3bbc82371e
CALL and JMP on riscv64 are currently implemented as an AUIPC+JALR pair. This means that every call requires two instructions and makes use of the REG_TMP register, even when the symbol would be directly reachable via a single JAL instruction. Add support for call trampolines - CALL and JMP are now implemented as a single JAL instruction, with the linker generating trampolines in the case where the symbol is not reachable (more than +/-1MiB from the JAL instruction), is an unknown symbol or does not yet have an address assigned. Each trampoline contains an AUIPC+JALR pair, which the relocation is applied to. Due to the limited reachability of the JAL instruction, combined with the way that the Go linker currently assigns symbol addresses, there are cases where a call is to a symbol that has no address currently assigned. In this situation we have to assume that a trampoline will be required, however we can patch this up during relocation, potentially calling directly instead. This means that we will end up with trampolines that are unused. In the case of the Go binary, there are around 3,500 trampolines of which approximately 2,300 are unused (around 9200 bytes of machine instructions). Overall, this removes over 72,000 AUIPC instructions from the Go binary. Change-Id: I2d9ecfb85dfc285c7729a3cd0b3a77b6f6c98be0 Reviewed-on: https://go-review.googlesource.com/c/go/+/345051 Trust: Joel Sing <joel@sing.id.au> Run-TryBot: Joel Sing <joel@sing.id.au> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com> |
||
|---|---|---|
| .github | ||
| api | ||
| doc | ||
| lib/time | ||
| misc | ||
| src | ||
| test | ||
| .gitattributes | ||
| .gitignore | ||
| AUTHORS | ||
| CONTRIBUTING.md | ||
| CONTRIBUTORS | ||
| LICENSE | ||
| PATENTS | ||
| README.md | ||
| SECURITY.md | ||
| codereview.cfg | ||
README.md
The Go Programming Language
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
Gopher image by Renee French, licensed under Creative Commons 3.0 Attributions license.
Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.
Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.
Download and Install
Binary Distributions
Official binary distributions are available at https://golang.org/dl/.
After downloading a binary release, visit https://golang.org/doc/install for installation instructions.
Install From Source
If a binary distribution is not available for your combination of operating system and architecture, visit https://golang.org/doc/install/source for source installation instructions.
Contributing
Go is the work of thousands of contributors. We appreciate your help!
To contribute, please read the contribution guidelines at https://golang.org/doc/contribute.
Note that the Go project uses the issue tracker for bug reports and proposals only. See https://golang.org/wiki/Questions for a list of places to ask questions about the Go language.