Summary:
In theory, care must be taken to ensure that pairs of R_MIPS_(GOT|HI|LO)16
make the same decision on both relocs in the reloc pair but in practice
this isn't as hard as it sounds and only limits the complexity of the
predicate used. We handle all three with the same code to ensure their
decisions always agree with each other.
Reviewers: sdardis
Subscribers: rafael, dsanders, sdardis, llvm-commits
Differential Revision: http://reviews.llvm.org/D19016
llvm-svn: 268900
Summary:
There seems to have been a misunderstanding as to the meaning of 'offset' in
the rules laid down by our ABI. The previous code believed that 'offset' meant
the offset within the section that the relocation is applied to. However, it
should have meant the offset from the symbol used in the relocation expression.
This patch adds two fields to ELFRelocationEntry and uses them to correct the
order of relocations for MIPS. These fields contain:
* The original symbol before shouldRelocateWithSymbol() is considered. This
ensures that R_MIPS_GOT16 is able to correctly distinguish between local and
external symbols, allowing us to tell whether %got() requires a matching
%lo() or not (local symbols require one, external symbols don't). It also
prevents confusing cases where the fuzzy matching rules cause things like
%hi(foo)/%lo(foo+3) and %hi(bar)/%lo(bar+1) to swap their %lo()'s.
* The original offset before shouldRelocateWithSymbol() is considered. The
existing Addend field is always zero when the object uses in place addends
(because it's already moved it to the encoding) but MIPS needs to use the
original offset to ensure that the linker correctly calculates the carry-in
bit for %hi() and %got().
IAS ensures that unmatchable %hi()/%got() relocations are placed at the end of
the table to ensure that the linker rejects the table (we're unable to report
such errors directly). The alternatives to this risk accidental matching
against inappropriate relocations which may silently compute incorrect values
due to an incorrect carry bit between the %lo() and %hi()/%got().
Reviewers: sdardis
Subscribers: dsanders, sdardis, rafael, llvm-commits
Differential Revision: http://reviews.llvm.org/D19718
llvm-svn: 268733
Some targets (ie. Mips) have additional rules for ordering the relocation
table entries. Allow them to override generic sortRelocs(), which sorts
entries by Offset.
Then override this function for Mips, to emit HI16 and GOT16 relocations
against the local symbol in pair with the corresponding LO16 relocation.
Patch by Vladimir Stefanovic.
Differential Revision: http://reviews.llvm.org/D7414
llvm-svn: 234883
