Linking and linker relaxation fixes #200
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The .sdata section is used for small initialized data by LLVM in order to optimize access to it on some architectures like RISC-V.
The global pointer should be set to cover a range of +-2048 inside frequently accessed data in order to accommodate linker relaxations and improve performance.
DNedic
changed the title
DNedic
changed the title
DNedic
changed the title
DNedic
changed the title
|
The toolchain does not appear to generate gp relative loads still, does zig utilize this feature? |
|
It does appear that relaxation is not enabled in zig: ziglang/zig#3451, I believe this should still be merged now as |
|
@DNedic thank you! |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This PR fixes the following issues:
.sdata*sections being generated. These sections are created by compilers in order to optimize access for small data on some architectures. Right now this breaks theespressif/espexample the.sdataoutput section is being automatically placed at the wrong place, creating an incorrect and enormous binary.__global_pointer$used in the RISC-V architecture CPUs to initialize the GP register. This register is then used in order to improve access times to frequently used data, as long as it is +-2048 bytes away by fitting the offset in the immideate part of the instruction.espressif-riscvReferences:
https://www.sifive.com/blog/all-aboard-part-3-linker-relaxation-in-riscv-toolchain
https://five-embeddev.com/quickref/global_pointer.html
https://d3s.mff.cuni.cz/files/teaching/nswi200/202324/doc/riscv-abi.pdf