roastduck commented on a change in pull request #5498:
URL: https://github.com/apache/incubator-tvm/pull/5498#discussion_r421887613
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File path: src/tir/transforms/lower_thread_allreduce.cc
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@@ -330,6 +482,59 @@ class ThreadAllreduceBuilder final : public
StmtExprMutator {
{StringImmNode::make(sync)},
CallNode::Intrinsic));
}
+
+ // Emit warp shuffle intrinsic calls.
+ PrimExpr WarpShuffle(const char* name, Var mask_var, PrimExpr val,
+ int delta_or_lane) {
+ PrimExpr pred = const_true(1);
+ PrimExpr index(0);
+ PrimExpr mask = LoadNode::make(DataType::UInt(32), mask_var, index, pred);
+ PrimExpr width = IntImm(DataType::Int(32), warp_size_);
+ Array<PrimExpr> args{mask, val, IntImm(DataType::Int(32), delta_or_lane),
+ width, width};
+ return CallNode::make(val.dtype(), name, args, CallNode::Intrinsic);
+ }
+
+ // Check if this is a reduction on threadIdx.x and its extent matches
+ // the warp size.
+ //
+ // TODO(tvm-team) reduction with a sub-warp of 8 or 16 threads.
+ bool is_warp_reduction(const std::vector<DataType>& types) const {
+ // Only cuda target supports warp reductions.
+ if (target_->target_name != "cuda") return false;
+
+ // Supported types:
+ // {u}int, {u}long, {u}long long, float, double, half/half2
+ if (std::any_of(types.begin(), types.end(), [](DataType ty) {
+ if (ty.is_float16()) return ty.lanes() > 2;
+ if (ty.is_vector()) return true;
+ return ty.bytes() < 4 || ty.bytes() > 8;
+ })) {
+ return false;
+ }
+ if (thread_extents_.empty()) {
+ return false;
+ }
+
+ const AttrStmtNode* op = thread_extents_.back();
Review comment:
Is the `AttrStmtNode` for reduction axis guaranteed to be the inner most
one? If not, we can't use `back()` here.
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