mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-04-08 09:43:20 +00:00
aba6559370
Late optimization passes like branch folding and tail duplication can transform the machine code in a way that makes it expensive to keep the register liveness information up to date. There is a fuzzy line between register allocation and late scheduling where the liveness information degrades. The MRI::tracksLiveness() flag makes the line clear: While true, liveness information is accurate, and can be used for register scavenging. Once the flag is false, liveness information is not accurate, and can only be used as a hint. Late passes generally don't need the liveness information, but they will sometimes use the register scavenger to help update it. The scavenger enforces strict correctness, and we have to spend a lot of code to update register liveness that may never be used. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153511 91177308-0d34-0410-b5e6-96231b3b80d8
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for the Low Level Virtual Machine, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the HTML documentation provided in docs/index.html for further assistance with LLVM. If you're writing a package for LLVM, see docs/Packaging.html for our suggestions.