For being able to change subtargets within a compilation unit, among
other things, I need to be able to change the target lowering class that
is used by BasicTTI
For example we have a mips16 and non mips16 version.
On the original call that creates this class, I'd like to pass the
address of the address of the TargetLoweringBase class.
That way I can insert a function pass before this pass which examines
the function attributes and changes the pointer.
So we would get:
ImmutablePass *
llvm::createBasicTargetTransformInfoPass(const TargetLoweringBase **TLI_) {
return new BasicTTI(TLI);
}
we would add the variable
TargetLoweringBase **TLI_
and at the beginning of each pass
TLI = *TLI_;
Maybe there is a more elegant way to do this but this is essentially
what I need to do.
Another way to do this would to be to have a reset virtual function which is passed the Function, and the address of TLI so that it could be modified. This seems somewhat cleaner. The reset virtual function would be added to base class TargetLoweringBase. On 03/22/2013 09:22 AM, reed kotler wrote:> For being able to change subtargets within a compilation unit, among > other things, I need to be able to change the target lowering class that > is used by BasicTTI > > For example we have a mips16 and non mips16 version. > > On the original call that creates this class, I'd like to pass the > address of the address of the TargetLoweringBase class. > > That way I can insert a function pass before this pass which examines > the function attributes and changes the pointer. > > So we would get: > > ImmutablePass * > llvm::createBasicTargetTransformInfoPass(const TargetLoweringBase **TLI_) { > return new BasicTTI(TLI); > } > > we would add the variable > > TargetLoweringBase **TLI_ > > and at the beginning of each pass > > TLI = *TLI_; > > Maybe there is a more elegant way to do this but this is essentially > what I need to do.
Just realized that BasicTransformInfoClass is an immutable pass. Not sure how to reconcile this with fact that there will be different answers needed depending on the subtarget. Seems like BasicTansformInfoClass should become a function pass that does not modify anything. On 03/22/2013 09:43 AM, Reed Kotler wrote:> Another way to do this would to be to have a reset virtual function > which is passed the Function, and the address of TLI so that it could be > modified. > > This seems somewhat cleaner. > > The reset virtual function would be added to base class TargetLoweringBase. > > > On 03/22/2013 09:22 AM, reed kotler wrote: >> For being able to change subtargets within a compilation unit, among >> other things, I need to be able to change the target lowering class that >> is used by BasicTTI >> >> For example we have a mips16 and non mips16 version. >> >> On the original call that creates this class, I'd like to pass the >> address of the address of the TargetLoweringBase class. >> >> That way I can insert a function pass before this pass which examines >> the function attributes and changes the pointer. >> >> So we would get: >> >> ImmutablePass * >> llvm::createBasicTargetTransformInfoPass(const TargetLoweringBase >> **TLI_) { >> return new BasicTTI(TLI); >> } >> >> we would add the variable >> >> TargetLoweringBase **TLI_ >> >> and at the beginning of each pass >> >> TLI = *TLI_; >> >> Maybe there is a more elegant way to do this but this is essentially >> what I need to do.