[gcc r12-7376] RISC-V: Document the degree of position independence that medany affords

[gcc r12-7376] RISC-V: Document the degree of position independence that medany affords

[Palmer Dabbelt]

https://gcc.gnu.org/g:8645370af18979123d9e94e3ed215d23dd740721

commit r12-7376-g8645370af18979123d9e94e3ed215d23dd740721
Author: Palmer Dabbelt <palmer@rivosinc.com>
Date:   Thu Jan 13 18:10:19 2022 -0800

    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>

Diff:
---
 gcc/doc/invoke.texi | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index fb3dec4ab0c..ec291c06542 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