buildflags.md: Document downstream build flags

Related: #2005080
This commit is contained in:
Florian Weimer 2021-11-16 17:57:16 +01:00
parent 4358269192
commit 4e35bb887b
1 changed files with 9 additions and 8 deletions

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@ -438,14 +438,15 @@ tuning in the `gcc` package. These settings are:
point math to avoid excess precision issues. `-mstackrealign`
avoids relying on the stack alignment guaranteed by the current
version of the i386 ABI.
* **ppc64le**: `-mcpu=power8 -mtune=power8` selects a minimum supported
CPU level of POWER8 (the first CPU with ppc64le support) and tunes
for POWER8.
* **s390x**: `-march=zEC12 -mtune=z13` specifies a minimum supported CPU
level of zEC12, while optimizing for a subsequent CPU generation
(z13).
* **x86_64**: `-mtune=generic` selects tuning which is expected to
beneficial for a broad range of current CPUs.
* **ppc64le**: `-mcpu=power9 -mtune=power9` selects a minimum supported
CPU level of POWER9.
* **s390x**: `-march=z14 -mtune=z15` specifies a minimum supported CPU
level of z14, while optimizing for a subsequent CPU generation
(z15).
* **x86_64**: `-march=x86-64-v2 -mtune=generic` builds for the
[x86-64-v2 micro-architecture level](https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/low-level-sys-info.tex)
and selects tuning which is expected to beneficial for a broad range
of current CPUs.
* **aarch64** does not have any architecture-specific tuning.
# Individual linker flags