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Merged
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Sep 22, 2022
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JIT: improve scalability of optReachable #75990

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2 changes: 2 additions & 0 deletions src/coreclr/jit/compiler.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6980,6 +6980,8 @@ class Compiler
bool optRedundantBranch(BasicBlock* const block);
bool optJumpThread(BasicBlock* const block, BasicBlock* const domBlock, bool domIsSameRelop);
bool optReachable(BasicBlock* const fromBlock, BasicBlock* const toBlock, BasicBlock* const excludedBlock);
BitVecTraits* optReachableBitVecTraits;
BitVec optReachableBitVec;
void optRelopImpliesRelop(RelopImplicationInfo* rii);

/**************************************************************************
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23 changes: 12 additions & 11 deletions src/coreclr/jit/redundantbranchopts.cpp
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Expand Up @@ -74,16 +74,10 @@ PhaseStatus Compiler::optRedundantBranches()
}
};

optReachableBitVecTraits = nullptr;
OptRedundantBranchesDomTreeVisitor visitor(this);
visitor.WalkTree();

// Reset visited flags, in case we set any.
//
for (BasicBlock* const block : Blocks())
{
block->bbFlags &= ~BBF_VISITED;
}

#if DEBUG
if (verbose && visitor.madeChanges)
{
Expand Down Expand Up @@ -1593,9 +1587,15 @@ bool Compiler::optReachable(BasicBlock* const fromBlock, BasicBlock* const toBlo
return true;
}

for (BasicBlock* const block : Blocks())
if (optReachableBitVecTraits == nullptr)
{
block->bbFlags &= ~BBF_VISITED;
optReachableBitVecTraits = new (this, CMK_Reachability) BitVecTraits(fgBBNumMax + 1, this);
optReachableBitVec = BitVecOps::MakeEmpty(optReachableBitVecTraits);
}
else
{
assert(BitVecTraits::GetSize(optReachableBitVecTraits) == fgBBNumMax + 1);
BitVecOps::ClearD(optReachableBitVecTraits, optReachableBitVec);
}

ArrayStack<BasicBlock*> stack(getAllocator(CMK_Reachability));
Expand All @@ -1604,7 +1604,6 @@ bool Compiler::optReachable(BasicBlock* const fromBlock, BasicBlock* const toBlo
while (!stack.Empty())
{
BasicBlock* const nextBlock = stack.Pop();
nextBlock->bbFlags |= BBF_VISITED;
assert(nextBlock != toBlock);

if (nextBlock == excludedBlock)
Expand All @@ -1619,11 +1618,13 @@ bool Compiler::optReachable(BasicBlock* const fromBlock, BasicBlock* const toBlo
return true;
}

if ((succ->bbFlags & BBF_VISITED) != 0)
if (BitVecOps::IsMember(optReachableBitVecTraits, optReachableBitVec, succ->bbNum))
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We have this exact code in fgRemoveDeadBlocks(). Can we unify them?

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That version uses BlockSet, which I'm avoiding here because it is epoch sensitive.

In general, it would be nice to have the ability to represent (sparse) block sets that are independent of bbNum and not fixed capacity so that they can persist for longer stretches or be reused as general scratch sets, but we don't have anything like that yet.

{
continue;
}

BitVecOps::AddElemD(optReachableBitVecTraits, optReachableBitVec, succ->bbNum);

stack.Push(succ);
}
}
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3 changes: 0 additions & 3 deletions src/tests/issues.targets
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Expand Up @@ -51,9 +51,6 @@
<ExcludeList Include="$(XunitTestBinBase)/readytorun/r2rdump/BasicTests/R2RDumpTest/*">
<Issue>https://github.com/dotnet/runtime/issues/10888 https://github.com/dotnet/runtime/issues/11823 </Issue>
</ExcludeList>
<ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/DevDiv_255294/DevDiv_255294/*">
<Issue>https://github.com/dotnet/runtime/issues/44341</Issue>
</ExcludeList>
<ExcludeList Include="$(XunitTestBinBase)/JIT/Directed/rvastatics/RVAOrderingTest/*">
<Issue>https://github.com/dotnet/runtime/issues/55966</Issue>
</ExcludeList>
Expand Down