This patch adds SubtargetFeatures to LinkGraph. Similar to Triple, some
targets might use this information while linking.
One example, and the reason this patch was written, is linker relaxation
on RISC-V: different relaxations are possible depending on if the C
extension is enabled.
Note that the features are stored as `std::vector<std::string>` to prevent a
public dependency on MC. There is still a private dependency to be able to
convert SubtargetFeatures to a vector.
Reviewed By: lhames
Differential Revision: https://reviews.llvm.org/D149522
We create LinkGraph sections with NoAlloc lifetime now since f05ac803ffe76c7f4299a4e1288cc6bb8b098410
This means we do process debug info sections now with all their relocations. That's ok for the moment.
This first version lays the foundations for AArch32 support in JITLink. ELFLinkGraphBuilder_aarch32 processes REL-type relocations and populates LinkGraphs from ELF object files for both big- and little-endian systems. The ArmCfg member controls subarchitecture-specific details throughout the linking process (i.e. it's passed to ELFJITLinker_aarch32).
Relocation types follow the ABI documentation's division into classes: Data (endian-sensitive), Arm (32-bit little-endian) and Thumb (2x 16-bit little-endian, "Thumb32" in the docs). The implementation of instruction encoding/decoding for relocation resolution is implemented symmetrically and is testable in isolation (see AArch32 category in JITLinkTests).
Callable Thumb functions are marked with a ThumbSymbol target-flag and stored in the LinkGraph with their real addresses. The thumb-bit is added back in when the owning JITDylib requests the address for such a symbol.
The StubsManager can generate (absolute) Thumb-state stubs for branch range extensions on v7+ targets. Proper GOT/PLT handling is not yet implemented.
This patch is based on the backend implementation in ez-clang and has just enough functionality to model the infrastructure and link a Thumb function `main()` that calls `printf()` to dump "Hello Arm!" on Armv7a. It was tested on Raspberry Pi with 32-bit Raspbian OS.
Reviewed By: lhames
Differential Revision: https://reviews.llvm.org/D144083
This first version lays the foundations for AArch32 support in JITLink. ELFLinkGraphBuilder_aarch32 processes REL-type relocations and populates LinkGraphs from ELF object files for both big- and little-endian systems. The ArmCfg member controls subarchitecture-specific details throughout the linking process (i.e. it's passed to ELFJITLinker_aarch32).
Relocation types follow the ABI documentation's division into classes: Data (endian-sensitive), Arm (32-bit little-endian) and Thumb (2x 16-bit little-endian, "Thumb32" in the docs). The implementation of instruction encoding/decoding for relocation resolution is implemented symmetrically and is testable in isolation (see AArch32 category in JITLinkTests).
Callable Thumb functions are marked with a ThumbSymbol target-flag and stored in the LinkGraph with their real addresses. The thumb-bit is added back in when the owning JITDylib requests the address for such a symbol.
The StubsManager can generate (absolute) Thumb-state stubs for branch range extensions on v7+ targets. Proper GOT/PLT handling is not yet implemented.
This patch is based on the backend implementation in ez-clang and has just enough functionality to model the infrastructure and link a Thumb function `main()` that calls `printf()` to dump "Hello Arm!" on Armv7a. It was tested on Raspberry Pi with 32-bit Raspbian OS.
Reviewed By: lhames
Differential Revision: https://reviews.llvm.org/D144083
