[llvm-dev] LLVM Block is not the basic block

[Krzysztof Parzyszek via llvm-dev]

It doesn't seem that LLVM treats non-returning calls in any special way 
in the LLVM IR.

You could probably write your own pass that splits basic blocks at each 
call, but there are optimizations that would merge the pieces back 
together. If you do the splitting at the right moment, it may work, but 
it really depends on your specific application.

-Krzysztof

On 5/29/2018 8:49 AM, Muhui Jiang wrote:
> Hi Krzysztof
> 
> I see and I agree with your explanation
> 
> However, you know some start of art binary analysis tools like angr will 
> accept LLVM's such kind of design. You know there are some non-return 
> functions. Does LLVM consider this?  Do you have any ideas if I want to 
> create a block that cannot contain function calls with LLVM IR.
> 
> Regards
> Muhui
> 
> 2018-05-29 21:20 GMT+08:00 Krzysztof Parzyszek via llvm-dev 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>:
> 
>     On 5/29/2018 7:59 AM, Muhui Jiang via llvm-dev wrote:
> 
>         So the reason why basic blocks can contain function calls is
>         because of code inlining?
> 
> 
>     Not really. Basic blocks are units of code in a context of a
>     specific function. When execution reaches a function call, it will
>     go outside of the current function for some time, but then it will
>     return back to the instruction following the call. From the
>     perspective of the function containing the call, the call is simply
>     another (potentially complicated and long-running) instruction.
>     Generally speaking, a basic block ends at instruction A, if the
>     instruction following A is not guaranteed to execute after A has
>     executed. From the point of view of a given function, a call to
>     another function will return back to the caller, so logically there
>     is no reason to terminate the basic block at a call. There are of
>     course complications, like calls that can throw exceptions, or calls
>     that don't return, but the general idea is that calls do return.
> 
>     -Krzysztof
> 
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> 

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