Greg is right that this was a libedis feature and has no equivalent in
LLDB today.
MCInst, however, doesn't have enough information by itself to do this.
The reason is that for many things that are considered "operands," the
MCInst has several underlying operands. For example, an operand that
was expressed as a register + an offset would be represented in MCInst
as a register operand and in immediate operand, and only correlating the
opcode with the LLVM instruction tables (and possibly some special
knowledge) would tell you that the two belong together.
Additionally, libedis could express the semantics of the instruction
operands (e.g., "this is a source operand and represents the result of
dereferncing rbp - 4") , and inform the client what ranges of characters
in the generated string represented each high level operand. Both of
these features are not exposed anywhere at the moment, and in fact the
underlying knowledge was lost when the edis TableGen backend was deprecated.
There are a few LLDB features that reads instructions and attempt to
interpret them:
* The fast unwinder looks for specific bit patterns (see
UnwindAssembly_x86::GetFastUnwindPlan in UnwindAssembly-x86.cpp);
* The ARM instruction emulator has its own home-grown instruction
table (see EmulateInstructionARM64.cpp); and
* The crash diagnose functionality actually parses the output strings
from the disassembler (see DoGuessValueAt in StackFrame.cpp).
Sean
On 8/31/17 11:09 AM, Greg Clayton via lldb-dev wrote:
I believe libedis was deprecated many years ago and hasn't returned.
We use the standard LLVM disassembler, so any features need to be
built into llvm::MCInst.
On Aug 31, 2017, at 10:42 AM, Tatyana Krasnukha via lldb-dev
<lldb-dev@lists.llvm.org <mailto:lldb-dev@lists.llvm.org>> wrote:
Hello,
As I understand it, old disassembler (based on libedis) could print
symbolic information instead/beside address operand of an
instruction. And it looks like there is not such ability in
disassembler now. Is thisresponsibility shifted on some other
component of lldb? Or it was considered as useless and was removed at
all?
Thanks,
Tatyana
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