From 5ebda89d787af6d27cfde6d9c0f3af13b1270959 Mon Sep 17 00:00:00 2001 From: Ayke van Laethem Date: Sun, 27 Oct 2024 08:44:19 +0100 Subject: runtime: rewrite channel implementation This rewrite simplifies the channel implementation considerably, with 34% less LOC. Perhaps the most important change is the removal of the channel state, which made sense when we had only send and receive operations but only makes things more compliated when multiple select operations can be pending on a single channel. I did this rewrite originally to make it possible to make channels parallelism-safe. The current implementation is not parallelism-safe, but it will be easy to make it so (the main additions will be a channel lock, a global select lock, and an atomic compare-and-swap in chanQueue.pop). --- compiler/channel.go | 37 ++++++++++++++++++++----------------- 1 file changed, 20 insertions(+), 17 deletions(-) (limited to 'compiler/channel.go') diff --git a/compiler/channel.go b/compiler/channel.go index 9969835e8..7e867c278 100644 --- a/compiler/channel.go +++ b/compiler/channel.go @@ -41,17 +41,17 @@ func (b *builder) createChanSend(instr *ssa.Send) { b.CreateStore(chanValue, valueAlloca) } - // Allocate blockedlist buffer. - channelBlockedList := b.getLLVMRuntimeType("channelBlockedList") - channelBlockedListAlloca, channelBlockedListAllocaSize := b.createTemporaryAlloca(channelBlockedList, "chan.blockedList") + // Allocate buffer for the channel operation. + channelOp := b.getLLVMRuntimeType("channelOp") + channelOpAlloca, channelOpAllocaSize := b.createTemporaryAlloca(channelOp, "chan.op") // Do the send. - b.createRuntimeCall("chanSend", []llvm.Value{ch, valueAlloca, channelBlockedListAlloca}, "") + b.createRuntimeCall("chanSend", []llvm.Value{ch, valueAlloca, channelOpAlloca}, "") // End the lifetime of the allocas. // This also works around a bug in CoroSplit, at least in LLVM 8: // https://bugs.llvm.org/show_bug.cgi?id=41742 - b.emitLifetimeEnd(channelBlockedListAlloca, channelBlockedListAllocaSize) + b.emitLifetimeEnd(channelOpAlloca, channelOpAllocaSize) if !isZeroSize { b.emitLifetimeEnd(valueAlloca, valueAllocaSize) } @@ -72,12 +72,12 @@ func (b *builder) createChanRecv(unop *ssa.UnOp) llvm.Value { valueAlloca, valueAllocaSize = b.createTemporaryAlloca(valueType, "chan.value") } - // Allocate blockedlist buffer. - channelBlockedList := b.getLLVMRuntimeType("channelBlockedList") - channelBlockedListAlloca, channelBlockedListAllocaSize := b.createTemporaryAlloca(channelBlockedList, "chan.blockedList") + // Allocate buffer for the channel operation. + channelOp := b.getLLVMRuntimeType("channelOp") + channelOpAlloca, channelOpAllocaSize := b.createTemporaryAlloca(channelOp, "chan.op") // Do the receive. - commaOk := b.createRuntimeCall("chanRecv", []llvm.Value{ch, valueAlloca, channelBlockedListAlloca}, "") + commaOk := b.createRuntimeCall("chanRecv", []llvm.Value{ch, valueAlloca, channelOpAlloca}, "") var received llvm.Value if isZeroSize { received = llvm.ConstNull(valueType) @@ -85,7 +85,7 @@ func (b *builder) createChanRecv(unop *ssa.UnOp) llvm.Value { received = b.CreateLoad(valueType, valueAlloca, "chan.received") b.emitLifetimeEnd(valueAlloca, valueAllocaSize) } - b.emitLifetimeEnd(channelBlockedListAlloca, channelBlockedListAllocaSize) + b.emitLifetimeEnd(channelOpAlloca, channelOpAllocaSize) if unop.CommaOk { tuple := llvm.Undef(b.ctx.StructType([]llvm.Type{valueType, b.ctx.Int1Type()}, false)) @@ -198,10 +198,10 @@ func (b *builder) createSelect(expr *ssa.Select) llvm.Value { if expr.Blocking { // Stack-allocate operation structures. // If these were simply created as a slice, they would heap-allocate. - chBlockAllocaType := llvm.ArrayType(b.getLLVMRuntimeType("channelBlockedList"), len(selectStates)) - chBlockAlloca, chBlockSize := b.createTemporaryAlloca(chBlockAllocaType, "select.block.alloca") - chBlockLen := llvm.ConstInt(b.uintptrType, uint64(len(selectStates)), false) - chBlockPtr := b.CreateGEP(chBlockAllocaType, chBlockAlloca, []llvm.Value{ + opsAllocaType := llvm.ArrayType(b.getLLVMRuntimeType("channelOp"), len(selectStates)) + opsAlloca, opsSize := b.createTemporaryAlloca(opsAllocaType, "select.block.alloca") + opsLen := llvm.ConstInt(b.uintptrType, uint64(len(selectStates)), false) + opsPtr := b.CreateGEP(opsAllocaType, opsAlloca, []llvm.Value{ llvm.ConstInt(b.ctx.Int32Type(), 0, false), llvm.ConstInt(b.ctx.Int32Type(), 0, false), }, "select.block") @@ -209,15 +209,18 @@ func (b *builder) createSelect(expr *ssa.Select) llvm.Value { results = b.createRuntimeCall("chanSelect", []llvm.Value{ recvbuf, statesPtr, statesLen, statesLen, // []chanSelectState - chBlockPtr, chBlockLen, chBlockLen, // []channelBlockList + opsPtr, opsLen, opsLen, // []channelOp }, "select.result") // Terminate the lifetime of the operation structures. - b.emitLifetimeEnd(chBlockAlloca, chBlockSize) + b.emitLifetimeEnd(opsAlloca, opsSize) } else { - results = b.createRuntimeCall("tryChanSelect", []llvm.Value{ + opsPtr := llvm.ConstNull(b.dataPtrType) + opsLen := llvm.ConstInt(b.uintptrType, 0, false) + results = b.createRuntimeCall("chanSelect", []llvm.Value{ recvbuf, statesPtr, statesLen, statesLen, // []chanSelectState + opsPtr, opsLen, opsLen, // []channelOp (nil slice) }, "select.result") } -- cgit v1.2.3