[BOLT] Make instruction size a first-class annotation #72167
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When NOP instructions are used to reserve space in the code, e.g. for patching, it becomes critical to preserve their original size while emitting the code. On x86, we rely on "Size" annotation for NOP instructions size, as the original instruction size is lost in the disassembly/assembly process. This change makes instruction size a first-class annotation and is affectively NFCI. A follow-up diff will use the annotation for code emission.
aaupov
approved these changes
Nov 13, 2023
|
Do you think it will have any impact on BOLT's max RSS? If so, it would make sense to enable llvm/llvm-zorg#70 |
If there is, there will be a negligible reduction in max RSS. |
zahiraam
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Nov 20, 2023
When NOP instructions are used to reserve space in the code, e.g. for patching, it becomes critical to preserve their original size while emitting the code. On x86, we rely on "Size" annotation for NOP instructions size, as the original instruction size is lost in the disassembly/assembly process. This change makes instruction size a first-class annotation and is affectively NFCI. A follow-up diff will use the annotation for code emission.
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When NOP instructions are used to reserve space in the code, e.g. for patching, it becomes critical to preserve their original size while emitting the code. On x86, we rely on "Size" annotation for NOP instructions size, as the original instruction size is lost in the disassembly/assembly process.
This change makes instruction size a first-class annotation and is affectively NFCI. A follow-up diff will use the annotation for code emission.