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make continuation-style barrier removal support nested parallel 

Only the innermost scf.parallel is allowed to contain barrier though.
Otherwise, we need a mechanism to recursively create local CFGs and
inline them into parent regions.
This commit is contained in:
Alex Zinenko 2021-08-30 19:05:36 +02:00 committed by William Moses
parent b570c7b115
commit acc2bd3f83
1 changed files with 30 additions and 9 deletions
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39
lib/polygeist/Passes/BarrierRemovalContinuation.cpp
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@ -32,10 +32,8 @@ using namespace polygeist;
/// Returns true if the given parallel op has a nested barrier op that is not
/// nested in some other parallel op.
static bool hasImmediateBarriers(scf::ParallelOp op) {
WalkResult result = op.walk([](Operation *nested) {
if (isa<scf::ParallelOp>(nested))
return WalkResult::skip();
if (isa<polygeist::BarrierOp>(nested))
WalkResult result = op.walk([op](polygeist::BarrierOp barrier) {
if (barrier->getParentOfType<scf::ParallelOp>() == op)
return WalkResult::interrupt();
return WalkResult::advance();
});
@ -110,9 +108,16 @@ static void splitBlocksWithBarrier(Region &region) {
/// function.
static LogicalResult splitBlocksWithBarrier(FuncOp function) {
WalkResult result = function.walk([](scf::ParallelOp op) -> WalkResult {
if (op->getParentOfType<scf::ParallelOp>())
if (!hasImmediateBarriers(op))
return success();
if (op->walk([op](scf::ParallelOp nested) {
return op == nested ? WalkResult::advance()
: WalkResult::interrupt();
}).wasInterrupted()) {
return op->emitError() << "nested parallel ops with barriers not "
"supported (consider outlining)";
}
splitBlocksWithBarrier(
cast<scf::ExecuteRegionOp>(&op.getBody()->front()).region());
@ -367,6 +372,19 @@ findInsertionPointAfterLoopOperands(scf::ParallelOp op) {
/// iteration writing a different element.
static void reg2mem(ArrayRef<llvm::SetVector<Block *>> subgraphs,
scf::ParallelOp parallel) {
// Check if a block exists in another subgraph than the given subgraph (there
// may be duplicates).
auto otherSubgraphContains = [&](const llvm::SetVector<Block *> &subgraph,
Block *block) {
for (const llvm::SetVector<Block *> &other : subgraphs) {
if (&other == &subgraph)
continue;
if (other.contains(block))
return true;
}
return false;
};
// Find all values that are defined in one subgraph and used in another
// subgraph. These will have to be communicated through memory.
SmallVector<Value> valuesToStore;
@ -374,7 +392,7 @@ static void reg2mem(ArrayRef<llvm::SetVector<Block *>> subgraphs,
const llvm::SetVector<Block *> &subgraph) {
for (Value value : values) {
for (Operation *user : value.getUsers()) {
if (!subgraph.contains(user->getBlock())) {
if (otherSubgraphContains(subgraph, user->getBlock())) {
valuesToStore.push_back(value);
return;
}
@ -457,9 +475,9 @@ static void reg2mem(ArrayRef<llvm::SetVector<Block *>> subgraphs,
/// // ^bb1
/// ^bb0:
/// br ^bb1
/// // only the original entry block, which remains the entry block,
/// // will have block arguments that correspond to old loop IVs
/// // replace all uses of those with new IVs and drop them
/// // only the original entry block will have block arguments that
/// // correspond to old loop IVs replace all uses of those with new
/// // IVs and drop them
/// ^bb1:
/// condbr .. ^bb2, ^bb3
/// ^bb2:
@ -541,6 +559,9 @@ static void createContinuations(FuncOp func) {
OpBuilder allocaBuilder(&func.body().front(), func.body().front().begin());
func.walk([&](scf::ParallelOp parallel) {
// Ignore parallel ops with no barriers.
if (!hasImmediateBarriers(parallel))
return;
Value storage = allocaBuilder.create<memref::AllocaOp>(
parallel.getLoc(), MemRefType::get({}, allocaBuilder.getIndexType()));
createContinuations(parallel, storage);