[Issue 11483] New: dmd inserts a gc allocation where none is required

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11483

           Summary: dmd inserts a gc allocation where none is required
           Product: D
           Version: D2
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: ellery-newcomer at utulsa.edu


--- Comment #0 from Ellery Newcomer <ellery-newcomer at utulsa.edu> 2013-11-09 06:24:22 PST ---
the code:

a.d:
class C
{
    void _InsertAllBut(int v) {
        int* node = null;
        enum mutable = __traits(compiles, {node.value ;});
    }

}

test.d:
import a;

void main () {
    C c = new C();
    c._InsertAllBut(1);
} 

the compilation:

dmd test.d a.d

with dmd 2.063, appears on linux 32 and 64 bit

the disassembly:

...
00000000004178b0 <void a.C._InsertAllBut(int)>:
  4178b0:    55                       push   rbp
  4178b1:    48 8b ec                 mov    rbp,rsp
  4178b4:    48 83 ec 38              sub    rsp,0x38
  4178b8:    53                       push   rbx
  4178b9:    48 89 7d f0              mov    QWORD PTR [rbp-0x10],rdi
  4178bd:    48 bf 10 00 00 00 00     movabs rdi,0x10
  4178c4:    00 00 00 
  4178c7:    e8 e8 21 00 00           call   419ab4 <_d_allocmemory>
  4178cc:    48 89 45 e0              mov    QWORD PTR [rbp-0x20],rax
  4178d0:    48 8b 4d f0              mov    rcx,QWORD PTR [rbp-0x10]
  4178d4:    48 89 08                 mov    QWORD PTR [rax],rcx
  4178d7:    48 85 c9                 test   rcx,rcx
  4178da:    75 35                    jne    417911 <void
a.C._InsertAllBut(int)+0x61>
  4178dc:    41 b8 03 00 00 00        mov    r8d,0x3
  4178e2:    48 8b 0d 8f 8d 01 00     mov    rcx,QWORD PTR [rip+0x18d8f]       
# 430678 <_TMP1+0x8>
  4178e9:    48 8b 05 80 8d 01 00     mov    rax,QWORD PTR [rip+0x18d80]       
# 430670 <_TMP1>
  4178f0:    48 89 c2                 mov    rdx,rax
  4178f3:    48 89 55 d8              mov    QWORD PTR [rbp-0x28],rdx
  4178f7:    48 8b 15 9a 8d 01 00     mov    rdx,QWORD PTR [rip+0x18d9a]       
# 430698 <_TMP2+0x8>
  4178fe:    48 8b 3d 8b 8d 01 00     mov    rdi,QWORD PTR [rip+0x18d8b]       
# 430690 <_TMP2>
  417905:    48 89 d6                 mov    rsi,rdx
  417908:    48 8b 55 d8              mov    rdx,QWORD PTR [rbp-0x28]
  41790c:    e8 5b 19 00 00           call   41926c <_d_assert_msg>
  417911:    48 89 cf                 mov    rdi,rcx
  417914:    e8 6b 21 00 00           call   419a84 <void
invariant._d_invariant(Object)>
  417919:    48 8b 5d e0              mov    rbx,QWORD PTR [rbp-0x20]
  41791d:    48 c7 43 08 00 00 00     mov    QWORD PTR [rbx+0x8],0x0
  417924:    00 
  417925:    5b                       pop    rbx
  417926:    c9                       leave  
  417927:    c3                       ret     
...

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