Added relocations to perform function calls with and without passing arguments.
ARM-only, Thumb-only and mixed mode code generations are supported.
Only simple veneers (direct instruction modification) are supported as ARM-Thumb interwork.
Details
Diff Detail
- Repository
- rL LLVM
Event Timeline
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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113 ↗ | (On Diff #18877) | I guess this assert and the one in applyArmReloc are the points where error checking happens. It would be good to use the error checking functionality instead as the asserts will get removed in release builds. |
161 ↗ | (On Diff #18877) | "addressesThumb" is IMO a more descriptive name than "exchanges" so this variable does not help me to read the code. |
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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113 ↗ | (On Diff #18877) | This assert prevents from programmer's mistake when they specify a mask that doesn't correspond to bits in the result. |
161 ↗ | (On Diff #18877) | I also doubted about this name, but I'd like to introduce some variable to point that addressing Thumb (or ARM) code for some instructions means 'exchange instruction set'. Any ideas about better name? |
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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161 ↗ | (On Diff #18877) | switchMode? |
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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161 ↗ | (On Diff #18877) | Thanks! This sounds much better. Will update shortly. |
Calling ARM code from thumb needs a veneer right ?
You would need to create a stub when going through all the atoms if that is the case.
Shankar,
In general case - you're right, the stub is needed to interwork between ARM and Thumb code.
The current implementation covers a subset of the interwork where non-conditional jumps of B/BL forms are used, and they are fixed by changing to BLX instructions (works for ARMv5 and above).
Stub generation should be determined and done in the relocation pass, and it doesn't deny currently implemented instruction fixups, but supplements them.
I'm currently working on the stub generation, but I'd like this part of work with instruction fixups to be accepted. Is it ok?
LGTM with nits.
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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19 ↗ | (On Diff #18883) | Do we need this macro? It would be more readable if we just write uint64_t T = flag; instead of DECLARE_T(flag); |
35 ↗ | (On Diff #18883) | Is this intentional that you used signed integers instead of unsigned integers in this function? I'd use uint16_t when I do bit manipulation. |
170 ↗ | (On Diff #18883) | It's just a suggestion and shouldn't be mixed with this patch, but if you define DEBUG_TYPE like this #define DEBUG_TYPE "ARM" then you can just use DEBUG(...) instead of DEBUG_WITH_TYPE("ARM", ...). |
295 ↗ | (On Diff #18883) | Indentation. |
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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35 ↗ | (On Diff #18883) | I just looked carefully into the code and realized that using signed integers is a proper way of handling addends, because they may be negative numbers as well. |
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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35 ↗ | (On Diff #18883) | I'd think the final result type, which is a signed integer type, can be different from types used for intermediate computation. We shuffle bits by shifts and bitmasks to form a 16 bit pattern here. All intermediate types except the result can be unsigned, no? Looks like all right bit shifts in this function aren't used to extend sign bit. |
lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp | ||
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35 ↗ | (On Diff #18883) | Okay, I'll change all value initialization and intermediate result calculations to operate with unsigned ints of the same size. |