[Issue 15951] New: Inefficiencies in struct initialization
via Digitalmars-d-bugs
digitalmars-d-bugs at puremagic.com
Sat Apr 23 06:12:18 PDT 2016
https://issues.dlang.org/show_bug.cgi?id=15951
Issue ID: 15951
Summary: Inefficiencies in struct initialization
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P1
Component: dmd
Assignee: nobody at puremagic.com
Reporter: andrei at erdani.com
I list this as an enhancement but it's a blocker for RCStr, which has a
relatively large inline buffer (64 bytes). If that's compulsively initialized,
it makes RCStr nigh unusable as a competitive string.
The simplest case is an entirely uninitialized struct (with the equivalent C++
code):
https://godbolt.org/g/uItGGc
https://godbolt.org/g/6E1mkr
The initialization sequence of the D code is large and slow. What we really
want is to write a 0 in the last byte:
https://godbolt.org/g/twDGbP
https://godbolt.org/g/SRO5ql
Again the D version does a lot of unnecessary work. Where we want to get is
this:
https://godbolt.org/g/B0Xvq3
https://godbolt.org/g/OE6N8C
Here the D version should generate the same code as the C++ version.
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