compiler: add support for channel operations

Support for channels is not complete. The following pieces are missing:

  * Channels with values bigger than int. An int in TinyGo can always
    contain at least a pointer, so pointers are okay to send.
  * Buffered channels.
  * The select statement.

compiler/channel.go

@@ -0,0 +1,97 @@
+package compiler
+
+// This file lowers channel operations (make/send/recv/close) to runtime calls
+// or pseudo-operations that are lowered during goroutine lowering.
+
+import (
+	"go/types"
+
+	"github.com/aykevl/go-llvm"
+	"golang.org/x/tools/go/ssa"
+)
+
+// emitMakeChan returns a new channel value for the given channel type.
+func (c *Compiler) emitMakeChan(expr *ssa.MakeChan) (llvm.Value, error) {
+	valueType, err := c.getLLVMType(expr.Type().(*types.Chan).Elem())
+	if err != nil {
+		return llvm.Value{}, err
+	}
+	if c.targetData.TypeAllocSize(valueType) > c.targetData.TypeAllocSize(c.intType) {
+		// Values bigger than int overflow the data part of the coroutine.
+		// TODO: make the coroutine data part big enough to hold these bigger
+		// values.
+		return llvm.Value{}, c.makeError(expr.Pos(), "todo: channel with values bigger than int")
+	}
+	chanType := c.mod.GetTypeByName("runtime.channel")
+	size := c.targetData.TypeAllocSize(chanType)
+	sizeValue := llvm.ConstInt(c.uintptrType, size, false)
+	ptr := c.createRuntimeCall("alloc", []llvm.Value{sizeValue}, "chan.alloc")
+	ptr = c.builder.CreateBitCast(ptr, llvm.PointerType(chanType, 0), "chan")
+	return ptr, nil
+}
+
+// emitChanSend emits a pseudo chan send operation. It is lowered to the actual
+// channel send operation during goroutine lowering.
+func (c *Compiler) emitChanSend(frame *Frame, instr *ssa.Send) error {
+	valueType, err := c.getLLVMType(instr.Chan.Type().(*types.Chan).Elem())
+	if err != nil {
+		return err
+	}
+	ch, err := c.parseExpr(frame, instr.Chan)
+	if err != nil {
+		return err
+	}
+	chanValue, err := c.parseExpr(frame, instr.X)
+	if err != nil {
+		return err
+	}
+	valueSize := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(chanValue.Type()), false)
+	valueAlloca := c.builder.CreateAlloca(valueType, "chan.value")
+	c.builder.CreateStore(chanValue, valueAlloca)
+	valueAllocaCast := c.builder.CreateBitCast(valueAlloca, c.i8ptrType, "chan.value.i8ptr")
+	c.createRuntimeCall("chanSendStub", []llvm.Value{llvm.Undef(c.i8ptrType), ch, valueAllocaCast, valueSize}, "")
+	return nil
+}
+
+// emitChanRecv emits a pseudo chan receive operation. It is lowered to the
+// actual channel receive operation during goroutine lowering.
+func (c *Compiler) emitChanRecv(frame *Frame, unop *ssa.UnOp) (llvm.Value, error) {
+	valueType, err := c.getLLVMType(unop.X.Type().(*types.Chan).Elem())
+	if err != nil {
+		return llvm.Value{}, err
+	}
+	valueSize := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(valueType), false)
+	ch, err := c.parseExpr(frame, unop.X)
+	if err != nil {
+		return llvm.Value{}, err
+	}
+	valueAlloca := c.builder.CreateAlloca(valueType, "chan.value")
+	valueAllocaCast := c.builder.CreateBitCast(valueAlloca, c.i8ptrType, "chan.value.i8ptr")
+	valueOk := c.builder.CreateAlloca(c.ctx.Int1Type(), "chan.comma-ok.alloca")
+	c.createRuntimeCall("chanRecvStub", []llvm.Value{llvm.Undef(c.i8ptrType), ch, valueAllocaCast, valueOk, valueSize}, "")
+	received := c.builder.CreateLoad(valueAlloca, "chan.received")
+	if unop.CommaOk {
+		commaOk := c.builder.CreateLoad(valueOk, "chan.comma-ok")
+		tuple := llvm.Undef(c.ctx.StructType([]llvm.Type{valueType, c.ctx.Int1Type()}, false))
+		tuple = c.builder.CreateInsertValue(tuple, received, 0, "")
+		tuple = c.builder.CreateInsertValue(tuple, commaOk, 1, "")
+		return tuple, nil
+	} else {
+		return received, nil
+	}
+}
+
+// emitChanClose closes the given channel.
+func (c *Compiler) emitChanClose(frame *Frame, param ssa.Value) error {
+	valueType, err := c.getLLVMType(param.Type().(*types.Chan).Elem())
+	valueSize := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(valueType), false)
+	if err != nil {
+		return err
+	}
+	ch, err := c.parseExpr(frame, param)
+	if err != nil {
+		return err
+	}
+	c.createRuntimeCall("chanClose", []llvm.Value{ch, valueSize}, "")
+	return nil
+}