On 7/2/2010 6:10 PM, Jonathan M Davis wrote:
DMD doesn't inline functions that could throw? Isn't that rather restrictive?
I'm assuming that that's functions with an actual throw statement rather than
all functions that aren't nothrow, since that would _really_ be restrictive. But
still, you could have a really small function that threw if a condition failed
but otherwise just returned a value, and I would have thought that that would be
worth inlining. I'm far from an expert once you're dealing with stuff that low-
level, so there could be a very good reason that functions that could throw
aren't inlined, but it does strike me as rather restrictive if you can't inline
such functions.
- Jonathan M Davis
Yeah, I've started looking into this a little more. DMD will not inline
anything with a throw statement, though it will inline functions that
are not nothrow. However, in practice calling enforce() seems to
prevent inlining of any function that uses enforce() because enforce()
also has a lazy parameter, which isn't always visible because it has a
default. For example:
import std.contracts : enforce;
void main(string[] args) {
getNum();
}
__gshared bool dummy = true;
uint getNum() {
enforce(dummy);
return 1;
}
The fact that getNum() isn't inlined seems ridiculous at first, until
you see the disassembly of it. enforce() is inlined because it doesn't
contain a throw statement. std.contracts.bailOut() actually throws the
exception. Here's the horribly complicated disassembly of getNum():
_D5test96getNumFZk PROC NEAR
; COMDEF _D5test96getNumFZk
sub esp, 24 ; 0000 _ 83. EC, 18
xor eax, eax ; 0003 _ 31. C0
mov ecx, offset
FLAT:_D5test96getNumFZk14__dgliteral610MFZAxa; 0005 _ B9, 00000000(segrel)
push ebx ; 000A _ 53
mov dl, byte ptr [_D5test95dummyb] ; 000B _ 8A.
15, 00000000(segrel)
xor dl, 01H ; 0011 _ 80. F2, 01
mov dword ptr [esp+4H], eax ; 0014 _ 89. 44
24, 04
mov dword ptr [esp+8H], ecx ; 0018 _ 89. 4C
24, 08
jz ?_007 ; 001C _ 74, 21
mov edx, ecx ; 001E _ 8B. D1
push dword ptr [?_003] ; 0020 _ FF.
35, 00000014(segrel)
push dword ptr [?_002] ; 0026 _ FF.
35, 00000010(segrel)
push 10 ; 002C _ 6A, 0A
mov eax, dword ptr [esp+10H] ; 002E _ 8B. 44
24, 10
mov ebx, dword ptr [esp+10H] ; 0032 _ 8B. 5C
24, 10
call edx ; 0036 _ FF. D2
push edx ; 0038 _ 52
push eax ; 0039 _ 50
call _D3std9contracts7bailOutFAyaixAaZv ; 003A _ E8,
00000000(rel)
?_007: mov eax, 1 ; 003F _ B8,
00000001
pop ebx ; 0044 _ 5B
add esp, 24 ; 0045 _ 83. C4, 18
ret ; 0048 _ C3
_D5test96getNumFZk ENDP
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