Currently, JT creates and updates local instances of BPI\BFI. As a result global ones have to be invalidated if JT made any changes.
In fact, JT doesn't use any information from BPI/BFI for the sake of the transformation itself. It only creates BPI/BFI to keep them up to date. But since it updates local copies (besides cases when it updates profile metadata) it just waste of time.
Current patch is a rework of D124439. D124439 makes one step and replaces local copies with global ones retrieved through AnalysisPassManager. Here we do one more step and don't create BPI/BFI if the only reason of creation is to keep BPI/BFI up to date. Overall logic is the following. If there is cached BPI/BFI then update it along the transformations. If there is no existing BPI/BFI, then create it only if it is required to update profile metadata.
Please note if BPI/BFI exists on exit from JT (either cached or created) it is always up to date and no reason to invalidate it.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D136827
Currently, JT creates and updates local instances of BPI\BFI. As a result global ones have to be invalidated if JT made any changes.
In fact, JT doesn't use any information from BPI/BFI for the sake of the transformation itself. It only creates BPI/BFI to keep them up to date. But since it updates local copies (besides cases when it updates profile metadata) it just waste of time.
Current patch is a rework of D124439. D124439 makes one step and replaces local copies with global ones retrieved through AnalysisPassManager. Here we do one more step and don't create BPI/BFI if the only reason of creation is to keep BPI/BFI up to date. Overall logic is the following. If there is cached BPI/BFI then update it along the transformations. If there is no existing BPI/BFI, then create it only if it is required to update profile metadata.
Please note if BPI/BFI exists on exit from JT (either cached or created) it is always up to date and no reason to invalidate it.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D136827
Currently, JT creates and updates local instances of BPI\BFI. As a result global ones have to be invalidated if JT made any changes.
In fact, JT doesn't use any information from BPI/BFI for the sake of the transformation itself. It only creates BPI/BFI to keep them up to date. But since it updates local copies (besides cases when it updates profile metadata) it just waste of time.
Current patch is a rework of D124439. D124439 makes one step and replaces local copies with global ones retrieved through AnalysisPassManager. Here we do one more step and don't create BPI/BFI if the only reason of creation is to keep BPI/BFI up to date. Overall logic is the following. If there is cached BPI/BFI then update it along the transformations. If there is no existing BPI/BFI, then create it only if it is required to update profile metadata.
Please note if BPI/BFI exists on exit from JT (either cached or created) it is always up to date and no reason to invalidate it.
Differential Revision: https://reviews.llvm.org/D136827
This patch teaches the jump threading pass to call BPI->eraseBlock
when it folds a conditional branch.
Without this patch, BranchProbabilityInfo could end up with stale edge
probabilities for the basic block containing the conditional branch --
one edge probability with less than 1.0 and the other for a removed
edge.
This patch is one of the steps before we can safely re-apply D91017.
Differential Revision: https://reviews.llvm.org/D91511
This patch removes extraneous calls to setEdgeProbability introduced
in c91487769d80487eba1712a7a172a1c8977a9b4f.
The follow-up patch, a7b662d0f4098371b96ce4446fb0eba79b0b649f, has
since fixed BranchProbabilityInfo::eraseBlock, so we don't need to
worry about getting stale values from getEdgeProbability.
Also, since getEdgeProbability(BB, BB->getSingleSuccessor()) returns
edge probability 1/1 by default for BB with exactly one successor
edge, we don't need to explicitly call setEdgeProbability.
This patch introduces almost no functional change, but we do end up
reducing debug messages from setEdgeProbability.
Differential Revision: https://reviews.llvm.org/D90284
This patch teaches the jump threading pass to set edge probabilities
whenever the pass creates new basic blocks.
Without this patch, the compiler sometimes produces non-deterministic
results. The non-determinism comes from the jump threading pass using
stale edge probabilities in BranchProbabilityInfo. Specifically, when
the jump threading pass creates a new basic block, we don't initialize
its outgoing edge probability.
Edge probabilities are maintained in:
DenseMap<Edge, BranchProbability> Probs;
in class BranchProbabilityInfo, where Edge is an ordered pair of
BasicBlock * and a successor index declared as:
using Edge = std::pair<const BasicBlock *, unsigned>;
Probs maps edges to their corresponding probabilities.
Now, we rarely remove entries from this map, so if we happen to
allocate a new basic block at the same address as a previously deleted
basic block with an edge probability assigned, the newly created basic
block appears to have an edge probability, albeit a stale one.
This patch fixes the problem by explicitly setting edge probabilities
whenever the jump threading pass creates new basic blocks.
Differential Revision: https://reviews.llvm.org/D90106
