case jump table information

Asked May 14 '15 at 05:40

Active May 14 '15 at 05:54

Viewed 422 times

In C/C++ on x86-64, if a switch/case statement is relatively large (more than 3 or 4 entries), a jump table would be generated by LLVM, instead of conditional jump instructions.

In Clang/LLVM, how to export these tables' base, index, and scale information? Program source code is available.

For example, for jmpq *0x400000(,%rbx,8),

How to export the base 0x400000, the index value which will be compared to the value in %rbx, and the scale 8?

edited May 14 '15 at 05:54

asked May 14 '15 at 05:40

WindChaser

Why do you need to deal with this manually in Clang/LLVM? It already handles switch/case statement in a similar fashion. – Nat May 14 '15 at 05:48
I mean exporting these information out for other uses, not to change or add functionalities for LLVM. – WindChaser May 14 '15 at 05:53
you mean this? http://reviews.llvm.org/rL210280 – Nat May 14 '15 at 05:59
It seems info can be got from `llvm/CodeGen/MachineJumpTableInfo.h`, right? – WindChaser May 14 '15 at 06:46
you might need to patch Clang for that. http://reviews.llvm.org/D4128 – Nat May 14 '15 at 06:54

Export C/C++ switch/case jump table information

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