aboutsummaryrefslogtreecommitdiff
path: root/llvm/lib/Support/VirtualFileSystem.cpp
diff options
context:
space:
mode:
authorEric Fiselier <eric@efcs.ca>2019-09-13 16:09:33 +0000
committerEric Fiselier <eric@efcs.ca>2019-09-13 16:09:33 +0000
commit2a573784f3679a7abab921018eb1c585dce8e669 (patch)
treec68c186474a5b4906b4601c57ab45ce8c06ecd3b /llvm/lib/Support/VirtualFileSystem.cpp
parent69ba3defafa7afc2ddcc0dc0d541334e0220cbb5 (diff)
downloadllvm-2a573784f3679a7abab921018eb1c585dce8e669.zip
llvm-2a573784f3679a7abab921018eb1c585dce8e669.tar.gz
llvm-2a573784f3679a7abab921018eb1c585dce8e669.tar.bz2
Recommit r370502: Make `vector` unconditionally move elements when
exceptions are disabled. The patch was reverted due to some confusion about non-movable types. ie types that explicitly delete their move constructors. However, such types do not meet the requirement for `MoveConstructible`, which is required by `std::vector`: Summary: `std::vector<T>` is free choose between using copy or move operations when it needs to resize. The standard only candidates that the correct exception safety guarantees are provided. When exceptions are disabled these guarantees are trivially satisfied. Meaning vector is free to optimize it's implementation by moving instead of copying. This patch makes `std::vector` unconditionally move elements when exceptions are disabled. This optimization is conforming according to the current standard wording. There are concerns that moving in `-fno-noexceptions`mode will be a surprise to users. For example, a user may be surprised to find their code is slower with exceptions enabled than it is disabled. I'm sympathetic to this surprised, but I don't think it should block this optimization. Reviewers: mclow.lists, ldionne, rsmith Reviewed By: ldionne Subscribers: zoecarver, christof, dexonsmith, libcxx-commits Tags: #libc Differential Revision: https://reviews.llvm.org/D62228 llvm-svn: 371867
Diffstat (limited to 'llvm/lib/Support/VirtualFileSystem.cpp')
0 files changed, 0 insertions, 0 deletions