llvm dev - Feb 2010 - [LLVMdev] RegisterScavenging on targets without subregisters

No, I wasn't having a management lobotomy moment. If the target's
registers
have no subregisters, SubUsed is false and the assert gets tripped.

Ok, back to the original question: What was the original intent in this code
(lines 186-193 in lib/CodeGen/RegisterScavenging.cpp)?


-scooter

On Thu, Feb 25, 2010 at 7:00 PM, Scott Michel <scooter.phd at gmail.com>
wrote:
> Ugh. Management lobotomy kicked in. Need to RTFC better.
>
>
> On Thu, Feb 25, 2010 at 6:18 PM, Scott Michel <scooter.phd at
gmail.com>wrote:
>
>> There's an assert at line 192, lib/CodeGen/RegisterScavenging.cpp
that
>> appears to get tripped on targets that don't have subregisters
defined:
>>
>>         bool SubUsed = false;
>>         for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
>>              unsigned SubReg = *SubRegs; ++SubRegs)
>>           if (isUsed(SubReg)) {
>>             SubUsed = true;
>>             break;
>>           }
>>         assert(SubUsed && "Using an undefined
register!");
>>
>> CellSPU does not define any subregisters; consequently, SubUsed will
>> always be false and trip the assert. What's the intended behavior
(before I
>> submit a bug report)?
>>
>>
>> -scooter
>>
>
>
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Scott Michel skrev:
> No, I wasn't having a management lobotomy moment. If the target's
registers have
> no subregisters, SubUsed is false and the assert gets tripped.
> 
> Ok, back to the original question: What was the original intent in this
code
> (lines 186-193 in lib/CodeGen/RegisterScavenging.cpp)?
You beat me to it :). A simple bypass (patch attached) does at least not 
break 'make check' with x86 and SPU backends. (And fixes the problem 
with call.ll-test breaking when the SPU bigframes patch is applied)

kalle
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Kalle:

Your patch is similar to what I'd coded (and am testing, which means a
couple of hours before I consider committing). Other than cosmetic changes
and changing 'NULL' to '0' (it's an integer list, after
all). This patch now
causes new problems in the CellSPU backend (more stqd's and lqd's), so I
have to investigate those before committing the patch.

'make test' is our friend. 'make test' is our friend. 'make
test' is our
friend. :-)


-scooter

On Thu, Feb 25, 2010 at 11:25 PM, <Kalle.Raiskila at nokia.com> wrote:
>
> Scott Michel skrev:
> > No, I wasn't having a management lobotomy moment. If the
target's
> registers have
> > no subregisters, SubUsed is false and the assert gets tripped.
> >
> > Ok, back to the original question: What was the original intent in
this
> code
> > (lines 186-193 in lib/CodeGen/RegisterScavenging.cpp)?
>
> You beat me to it :). A simple bypass (patch attached) does at least not
> break 'make check' with x86 and SPU backends. (And fixes the
problem
> with call.ll-test breaking when the SPU bigframes patch is applied)
>
> kalle
>
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