bcl5980 added a comment.
Another thing we need consider here is this case:
#pragma pack(push, 1)
struct b64 {
char a[64];
};
#pragma pack(pop)
typedef b64 (fptrtype)(int a);
b64 f(void* p, int a) {
return ((fptrtype*)p)(a);
}
For now we generate exit_thunk with type void f(void* sret(b64) ret, int a)
$iexit_thunk$cdecl$v$i8i8: // @"$iexit_thunk$cdecl$v$i8i8"
.seh_proc $iexit_thunk$cdecl$v$i8i8
// %bb.0:
sub sp, sp, #48
.seh_stackalloc 48
stp x29, x30, [sp, #32] // 16-byte Folded Spill
.seh_save_fplr 32
add x29, sp, #32
.seh_add_fp 32
.seh_endprologue
mov w1, w0
mov x0, x8
adrp x8, __os_arm64x_dispatch_call_no_redirect
ldr x8, [x8, :lo12:__os_arm64x_dispatch_call_no_redirect]
blr x8
.seh_startepilogue
ldp x29, x30, [sp, #32] // 16-byte Folded Reload
.seh_save_fplr 32
add sp, sp, #48
.seh_stackalloc 48
.seh_endepilogue
ret
.seh_endfunclet
.seh_endproc
// -- End function
.globl f
.def f;
.scl 2;
.type 32;
.endef
But it looks Microsoft generate exit thunk with type void* f(int a)
|$iexit_thunk$cdecl$i8$i8| PROC
|$LN2|
pacibsp
stp fp,lr,[sp,#-0x10]!
mov fp,sp
sub sp,sp,#0x20
adrp x8,__os_arm64x_dispatch_call_no_redirect
ldr xip0,[x8,__os_arm64x_dispatch_call_no_redirect]
blr xip0
mov x0,x8
add sp,sp,#0x20
ldp fp,lr,[sp],#0x10
autibsp
ret
ENDP ; |$iexit_thunk$cdecl$i8$i8|
But based on clang x86 on Windows, we also generate the function type with void
f(void* sret(b64) ret, int a).
It looks clang is different from MSVC even in x86 ABI.
Do we need to follow MSVC to generate $iexit_thunk$cdecl$i8$i8 ? Or just follow
clang's ABI and ignore the difference?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D125418/new/
https://reviews.llvm.org/D125418
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