Mercurial > pub > dyncall > dyncall
changeset 464:bd65767c0534
doc: two more disas examples
| author | Tassilo Philipp |
|---|---|
| date | Wed, 02 Feb 2022 11:03:06 +0100 |
| parents | bd8f5da2c74b |
| children | e2899b4ff713 |
| files | doc/disas_examples/x64.sysv.disas |
| diffstat | 1 files changed, 71 insertions(+), 0 deletions(-) [+] |
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--- a/doc/disas_examples/x64.sysv.disas Tue Feb 01 22:35:08 2022 +0100 +++ b/doc/disas_examples/x64.sysv.disas Wed Feb 02 11:03:06 2022 +0100 @@ -443,5 +443,76 @@ 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 + + ; vim: ft=asm