llvm dev - Dec 2009 - [LLVMdev] thumb2 has divide instructions

OK, here's a patch that follows your suggestion.  I'm not an authorized 
developer, so I can't commit it myself.  The test case is also attached
again.

bagel

Jim Grosbach wrote:
 > Ah, ok. I was comparing v7-A and v7-R only. The M3 is described in
 > separate documentation (mostly since it lacks the ARM mode instructions,
 > I suspect). In any case, as far as I can tell, not all v7 processors
 > support the hardware divide instructions.
 >
 > It's definitely desirable to support them for processors which do have
 > them, but they need to be conditionalized such that they're only used
 > when they're available. The instruction predicates are the best way to
 > do that. For now, I would suggest adding a predicate such as
 > "HasThumb2HardwareDivide" and hooking it up to a command line
option to
 > enable (see UseNEONFP in ARMSubTarget.cpp for an example of how to do
 > that). You can then auto-enable it when the CPU string is
"cortex-m3",
 > as is done for the UseNEONFP option on the A8 (see the bottom of the
 > ARMSubtarget::ARMSubtarget() constructor in ARMSubTarget.cpp).
 >
 > Thanks for looking at this!
 >
 > -Jim
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Hello
> OK, here's a patch that follows your suggestion.  I'm not an
authorized
> developer, so I can't commit it myself.  The test case is also attached
> again.
"T2Divide" should be a subtarget feature bit. This way it can be
"automatically" assigned to the procesor.
The instruction selection patterns for t2{S,U}DIV should be also
guarded by this predicate.

Also, for cortex-m3 it will be nice to have separate V7M feature profile.

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

Anton Korobeynikov wrote:
> Hello
> "T2Divide" should be a subtarget feature bit. This way it can be
> "automatically" assigned to the procesor.
I agree this is a better approach.
> The instruction selection patterns for t2{S,U}DIV should be also
> guarded by this predicate.
Is this necessary?  Since the absence of the predicate causes lowering to 
expand divides, the pattern should never show up.
> 
> Also, for cortex-m3 it will be nice to have separate V7M feature profile.
> 
Agreed.  Now how do we get this done?

regards, bagel