[llvm-dev] Loop distribute / versioning to remove control flow

[Sam Parker via llvm-dev]

Hi,


Florian has been working on loop peeling to remove control flow from loop bodies in https://reviews.llvm.org/D43876. For larger constants or other loop invariant bounds, such like:


for (unsigned i = 0; i; i < 1000; ++i) {
  if (i < M)
  ... something
  else
  ... something else
}

The loop could be split into two, like so:

Min = min(1000, M);
unsigned i;
for (i = 0; i; i < Min; ++i) {
    ... something
}

for (; i; i < 1000; ++i) {
    ... something else
}


Both loop distribute and versioning are designed to analyze memory and enable vectorization, but is there much preventing them from being able to split loops to remove control-flow instead? If this seems feasible, could someone give some advice on what would be needed?


Thanks,

sam


Sam Parker

Compilation Tools Engineer | Arm

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Arm.com

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