On Monday, 20 February 2017 at 12:47:43 UTC, berni wrote:
pragma(inline, true) doesn't work out well:
int bar;
void main(string[] args)
{
if (foo()) {}
}
bool foo()
{
pragma(inline, true)
if (bar==1) return false;
if (bar==2) return false;
return true;
}
with
dmd -inline test.d
I get
test.d(8): Error: function test.foo cannot inline function
Because dmd's semantic analysis determined that it doesn't know
how to inline the function and since you insisted that it must be
inlined, you received an error. This is an issue with dmd. ldc2
happily inlines your function:
---
$ ldc2 --version
LDC - the LLVM D compiler (1.1.0):
based on DMD v2.071.2 and LLVM 3.9.1
built with DMD64 D Compiler v2.072.2
Default target: x86_64-pc-linux-gnu
$ ldc2 -c test.d
$ objdump -dr test.o
test.o: file format elf64-x86-64
Disassembly of section .text._Dmain:
0000000000000000 <_Dmain>:
0: 53 push %rbx
1: 48 83 ec 20 sub $0x20,%rsp
5: 48 89 7c 24 10 mov %rdi,0x10(%rsp)
a: 48 89 74 24 18 mov %rsi,0x18(%rsp)
f: 66 48 8d 3d 00 00 00 data16 lea 0x0(%rip),%rdi # 17
<_Dmain+0x17>
16: 00
13: R_X86_64_TLSGD _D4test3bari-0x4
17: 66 66 48 e8 00 00 00 data16 data16 callq 1f <_Dmain+0x1f>
1e: 00
1b: R_X86_64_PLT32 __tls_get_addr-0x4
1f: 8b 18 mov (%rax),%ebx
21: 83 fb 01 cmp $0x1,%ebx
24: 75 0a jne 30 <_Dmain+0x30>
26: 31 c0 xor %eax,%eax
28: 88 c1 mov %al,%cl
2a: 88 4c 24 0f mov %cl,0xf(%rsp)
2e: eb 29 jmp 59 <_Dmain+0x59>
30: 66 48 8d 3d 00 00 00 data16 lea 0x0(%rip),%rdi # 38
<_Dmain+0x38>
37: 00
34: R_X86_64_TLSGD _D4test3bari-0x4
38: 66 66 48 e8 00 00 00 data16 data16 callq 40 <_Dmain+0x40>
3f: 00
3c: R_X86_64_PLT32 __tls_get_addr-0x4
40: 8b 18 mov (%rax),%ebx
42: 83 fb 02 cmp $0x2,%ebx
45: 75 0a jne 51 <_Dmain+0x51>
47: 31 c0 xor %eax,%eax
49: 88 c1 mov %al,%cl
4b: 88 4c 24 0f mov %cl,0xf(%rsp)
4f: eb 08 jmp 59 <_Dmain+0x59>
51: b0 01 mov $0x1,%al
53: 88 44 24 0f mov %al,0xf(%rsp)
57: eb 00 jmp 59 <_Dmain+0x59>
59: 8a 44 24 0f mov 0xf(%rsp),%al
5d: a8 01 test $0x1,%al
5f: 75 02 jne 63 <_Dmain+0x63>
61: eb 02 jmp 65 <_Dmain+0x65>
63: eb 00 jmp 65 <_Dmain+0x65>
65: 31 c0 xor %eax,%eax
67: 48 83 c4 20 add $0x20,%rsp
6b: 5b pop %rbx
6c: c3 retq
---
When I remove -inline, it compiles, but seems not to inline. I
cannot tell from this small example, but with the large
program, there is no speed gain.
I'd suggest inspecting the generated assembly in order to
determine whether your function was inlined or not (see above
using objdump for Linux).
It also compiles with -inline when I remove the "if
(bar==2)...". I guess, it's now really inlining, but the
function is ridiculously short...
I don't know, but I'd guess that the length of a function is not
as important for the consideration of being inlined as its
semantics.
