[LLVMdev] Problem with isMoveInstr

[Alkis Evlogimenos]

On Thu, 2004-07-01 at 09:26, Vladimir Prus wrote:
> I've tried to implement the isMoveInstr method from TargetInstrInfo class, and 
> the register allocator immediately started to crash, in:
> 
> #4  0x40e88787 in llvm::LiveIntervals::joinIntervals (this=0x80630b0)
>     at ../lib/CodeGen/LiveIntervals.cpp:493
> 493                     assert(r2iA != r2iMap_.end());
> 
> The instruction it crashes is:
> 
> (gdb) p $4.dump()
>   %reg1056 = move %gr7
> 
> And gr7 is exactly the register which is looked up with
> 
>    Reg2IntervalMap::iterator r2iA = r2iMap_.find(regA)
> 
> on line 492. I'm not sure the about the logic, but seems the code tries to map 
> register into live interval, and since the above gr7 is inserted by code 
> selector (it's return value from a function), it's not wonder no interval is 
> found.

You are right that it looks for the intervals for the register. But,
there should be an interval for gr7 as well. Is it defined somewhere
before that? Can you show some of the code before the use if gr7?

> I've worked this around by making isMoveInstr return false when either of 
> operands is physical register, but looks like this defeats the purpose of 
> isMoveInstr. What kind of information I can further provide to help diagnose 
> the problem?

Make sure gr7 is defined somewhere in the basic block the move belongs
to. If you still see the crash it would be nice to see the interval for
gr7 and the debug output of regalloc using -debug-only=regalloc.

-- 

Alkis