8462cff40d
To make this change, we have to use `lookup` instead of `operator[]` on a map. They both return the same thing: a default constructed value. The difference is that `lookup` default constructs a value and then returns it, whereas `operator[]` default constructs a value, inserts it into the map, and then returns a reference to that. Given that we are using a by-value return, the only way this is different is if a later use of the map depends on a value being at that key. The map is a private variable of the class, so the only possible users are are other member functions. The only other use of the map that cares about the contents of the map is in `lookupInBases`, and it accesses the map with `operator[]`. This means that attempting to access the same element in this function will default construct the value before doing anything with it, which means it would do the exact thing it needs to do in the case where we are looking up a non-existent key, therefore no behavior has changed. In terms of performance, this would either be a win or neutral. The benefit is that in some cases, we can avoid a memory allocation just read the contents of a 32-bit `0`. If a call to `isAmbiguous` is always followed up with a call to `lookupInBases`, then we allocate the memory just a little bit later for no difference in performance.
The LLVM Compiler Infrastructure
Welcome to the LLVM project!
This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.
The LLVM project has multiple components. The core of the project is itself called "LLVM". This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.
C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.
Other components include: the libc++ C++ standard library, the LLD linker, and more.
Getting the Source Code and Building LLVM
Consult the Getting Started with LLVM page for information on building and running LLVM.
For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.
Getting in touch
Join the LLVM Discourse forums, Discord chat, LLVM Office Hours or Regular sync-ups.
The LLVM project has adopted a code of conduct for participants to all modes of communication within the project.