LLVM 9.0
lists.llvm.org
LLVM 9.0
1–10 of 111 posts
Re: LLVM 9.0
#2> Support for asm goto, enabling for example the mainline Linux kernel
for x86_64 to build with Clang
This is an awesome step!
Re: LLVM 9.0
#3> "Support for asm goto, enabling for example the mainline Linux kernel for x86_64 to build with Clang"
This is big. Support for asm goto was merged into the mainline earlier this year, but now it's released [1]. Aside from the obvious implications of this - being able to build the kernel with LLVM - working with eBPF/XDP just got way easier [2].
[1] https://github.com/llvm/llvm-project/commit/784929d0454c4df6...
Re: LLVM 9.0
#4>Support for asm goto, enabling for example the mainline Linux kernel for x86_64 to build with Clang
This is great for Linux, no longer being dependent on a single compiler for one of the most popular ISAs can only be a good thing for the overall health of the project. To be clear, I have nothing against gcc.
Re: LLVM 9.0
#5> The optimizer will now convert calls to memcmp into a calls to bcmp in some circumstances.
What is the improvement from that change? I thought they were essentially the same.
Re: LLVM 9.0
#6> The optimizer will now convert calls to memcmp into a calls to bcmp in some circumstances. What is the improvement from that change? I thought they were essentially the same.
bcmp just tells you "equal" or "not equal", while memcmp tells you "lesser", "equal", or "greater".
I don't really know, but I suppose it might be possible to make bcmp faster since you have less strict requirements on the return value.
Re: LLVM 9.0
#7> "Support for asm goto, enabling for example the mainline Linux kernel for x86_64 to build with Clang" This is big. Support for asm goto was merged into the mainline earlier this year, but now it's released [1]. Aside from the obvious implications of this - being able to build the kernel with LLVM - working with eBPF/XDP just got way easier [2]. [1] https://github.com/llvm/llvm-project/commit/784929d0454c4df6... [2]…
Does this mean the Linux x86_64 kernel could only be built with gcc before this LLVM release?
Are there any downfalls of switching from gcc -> LLVM for kernel compilation? Why might somebody want to stick with gcc, why might somebody want to switch to LLVM?
Re: LLVM 9.0
#8Repo of the Linux kernel built with clang:
Re: LLVM 9.0
#9> The optimizer will now convert calls to memcmp into a calls to bcmp in some circumstances. What is the improvement from that change? I thought they were essentially the same.
memcmp returns the lexicographic ordering of the parameters () while bcmp only returns equality (anything nonzero is difference so memcmp is a suitable bcmp), so the LLVM folks believe worst case scenario bcmp will alias to memcmp, and possibly it'll have better performances since it has to do less: https://reviews.llvm.org/D56593
Re: LLVM 9.0
#10> "Support for asm goto, enabling for example the mainline Linux kernel for x86_64 to build with Clang" This is big. Support for asm goto was merged into the mainline earlier this year, but now it's released [1]. Aside from the obvious implications of this - being able to build the kernel with LLVM - working with eBPF/XDP just got way easier [2]. [1] https://github.com/llvm/llvm-project/commit/784929d0454c4df6... [2]…
Does this mean the Linux x86_64 kernel could only be built with gcc before this LLVM release? Are there any downfalls of switching from gcc -> LLVM for kernel compilation? Why might somebody want to stick with gcc, why might somebody want to switch to LLVM?
Mainstream yes. Android has moved to clang for quite a while now, the Linux kernel is the only GPL piece left.