Commit Graph

6 Commits

Author SHA1 Message Date
Rui Ueyama 9db06423d1 Remove full stops from error messages for consistency.
llvm-svn: 345294
2018-10-25 18:07:55 +00:00
Peter Smith a8656c62f5 [ELF] Add support for Armv5 and Armv6 compatible Thunks
Older Arm architectures do not support the MOVT and MOVW instructions so we
must use an alternative sequence of instructions to transfer control to the
destination.

Assuming at least Armv5 this patch adds support for Thunks that load or add
to the program counter. Note that there are no Armv5 Thumb Thunks as there
is no Thumb branch instruction in Armv5 that supports Thunks. These thunks
will not work for Armv4t (arm7tdmi) as this architecture cannot change state
from using the LDR or ADD instruction.

Differential Revision: https://reviews.llvm.org/D50077

llvm-svn: 340160
2018-08-20 09:37:50 +00:00
Peter Smith d1be026ede [ELF] Add support for older Arm Architectures with smaller branch range
The Thumb BL and BLX instructions on older Arm Architectures such as v5 and
v6 have a constrained encoding J1 and J2 must equal 1, later Architectures
relaxed this restriction allowing J1 and J2 to be used to calculate a larger
immediate.

This patch adds support for the old encoding, it is used when the build
attributes for the input objects only contain older architectures.

Differential Revision: https://reviews.llvm.org/D50076

llvm-svn: 340159
2018-08-20 09:19:30 +00:00
Fangrui Song 40a9f2251b [ELF] Replace unused output filenames with /dev/null in tests
Post commit review at rLLD335992

llvm-svn: 336129
2018-07-02 17:48:23 +00:00
Fangrui Song b6772b86e2 [ELF] Move `// REQUIRES:` line to the top
llvm-svn: 335676
2018-06-26 22:20:04 +00:00
Peter Smith 57eb046984 [ELF] Read ARM BuildAttributes section to determine supported features.
lld assumes some ARM features that are not available in all Arm
processors. In particular:
- The blx instruction present for interworking.
- The movt/movw instructions are used in Thunks.
- The J1=1 J2=1 encoding of branch immediates to improve Thumb wide
  branch range are assumed to be present.

This patch reads the ARM Attributes section to check for the
architecture the object file was compiled with. If none of the objects
have an architecture that supports either of these features a warning
will be given. This is most likely to affect armv6 as used in the first
Raspberry Pi.

Differential Revision: https://reviews.llvm.org/D36823

llvm-svn: 319169
2017-11-28 13:51:48 +00:00