; | 81: 48 89 e5 mov %rsp,%rbp ; | prolog 84: 48 83 ec 20 sub $0x20,%rsp ; | 88: 31 ff xor %edi,%edi ; arg 0 8a: be 01 00 00 00 mov $0x1,%esi ; arg 1 8f: ba 02 00 00 00 mov $0x2,%edx ; arg 2 94: b9 03 00 00 00 mov $0x3,%ecx ; arg 3 99: 41 b8 04 00 00 00 mov $0x4,%r8d ; arg 4 9f: 41 b9 05 00 00 00 mov $0x5,%r9d ; arg 5 a5: b8 06 00 00 00 mov $0x6,%eax ; unsure... see below @@@? aa: 41 ba 07 00 00 00 mov $0x7,%r10d ; unsure... see below @@@? b0: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%rbp) ; unsure... write 0 to local area @@@? b7: c7 04 24 06 00 00 00 movl $0x6,(%rsp) ; "push" arg6 onto stack be: c7 44 24 08 07 00 00 00 movl $0x7,0x8(%rsp) ; "push" arg7 onto stack c6: 44 89 55 f8 mov %r10d,-0x8(%rbp) ; unsure... write something to local area @@@? ca: 89 45 f4 mov %eax,-0xc(%rbp) ; unsure... write something to local area @@@? cd: e8 4e ff ff ff callq 20 <nonleaf_call> ; push return addr and call d2: 31 c0 xor %eax,%eax ; return value d4: 48 83 c4 20 add $0x20,%rsp ; | d8: 5d pop %rbp ; | epilog d9: c3 retq ; | ; output from arch_linux-2011.08.19-x64 w/ gcc 4.6.1 (w/ alloca(220) instead of 10) 0000000000000000 <leaf_call>: 0: 55 push %rbp 1: 48 89 e5 mov %rsp,%rbp 4: 89 7d fc mov %edi,-0x4(%rbp) 7: 89 75 f8 mov %esi,-0x8(%rbp) a: 89 55 f4 mov %edx,-0xc(%rbp) d: 89 4d f0 mov %ecx,-0x10(%rbp) 10: 44 89 45 ec mov %r8d,-0x14(%rbp) 14: 44 89 4d e8 mov %r9d,-0x18(%rbp) 18: 5d pop %rbp 19: c3 retq 000000000000001a <nonleaf_call>: 1a: 55 push %rbp 1b: 48 89 e5 mov %rsp,%rbp 1e: 48 83 ec 30 sub $0x30,%rsp 22: 89 7d fc mov %edi,-0x4(%rbp) 25: 89 75 f8 mov %esi,-0x8(%rbp) 28: 89 55 f4 mov %edx,-0xc(%rbp) 2b: 89 4d f0 mov %ecx,-0x10(%rbp) 2e: 44 89 45 ec mov %r8d,-0x14(%rbp) 32: 44 89 4d e8 mov %r9d,-0x18(%rbp) 36: b8 10 00 00 00 mov $0x10,%eax 3b: 48 83 e8 01 sub $0x1,%rax 3f: 48 05 eb 00 00 00 add $0xeb,%rax 45: 48 c7 45 e0 10 00 00 00 movq $0x10,-0x20(%rbp) 4d: ba 00 00 00 00 mov $0x0,%edx 52: 48 f7 75 e0 divq -0x20(%rbp) 56: 48 6b c0 10 imul $0x10,%rax,%rax 5a: 48 29 c4 sub %rax,%rsp 5d: 48 8d 44 24 08 lea 0x8(%rsp),%rax 62: 48 83 c0 0f add $0xf,%rax 66: 48 c1 e8 04 shr $0x4,%rax 6a: 48 c1 e0 04 shl $0x4,%rax 6e: c6 00 4c movb $0x4c,(%rax) 71: 44 8b 45 e8 mov -0x18(%rbp),%r8d 75: 8b 4d ec mov -0x14(%rbp),%ecx 78: 8b 55 f0 mov -0x10(%rbp),%edx 7b: 8b 75 f4 mov -0xc(%rbp),%esi 7e: 8b 45 f8 mov -0x8(%rbp),%eax 81: 8b 7d 18 mov 0x18(%rbp),%edi 84: 89 3c 24 mov %edi,(%rsp) 87: 44 8b 4d 10 mov 0x10(%rbp),%r9d 8b: 89 c7 mov %eax,%edi 8d: e8 00 00 00 00 callq 92 <nonleaf_call+0x78> 92: c9 leaveq 93: c3 retq 0000000000000094 <main>: 94: 55 push %rbp 95: 48 89 e5 mov %rsp,%rbp 98: 48 83 ec 10 sub $0x10,%rsp 9c: c7 44 24 08 07 00 00 00 movl $0x7,0x8(%rsp) a4: c7 04 24 06 00 00 00 movl $0x6,(%rsp) ab: 41 b9 05 00 00 00 mov $0x5,%r9d b1: 41 b8 04 00 00 00 mov $0x4,%r8d b7: b9 03 00 00 00 mov $0x3,%ecx bc: ba 02 00 00 00 mov $0x2,%edx c1: be 01 00 00 00 mov $0x1,%esi c6: bf 00 00 00 00 mov $0x0,%edi cb: e8 00 00 00 00 callq d0 <main+0x3c> d0: b8 00 00 00 00 mov $0x0,%eax d5: c9 leaveq d6: c3 retq ; ---------- structs by value, struct in first call on reg arg boundary ----------> ; ; #include <stdlib.h> ; ; 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*)alloca(220) = '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 freebsd-12.2-x64 w/ clang 10.0.1 0000000000201920 <leaf_call>: 201920: 55 push %rbp 201921: 48 89 e5 mov %rsp,%rbp 201924: 8b 45 18 mov 0x18(%rbp),%eax 201927: 44 8b 55 10 mov 0x10(%rbp),%r10d 20192b: 4c 89 45 f0 mov %r8,-0x10(%rbp) 20192f: 4c 89 4d f8 mov %r9,-0x8(%rbp) 201933: 89 7d ec mov %edi,-0x14(%rbp) 201936: 89 75 e8 mov %esi,-0x18(%rbp) 201939: 89 55 e4 mov %edx,-0x1c(%rbp) 20193c: 89 4d e0 mov %ecx,-0x20(%rbp) 20193f: 5d pop %rbp 201940: c3 retq 201941: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1) 20194b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 0000000000201950 <nonleaf_call>: 201950: 55 push %rbp ; | 201951: 48 89 e5 mov %rsp,%rbp ; | prolog 201954: 53 push %rbx ; | 201955: 48 81 ec 18 01 00 00 sub $0x118,%rsp ; | open frame *with* static alloca() size included 20195c: 8b 45 20 mov 0x20(%rbp),%eax ; unsure... stack param from prev frame into some scratch reg... but why? see below @@@ 20195f: 4c 8d 55 10 lea 0x10(%rbp),%r10 ; ptr to struct on stack -> r10 201963: 89 7d f4 mov %edi,-0xc(%rbp) ; | 201966: 89 75 f0 mov %esi,-0x10(%rbp) ; | 201969: 89 55 ec mov %edx,-0x14(%rbp) ; | 20196c: 89 4d e8 mov %ecx,-0x18(%rbp) ; | in args (regs) -> local area (as temp store, mem order 8,4,3,2,1,0) 20196f: 44 89 45 e4 mov %r8d,-0x1c(%rbp) ; | 201973: 44 89 4d e0 mov %r9d,-0x20(%rbp) ; | 201977: c6 85 00 ff ff ff 4c movb $0x4c,-0x100(%rbp) ; 'L' -> local area (of alloca()'d space) 20197e: 8b 7d f0 mov -0x10(%rbp),%edi ; arg 0 201981: 8b 75 ec mov -0x14(%rbp),%esi ; arg 1 201984: 8b 55 e8 mov -0x18(%rbp),%edx ; arg 2 201987: 8b 4d e4 mov -0x1c(%rbp),%ecx ; arg 3 20198a: 44 8b 45 e0 mov -0x20(%rbp),%r8d ; in arg 6 (local copy) -> r8 pointless, free regs available and using arg reg as temporary, needs freeing below 20198e: 44 8b 4d 20 mov 0x20(%rbp),%r9d ; in arg 7 (stack) -> r9 pointless, free regs available and using arg reg as temporary, needs freeing below 201992: 4d 8b 1a mov (%r10),%r11 ; in arg 5 (A.i, A.j) -> hold in scratch reg 201995: 4d 8b 52 08 mov 0x8(%r10),%r10 ; in arg 5 (A.l) -> hold in scratch reg 201999: 44 89 85 fc fe ff ff mov %r8d,-0x104(%rbp) ; 'free' r8, temp store content 2019a0: 4d 89 d8 mov %r11,%r8 ; arg 4 (A.i, A.j) 2019a3: 44 89 8d f8 fe ff ff mov %r9d,-0x108(%rbp) ; 'free' r9, temp store content 2019aa: 4d 89 d1 mov %r10,%r9 ; arg 4 (A.l) 2019ad: 8b 9d fc fe ff ff mov -0x104(%rbp),%ebx ; \ 2019b3: 89 1c 24 mov %ebx,(%rsp) ; / arg 5 (fetch from temp store, pushed) pointless, could've been pushed, directly 2019b6: 8b 9d f8 fe ff ff mov -0x108(%rbp),%ebx ; \ 2019bc: 89 5c 24 08 mov %ebx,0x8(%rsp) ; / arg 6 (fetch from temp store, pushed) pointless, could've been pushed, directly 2019c0: 89 85 f4 fe ff ff mov %eax,-0x10c(%rbp) ; unsure... write something to local area @@@? 2019c6: e8 55 ff ff ff callq 201920 <leaf_call> ; push return addr and call 2019cb: 48 81 c4 18 01 00 00 add $0x118,%rsp ; | 2019d2: 5b pop %rbx ; | 2019d3: 5d pop %rbp ; | epilog 2019d4: c3 retq ; | 2019d5: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1) ; garbage data 2019df: 90 nop ; garbage data 00000000002019e0 <main>: 2019e0: 55 push %rbp ; | 2019e1: 48 89 e5 mov %rsp,%rbp ; | prolog 2019e4: 48 83 ec 30 sub $0x30,%rsp ; | 2019e8: 31 ff xor %edi,%edi ; arg 0 2019ea: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%rbp) ; unsure... write 0 to local area @@@? 2019f1: c7 45 e8 05 00 00 00 movl $0x5,-0x18(%rbp) ; | field i 2019f8: c7 45 ec 06 00 00 00 movl $0x6,-0x14(%rbp) ; | fill struct A (local area) field j 2019ff: 48 c7 45 f0 07 00 00 00 movq $0x7,-0x10(%rbp) ; | field l 201a07: be 01 00 00 00 mov $0x1,%esi ; arg 1 201a0c: ba 02 00 00 00 mov $0x2,%edx ; arg 2 201a11: b9 03 00 00 00 mov $0x3,%ecx ; arg 3 201a16: 41 b8 04 00 00 00 mov $0x4,%r8d ; arg 4 201a1c: 48 8d 45 e8 lea -0x18(%rbp),%rax ; | 201a20: 4c 8b 08 mov (%rax),%r9 ; | 201a23: 4c 89 0c 24 mov %r9,(%rsp) ; | arg 5 (struct, pushed onto stack, as not enough regs) 201a27: 48 8b 40 08 mov 0x8(%rax),%rax ; | 201a2b: 48 89 44 24 08 mov %rax,0x8(%rsp) ; | 201a30: 41 b9 08 00 00 00 mov $0x8,%r9d ; arg 6 (in reg) 201a36: c7 44 24 10 09 00 00 00 movl $0x9,0x10(%rsp) ; arg 7 (pushed) 201a3e: e8 0d ff ff ff callq 201950 <nonleaf_call> ; push return addr and call 201a43: 31 c0 xor %eax,%eax ; return value 201a45: 48 83 c4 30 add $0x30,%rsp ; | 201a49: 5d pop %rbp ; | epilog 201a4a: c3 retq ; | ; ---------- structs by value, complex example (multiple structs, partly passed via regs) ----------> ; ; #include <stdlib.h> ; ; 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*)alloca(220) = '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 freebsd-12.2-x64 w/ clang 10.0.1 0000000000201940 <leaf_call>: 201940: 55 push %rbp 201941: 48 89 e5 mov %rsp,%rbp 201944: 8b 45 28 mov 0x28(%rbp),%eax 201947: 44 8b 55 20 mov 0x20(%rbp),%r10d 20194b: 48 89 75 e0 mov %rsi,-0x20(%rbp) 20194f: f3 0f 11 45 e8 movss %xmm0,-0x18(%rbp) 201954: 48 8b 75 e0 mov -0x20(%rbp),%rsi 201958: 48 89 75 f0 mov %rsi,-0x10(%rbp) 20195c: 44 8b 5d e8 mov -0x18(%rbp),%r11d 201960: 44 89 5d f8 mov %r11d,-0x8(%rbp) 201964: f2 0f 11 4d d0 movsd %xmm1,-0x30(%rbp) 201969: 48 89 55 d8 mov %rdx,-0x28(%rbp) 20196d: 4c 89 4d b0 mov %r9,-0x50(%rbp) 201971: f3 0f 11 55 b8 movss %xmm2,-0x48(%rbp) 201976: 48 8b 55 b0 mov -0x50(%rbp),%rdx 20197a: 48 89 55 c0 mov %rdx,-0x40(%rbp) 20197e: 44 8b 5d b8 mov -0x48(%rbp),%r11d 201982: 44 89 5d c8 mov %r11d,-0x38(%rbp) 201986: 89 7d ac mov %edi,-0x54(%rbp) 201989: 89 4d a8 mov %ecx,-0x58(%rbp) 20198c: 44 89 45 a4 mov %r8d,-0x5c(%rbp) 201990: 5d pop %rbp 201991: c3 retq 201992: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1) 20199c: 0f 1f 40 00 nopl 0x0(%rax) 00000000002019a0 <nonleaf_call>: 2019a0: 55 push %rbp ; | 2019a1: 48 89 e5 mov %rsp,%rbp ; | 2019a4: 41 57 push %r15 ; | 2019a6: 41 56 push %r14 ; | prolog 2019a8: 41 54 push %r12 ; | 2019aa: 53 push %rbx ; | 2019ab: 48 81 ec 70 01 00 00 sub $0x170,%rsp ; | open frame *with* static alloca() size included 2019b2: 8b 45 38 mov 0x38(%rbp),%eax ; unsure... get last (15) stack param from prev frame into some scratch reg... but why? see below @@@ 2019b5: 44 8b 55 30 mov 0x30(%rbp),%r10d ; unsure... get one to last (14) stack param from prev frame into some scratch reg... but why? see below @@@ 2019b9: 4c 8d 5d 20 lea 0x20(%rbp),%r11 ; ptr to struct B on stack -> rbx 2019bd: 48 8d 5d 10 lea 0x10(%rbp),%rbx ; ptr to struct A on stack -> r11 2019c1: 48 89 55 c0 mov %rdx,-0x40(%rbp) ; | \ i, j 2019c5: f3 0f 11 45 c8 movss %xmm0,-0x38(%rbp) ; | / reassemble first struct A in mem (local area) f 2019ca: 48 8b 55 c0 mov -0x40(%rbp),%rdx ; . \ pointless reload of rdx w/ same val from same addr 2019ce: 48 89 55 d0 mov %rdx,-0x30(%rbp) ; . | 2019d2: 44 8b 75 c8 mov -0x38(%rbp),%r14d ; . | copy of just reassembled A (local area) @@@ unsure why (@@@ I think we need copies of the structs, all the time) 2019d6: 44 89 75 d8 mov %r14d,-0x28(%rbp) ; . / 2019da: f2 0f 11 4d b0 movsd %xmm1,-0x50(%rbp) ; | \ d 2019df: 48 89 4d b8 mov %rcx,-0x48(%rbp) ; | / reassemble first struct B in mem (local area) l 2019e3: 89 7d ac mov %edi,-0x54(%rbp) ; | (0) 2019e6: 89 75 a8 mov %esi,-0x58(%rbp) ; | in args (regs) -> local area (as temp store, mem order 8,7,1,0,B,A,A') (1) 2019e9: 44 89 45 a4 mov %r8d,-0x5c(%rbp) ; | (7) 2019ed: 44 89 4d a0 mov %r9d,-0x60(%rbp) ; | (8) 2019f1: c6 85 a0 fe ff ff 4c movb $0x4c,-0x160(%rbp) ; 'L' -> local area (of alloca()'d space) 2019f8: 8b 7d a8 mov -0x58(%rbp),%edi ; arg 0 2019fb: 8b 4d a4 mov -0x5c(%rbp),%ecx ; arg 3 2019fe: 44 8b 45 a0 mov -0x60(%rbp),%r8d ; arg 4 201a02: 8b 75 30 mov 0x30(%rbp),%esi ; in arg 9 -> hold in scratch reg 201a05: 44 8b 4d 38 mov 0x38(%rbp),%r9d ; in arg 8 -> hold in scratch reg 201a09: 48 8b 55 d0 mov -0x30(%rbp),%rdx ; | again pointless reload of rdx w/ same val from same addr 201a0d: 48 89 55 90 mov %rdx,-0x70(%rbp) ; | 201a11: 44 8b 75 d8 mov -0x28(%rbp),%r14d ; | *another* copy of copy of A (local area) @@@ unsure why 201a15: 44 89 75 98 mov %r14d,-0x68(%rbp) ; | 201a19: 48 8b 55 90 mov -0x70(%rbp),%rdx ; pointless reload of rdx 201a1d: f3 0f 10 45 98 movss -0x68(%rbp),%xmm0 ; arg 1 (A.f) @@@ unsure why from copy 201a22: f2 0f 10 4d b0 movsd -0x50(%rbp),%xmm1 ; arg 2 (B.d) 201a27: 4c 8b 7d b8 mov -0x48(%rbp),%r15 ; in arg arg 3 (B.l) -> hold in scratch reg 201a2b: 4c 8b 23 mov (%rbx),%r12 ; | 201a2e: 4c 89 65 80 mov %r12,-0x80(%rbp) ; | 201a32: 44 8b 73 08 mov 0x8(%rbx),%r14d ; | copy of in arg 6 (struct A on stack) -> local area 201a36: 44 89 75 88 mov %r14d,-0x78(%rbp) ; | 201a3a: 48 8b 5d 80 mov -0x80(%rbp),%rbx ; in arg 6 (A.i, A.j) -> rbx 201a3e: f3 0f 10 55 88 movss -0x78(%rbp),%xmm2 ; arg 5 (A.f) 201a43: 89 b5 9c fe ff ff mov %esi,-0x164(%rbp) ; in arg 9 -> temp (at end of frame, a bit pointless as could be pushed directly) 201a49: 48 89 d6 mov %rdx,%rsi ; arg 1 (A.i, A.j) 201a4c: 4c 89 fa mov %r15,%rdx ; arg 2 (B.l) 201a4f: 44 89 8d 98 fe ff ff mov %r9d,-0x168(%rbp) ; in arg 8 -> temp (at end of frame, a bit pointless as could be pushed directly) 201a56: 49 89 d9 mov %rbx,%r9 ; arg 5 (A.i, A.j) 201a59: 49 8b 1b mov (%r11),%rbx ; \ 201a5c: 48 89 1c 24 mov %rbx,(%rsp) ; / arg 6 (B.d) (pushed) 201a60: 4d 8b 5b 08 mov 0x8(%r11),%r11 ; \ 201a64: 4c 89 5c 24 08 mov %r11,0x8(%rsp) ; / arg 6 (B.l) (pushed) 201a69: 44 8b b5 9c fe ff ff mov -0x164(%rbp),%r14d ; \ 201a70: 44 89 74 24 10 mov %r14d,0x10(%rsp) ; / arg 7 (pushed, aligned) 201a75: 44 8b b5 98 fe ff ff mov -0x168(%rbp),%r14d ; \ 201a7c: 44 89 74 24 18 mov %r14d,0x18(%rsp) ; / arg 8 (pushed, aligned) 201a81: 89 85 94 fe ff ff mov %eax,-0x16c(%rbp) ; unsure... write something to local area @@@? 201a87: 44 89 95 90 fe ff ff mov %r10d,-0x170(%rbp) ; unsure... write something to local area @@@? 201a8e: e8 ad fe ff ff callq 201940 <leaf_call> ; push return addr and call 201a93: 48 81 c4 70 01 00 00 add $0x170,%rsp ; | 201a9a: 5b pop %rbx ; | 201a9b: 41 5c pop %r12 ; | 201a9d: 41 5e pop %r14 ; | epilog 201a9f: 41 5f pop %r15 ; | 201aa1: 5d pop %rbp ; | 201aa2: c3 retq ; | 201aa3: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1) ; garbage data 201aad: 0f 1f 00 nopl (%rax) ; garbage data 0000000000201ab0 <main>: 201ab0: 55 push %rbp ; | 201ab1: 48 89 e5 mov %rsp,%rbp ; | prolog 201ab4: 48 81 ec 80 00 00 00 sub $0x80,%rsp ; | 201abb: 31 ff xor %edi,%edi ; arg 0 201abd: f2 0f 10 05 2b ea ff ff movsd -0x15d5(%rip),%xmm0 ; not arg: prep to fill struct B field d (12.0) 201ac5: f3 0f 10 0d 2f ea ff ff movss -0x15d1(%rip),%xmm1 ; not arg: prep to fill struct A field f (11.f) 201acd: f2 0f 10 15 13 ea ff ff movsd -0x15ed(%rip),%xmm2 ; not arg: prep to fill struct B field d (5.0) 201ad5: f3 0f 10 1d 1b ea ff ff movss -0x15e5(%rip),%xmm3 ; not arg: prep to fill struct A field f (4.f) 201add: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%rbp) ; unsure... write 0 to local area @@@? 201ae4: c7 45 f0 02 00 00 00 movl $0x2,-0x10(%rbp) ; \ field i 201aeb: c7 45 f4 03 00 00 00 movl $0x3,-0xc(%rbp) ; | fill first struct A (local area) field j 201af2: f3 0f 11 5d f8 movss %xmm3,-0x8(%rbp) ; / field f 201af7: f2 0f 11 55 e0 movsd %xmm2,-0x20(%rbp) ; \ field d 201afc: 48 c7 45 e8 06 00 00 00 movq $0x6,-0x18(%rbp) ; / fill first struct B (local area) field l 201b04: c7 45 d0 09 00 00 00 movl $0x9,-0x30(%rbp) ; \ field i 201b0b: c7 45 d4 0a 00 00 00 movl $0xa,-0x2c(%rbp) ; | fill last struct A (local area) field j 201b12: f3 0f 11 4d d8 movss %xmm1,-0x28(%rbp) ; / field f 201b17: f2 0f 11 45 c0 movsd %xmm0,-0x40(%rbp) ; \ field d 201b1c: 48 c7 45 c8 0d 00 00 00 movq $0xd,-0x38(%rbp) ; / fill last struct B (local area) field l 201b24: 48 8b 45 f0 mov -0x10(%rbp),%rax ; \ 201b28: 48 89 45 b0 mov %rax,-0x50(%rbp) ; | unsure ... make copy of first struct A (local area) @@@ 201b2c: 8b 4d f8 mov -0x8(%rbp),%ecx ; | 201b2f: 89 4d b8 mov %ecx,-0x48(%rbp) ; / 201b32: 48 8b 55 b0 mov -0x50(%rbp),%rdx ; arg 2 (A.i, A.j) @@@ unsure why from copy made above 201b36: f3 0f 10 45 b8 movss -0x48(%rbp),%xmm0 ; arg 2 (A.f) @@@ unsure why from copy made above 201b3b: f2 0f 10 4d e0 movsd -0x20(%rbp),%xmm1 ; arg 3 (B.d) 201b40: 48 8b 4d e8 mov -0x18(%rbp),%rcx ; arg 3 (B.l) 201b44: be 01 00 00 00 mov $0x1,%esi ; arg 1 201b49: 41 b8 07 00 00 00 mov $0x7,%r8d ; arg 4 201b4f: 41 b9 08 00 00 00 mov $0x8,%r9d ; arg 5 201b55: 48 8d 45 d0 lea -0x30(%rbp),%rax ; \ \ 201b59: 4c 8b 10 mov (%rax),%r10 ; | | i, j 201b5c: 4c 89 14 24 mov %r10,(%rsp) ; | arg 6 (last struct A, *pushed* by value) / 201b60: 44 8b 58 08 mov 0x8(%rax),%r11d ; | \ f 201b64: 44 89 5c 24 08 mov %r11d,0x8(%rsp) ; / / 201b69: 48 8d 45 c0 lea -0x40(%rbp),%rax ; \ \ 201b6d: 4c 8b 10 mov (%rax),%r10 ; | | d (aligned) 201b70: 4c 89 54 24 10 mov %r10,0x10(%rsp) ; | arg 7 (last struct B, *pushed* by value) / 201b75: 48 8b 40 08 mov 0x8(%rax),%rax ; | \ l 201b79: 48 89 44 24 18 mov %rax,0x18(%rsp) ; / / 201b7e: c7 44 24 20 0e 00 00 00 movl $0xe,0x20(%rsp) ; arg 8 (pushed, aligned) 201b86: c7 44 24 28 0f 00 00 00 movl $0xf,0x28(%rsp) ; arg 9 (pushed, aligned) 201b8e: e8 0d fe ff ff callq 2019a0 <nonleaf_call> ; push return addr and call 201b93: 31 c0 xor %eax,%eax ; return value 201b95: 48 81 c4 80 00 00 00 add $0x80,%rsp ; | 201b9c: 5d pop %rbp ; | epilog 201b9d: c3 retq ; | ; ---------- returning tiny struct by value (passes via regs) ----------> ; ; struct A { unsigned char a; }; ; ; struct A call(unsigned char c) ; { ; return (struct A){c}; ; } ; ; int main() ; { ; struct A a = call(123); ; return 0; ; } ; output from freebsd-12.2-x64 w/ clang 10.0.1 00000000002018f0 <call>: 2018f0: 55 push %rbp ; | 2018f1: 48 89 e5 mov %rsp,%rbp ; | prolog 2018f4: 40 88 7d f7 mov %dil,-0x9(%rbp) ; in arg 0 -> local area, ... | a bit pointless, could've been 2018f8: 8a 45 f7 mov -0x9(%rbp),%al ; ... from local area -> eax, then ... | moved to -0x8(%rbp) directly 2018fb: 88 45 f8 mov %al,-0x8(%rbp) ; ... to struct in local area 2018fe: 8a 45 f8 mov -0x8(%rbp),%al ; return value 201901: 5d pop %rbp ; | epilog 201902: c3 retq ; | 201903: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1) ; garbage data 20190d: 0f 1f 00 nopl (%rax) ; garbage data 0000000000201910 <main>: 201910: 55 push %rbp ; | 201911: 48 89 e5 mov %rsp,%rbp ; | prolog 201914: 48 83 ec 10 sub $0x10,%rsp ; | 201918: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%rbp) ; @@@ unsure, clears dword of local area 20191f: bf 7b 00 00 00 mov $0x7b,%edi ; arg 0 (123) 201924: e8 c7 ff ff ff callq 2018f0 <call> ; push return addr and call 201929: 31 c9 xor %ecx,%ecx ; return value prep (a bit pointless) 20192b: 88 45 f8 mov %al,-0x8(%rbp) ; write struct data to local area (123) 20192e: 89 c8 mov %ecx,%eax ; return value 201930: 48 83 c4 10 add $0x10,%rsp ; | 201934: 5d pop %rbp ; | epilog 201935: c3 retq ; | ; output from freebsd-12.2-x64 w/ gcc 10.3.0 00000000004007a5 <call>: 4007a5: 55 push %rbp ; | 4007a6: 48 89 e5 mov %rsp,%rbp ; | prolog 4007a9: 89 f8 mov %edi,%eax ; in arg 0 ... 4007ab: 88 45 fc mov %al,-0x4(%rbp) ; ... -> struct in local area 4007ae: 0f b6 45 fc movzbl -0x4(%rbp),%eax ; return value (entire struct in eax) 4007b2: 5d pop %rbp ; | epilog 4007b3: c3 retq ; | 00000000004007b4 <main>: 4007b4: 55 push %rbp ; | 4007b5: 48 89 e5 mov %rsp,%rbp ; | prolog 4007b8: 48 83 ec 10 sub $0x10,%rsp ; | 4007bc: bf 7b 00 00 00 mov $0x7b,%edi ; arg 0 (123) 4007c1: e8 df ff ff ff callq 4007a5 <call> ; push return addr and call 4007c6: 88 45 ff mov %al,-0x1(%rbp) ; write struct data to local area (123) 4007c9: b8 00 00 00 00 mov $0x0,%eax ; return value 4007ce: c9 leaveq ; | 4007cf: c3 retq ; | epilog ; ---------- C++ trivial and non-trivial aggrs passed to C funcs ----------> ; ; struct Trivial { int a; }; ; struct NonTrivial { int a; NonTrivial() : a(0) {} NonTrivial(const NonTrivial& rhs) : a(rhs.a) { } }; ; ; extern "C" { ; ; void f1(struct Trivial s) { } ; void f2(struct NonTrivial s) { } ; ; void f() ; { ; struct Trivial t; ; struct NonTrivial n; ; int a=1; ; a += 123; ; f1(t); ; a -= 123; ; f2(n); ; a -= 12; ; } ; } ; output from freebsd-12.2-x64 w/ clang 10.0.1 0000000000000000 <f1>: 0: 55 push %rbp ; | prolog 1: 48 89 e5 mov %rsp,%rbp ; | 4: 89 7d f8 mov %edi,-0x8(%rbp) ; local copy of trivial struct 7: 5d pop %rbp ; | 8: c3 retq ; | epilog 0000000000000010 <f2>: 10: 55 push %rbp ; | prolog 11: 48 89 e5 mov %rsp,%rbp ; / 14: 5d pop %rbp ; \ note: no local copy as non-trivial 15: c3 retq ; | epilog 0000000000000020 <f>: 20: 55 push %rbp ; | 21: 48 89 e5 mov %rsp,%rbp ; | prolog 24: 48 83 ec 20 sub $0x20,%rsp ; / 28: 48 8d 7d f0 lea -0x10(%rbp),%rdi ; \ this ptr (NULL) 2c: e8 00 00 00 00 callq 31 <f+0x11> ; | NonTrivial::NonTrivial() / ctor 31: c7 45 ec 01 00 00 00 movl $0x1,-0x14(%rbp) ; a = 1 38: 8b 45 ec mov -0x14(%rbp),%eax ; | 3b: 83 c0 7b add $0x7b,%eax ; | a += 123 3e: 89 45 ec mov %eax,-0x14(%rbp) ; / 41: 8b 45 f8 mov -0x8(%rbp),%eax ; \ 44: 89 45 e8 mov %eax,-0x18(%rbp) ; / local copy of t (struct Trivial) 47: 8b 7d e8 mov -0x18(%rbp),%edi ; f1 arg 0 (struct Trivial), via reg as small struct 4a: e8 00 00 00 00 callq 4f <f+0x2f> ; call f1(struct Trivial) 4f: 8b 45 ec mov -0x14(%rbp),%eax ; | 52: 83 e8 7b sub $0x7b,%eax ; | a -= 123 55: 89 45 ec mov %eax,-0x14(%rbp) ; / 58: 48 8d 7d e0 lea -0x20(%rbp),%rdi ; \ ptr to dest of copy of n 5c: 48 8d 75 f0 lea -0x10(%rbp),%rsi ; | copy n ptr to n 60: e8 00 00 00 00 callq 65 <f+0x45> ; / NonTrivial::NonTrivial(const NonTrivial&) / copy ctor 65: 48 8d 7d e0 lea -0x20(%rbp),%rdi ; f2 arg 0 (ptr to copy of struct NonTrivial), via ptr as non-trivial 69: e8 00 00 00 00 callq 6e <f+0x4e> ; call f2(struct NonTrivial) 6e: 8b 45 ec mov -0x14(%rbp),%eax ; | 71: 83 e8 0c sub $0xc,%eax ; | a -= 12 74: 89 45 ec mov %eax,-0x14(%rbp) ; / 77: 48 83 c4 20 add $0x20,%rsp ; \ 7b: 5d pop %rbp ; | epilog 7c: c3 retq ; | ; ... snip, removed code of ctor and copy ctor ... ; ---------- C++ trivial and non-trivial aggrs as return values ----------> ; ; struct Trivial { int a; }; ; struct NonTrivial { int a; NonTrivial() : a(0) {} NonTrivial(const NonTrivial& rhs) : a(rhs.a) { } }; ; ; extern "C" { ; struct Trivial f1() { return Trivial(); } ; } ; ; struct NonTrivial f2() { return NonTrivial(); } ; ; extern "C" { ; void f() ; { ; int a=1; ; a += 123; ; struct Trivial t = f1(); ; a -= 123; ; struct NonTrivial n = f2(); ; a -= 12; ; } ; } ; output from freebsd-12.2-x64 w/ clang 10.0.1 00000000002019c0 <f1>: 2019c0: 55 push %rbp 2019c1: 48 89 e5 mov %rsp,%rbp 2019c4: 48 83 ec 10 sub $0x10,%rsp 2019c8: 31 f6 xor %esi,%esi 2019ca: 48 8d 45 f8 lea -0x8(%rbp),%rax 2019ce: 48 89 c7 mov %rax,%rdi 2019d1: ba 04 00 00 00 mov $0x4,%edx 2019d6: e8 75 01 00 00 callq 201b50 <memset@plt> 2019db: 8b 45 f8 mov -0x8(%rbp),%eax 2019de: 48 83 c4 10 add $0x10,%rsp 2019e2: 5d pop %rbp 2019e3: c3 retq 00000000002019f0 <_Z2f2v>: 2019f0: 55 push %rbp 2019f1: 48 89 e5 mov %rsp,%rbp 2019f4: 48 83 ec 10 sub $0x10,%rsp 2019f8: 48 89 f8 mov %rdi,%rax 2019fb: 48 89 f9 mov %rdi,%rcx 2019fe: 48 89 4d f8 mov %rcx,-0x8(%rbp) 201a02: 48 89 45 f0 mov %rax,-0x10(%rbp) 201a06: e8 85 00 00 00 callq 201a90 <_ZN10NonTrivialC2Ev> 201a0b: 48 8b 45 f0 mov -0x10(%rbp),%rax 201a0f: 48 83 c4 10 add $0x10,%rsp 201a13: 5d pop %rbp 201a14: c3 retq 0000000000201a20 <f>: 201a20: 55 push %rbp ; | 201a21: 48 89 e5 mov %rsp,%rbp ; | prolog 201a24: 48 83 ec 10 sub $0x10,%rsp ; | 201a28: c7 45 fc 01 00 00 00 movl $0x1,-0x4(%rbp) ; a = 1 201a2f: 8b 45 fc mov -0x4(%rbp),%eax ; | 201a32: 83 c0 7b add $0x7b,%eax ; | a += 123 201a35: 89 45 fc mov %eax,-0x4(%rbp) ; | 201a38: e8 83 ff ff ff callq 2019c0 <f1> ; call f1() 201a3d: 89 45 f8 mov %eax,-0x8(%rbp) ; retval via reg, as small struct 201a40: 8b 45 fc mov -0x4(%rbp),%eax ; | 201a43: 83 e8 7b sub $0x7b,%eax ; | a -= 123 201a46: 89 45 fc mov %eax,-0x4(%rbp) ; | 201a49: 48 8d 7d f0 lea -0x10(%rbp),%rdi ; ptr to space to hold non-triv retval 201a4d: e8 9e ff ff ff callq 2019f0 <_Z2f2v> ; call f2() 201a52: 8b 45 fc mov -0x4(%rbp),%eax ; | 201a55: 83 e8 0c sub $0xc,%eax ; | a-= 12 201a58: 89 45 fc mov %eax,-0x4(%rbp) ; / 201a5b: 48 83 c4 10 add $0x10,%rsp ; \ 201a5f: 5d pop %rbp ; | epilog 201a60: c3 retq ; | ; vim: ft=asm