This adds support for specialising recursive functions. For example:
int Global = 1;
void recursiveFunc(int *arg) {
if (*arg < 4) {
print(*arg);
recursiveFunc(*arg + 1);
}
}
void main() {
recursiveFunc(&Global);
}
After 3 iterations of function specialisation, followed by inlining of the
specialised versions of recursiveFunc, the main function looks like this:
void main() {
print(1);
print(2);
print(3);
}
To support this, the following has been added:
- Update the solver and state of the new specialised functions,
- An optimisation to propagate constant stack values after each iteration of
function specialisation, which is necessary for the next iteration to
recognise the constant values and trigger.
Specialising recursive functions is (at the moment) controlled by option
-func-specialization-max-iters and is opt-in for compile-time reasons. I.e.,
the default is -func-specialization-max-iters=1, but for the example above we
would need to use -func-specialization-max-iters=3. Future work is to see if we
can increase the default, or improve the cost-model/heuristics to control
compile-times.
Differential Revision: https://reviews.llvm.org/D106426
Now the option is off by default. Since we are not sure if this option
would make the compile time increase aggressively. Although we tested it
on SPEC2017, we may need to test more to make it on by default.
Reviewed By: SjoerdMeijer
Differential Revision: https://reviews.llvm.org/D104365
getSpecializationCost was returning INT_MAX for a case when specialisation
shouldn't happen, but this wasn't properly checked if specialisation was
forced.
Differential Revision: https://reviews.llvm.org/D104461
The original implementation calculating UserBonus uses operator ^, which means XOR in C++
language.
At the first glance of reviewing, I thought it should be power, my bad.
It doesn't make sense to use XOR here. So I believe it should be a
carelessness as I made.
Test Plan: check-all
Reviewed By: SjoerdMeijer
Differential Revision: https://reviews.llvm.org/D104282
