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| author | Palmer Dabbelt <palmer@rivosinc.com> | 2022-01-13 18:10:19 -0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2022-02-24 11:29:43 -0800 |
| commit | 8645370af18979123d9e94e3ed215d23dd740721 (patch) | |
| tree | cef8546b2f5bbe7cba88f1c5ffc8ee52e51dc69b /gcc/doc | |
| parent | 157cc4e0117756503c7c63df97cf31de7570b088 (diff) | |
| download | gcc-8645370af18979123d9e94e3ed215d23dd740721.zip gcc-8645370af18979123d9e94e3ed215d23dd740721.tar.gz gcc-8645370af18979123d9e94e3ed215d23dd740721.tar.bz2 | |
RISC-V: Document the degree of position independence that medany affords
The code generated by -mcmodel=medany is defined to be
position-independent, but is not guaranteed to function correctly when
linked into position-independent executables or libraries. See the
recent discussion at the psABI specification [1] for more details.
It would be better to reject these invalid sequences when linking, but
as pointed out in a recent LD bug [2] there may be some compatibility
issues related to the PCREL_HI20 relocations used to initialize GP.
Given the complexity here it's unlikely we'll be able to reject these
sequences any time soon, so instead just document that these may not
work.
[1]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/issues/245
[2]: https://sourceware.org/bugzilla/show_bug.cgi?id=28789
gcc/ChangeLog:
* doc/invoke.texi (RISC-V -mcmodel=medany): Document the degree
of position independence that -mcmodel=medany affords.
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'gcc/doc')
| -rw-r--r-- | gcc/doc/invoke.texi | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index fb3dec4..ec291c0 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -27772,6 +27772,10 @@ Generate code for the medium-any code model. The program and its statically defined symbols must be within any single 2 GiB address range. Programs can be statically or dynamically linked. +The code generated by the medium-any code model is position-independent, but is +not guaranteed to function correctly when linked into position-independent +executables or libraries. + @item -mexplicit-relocs @itemx -mno-exlicit-relocs Use or do not use assembler relocation operators when dealing with symbolic |