Make sure every conditional branch constructed by `LoopUnrollRuntime`
code sets branch weights.
- Add new 1:127 weights for the conditional jumps checking whether the
whole (unrolled) loop should be skipped in the generated prolog or
epilog code.
- Remove `updateLatchBranchWeightsForRemainderLoop` function and just
add weights immediately when constructing the relevant branches. This
leads to simpler code and makes the code more obvious as every call
to `CreateCondBr` now has a `BranchWeights` parameter.
- Rework formula for epilogue latch weights, to assume equal
distribution of remainders and remove `assert` (as I was able to
reach this code when forcing small unroll factors on the commandline).
Differential Revision: https://reviews.llvm.org/D158642
CallInst::updateProfWeight() creates branch_weights with i64 instead of i32.
To be more consistent everywhere and remove lots of casts from uint64_t
to uint32_t, use i64 for branch_weights.
Reviewed By: davidxl
Differential Revision: https://reviews.llvm.org/D88609
CallInst::updateProfWeight() creates branch_weights with i64 instead of i32.
To be more consistent everywhere and remove lots of casts from uint64_t
to uint32_t, use i64 for branch_weights.
Reviewed By: davidxl
Differential Revision: https://reviews.llvm.org/D88609
Unrolling a loop with compile-time unknown trip count results in a remainder loop. The remainder loop executes the remaining iterations of the original loop when the original trip count is not a multiple of the unroll factor. For better profile counts maintenance throughout the optimization pipeline, I'm assigning an artificial weight to the latch branch of the remainder loop.
A remainder loop runs up to as many times as the unroll factor subtracted by 1. Therefore I'm assigning the maximum possible trip count as the back edge weight. This should be more accurate than the default non-profile weight, which assumes the back edge runs much more frequently than the exit edge.
Differential Revision: https://reviews.llvm.org/D83187
