Ejemplo n.º 1
0
// buildFunction takes a function Value, a list of parameters, and a body,
// and generates code for the function.
func (c *compiler) buildFunction(f *LLVMValue, context, params, results *types.Tuple, body *ast.BlockStmt, isvariadic bool) {
	if currblock := c.builder.GetInsertBlock(); !currblock.IsNil() {
		defer c.builder.SetInsertPointAtEnd(currblock)
	}
	llvm_fn := llvm.ConstExtractValue(f.LLVMValue(), []uint32{0})
	entry := llvm.AddBasicBlock(llvm_fn, "entry")
	c.builder.SetInsertPointAtEnd(entry)

	// For closures, context is the captured context values.
	var paramoffset int
	if context != nil {
		paramoffset++

		// Store the existing values. We're going to temporarily
		// replace the values with offsets into the context param.
		oldvalues := make([]*LLVMValue, context.Len())
		for i := range oldvalues {
			v := context.At(i)
			oldvalues[i] = c.objectdata[v].Value
		}
		defer func() {
			for i := range oldvalues {
				v := context.At(i)
				c.objectdata[v].Value = oldvalues[i]
			}
		}()

		// The context parameter is a pointer to a struct
		// whose elements are pointers to captured values.
		arg0 := llvm_fn.Param(0)
		for i := range oldvalues {
			v := context.At(i)
			argptr := c.builder.CreateStructGEP(arg0, i, "")
			argptr = c.builder.CreateLoad(argptr, "")
			ptrtyp := oldvalues[i].pointer.Type()
			newvalue := c.NewValue(argptr, ptrtyp)
			c.objectdata[v].Value = newvalue.makePointee()
		}
	}

	// Bind receiver, arguments and return values to their
	// identifiers/objects. We'll store each parameter on the stack so
	// they're addressable.
	nparams := int(params.Len())
	for i := 0; i < nparams; i++ {
		v := params.At(i)
		name := v.Name()
		if name != "" {
			value := llvm_fn.Param(i + paramoffset)
			typ := v.Type()
			if isvariadic && i == nparams-1 {
				typ = types.NewSlice(typ)
			}
			stackvalue := c.builder.CreateAlloca(c.types.ToLLVM(typ), name)
			c.builder.CreateStore(value, stackvalue)
			ptrvalue := c.NewValue(stackvalue, types.NewPointer(typ))
			stackvar := ptrvalue.makePointee()
			stackvar.stack = f
			c.objectdata[v].Value = stackvar
		}
	}

	funcstate := &function{LLVMValue: f, results: results}
	c.functions.push(funcstate)
	hasdefer := hasDefer(funcstate, body)

	// Allocate space on the stack for named results.
	results.ForEach(func(v *types.Var) {
		name := v.Name()
		allocstack := name != ""
		if !allocstack && hasdefer {
			c.objectdata[v] = &ObjectData{}
			allocstack = true
		}
		if allocstack {
			typ := v.Type()
			llvmtyp := c.types.ToLLVM(typ)
			stackptr := c.builder.CreateAlloca(llvmtyp, name)
			c.builder.CreateStore(llvm.ConstNull(llvmtyp), stackptr)
			ptrvalue := c.NewValue(stackptr, types.NewPointer(typ))
			stackvar := ptrvalue.makePointee()
			stackvar.stack = f
			c.objectdata[v].Value = stackvar
		}
	})

	// Create the function body.
	if hasdefer {
		c.makeDeferBlock(funcstate, body)
	}
	c.VisitBlockStmt(body, false)
	c.functions.pop()

	// If the last instruction in the function is not a terminator, then
	// we either have unreachable code or a missing optional return statement
	// (the latter case is allowable only for functions without results).
	//
	// Use GetInsertBlock rather than LastBasicBlock, since the
	// last basic block might actually be a "defer" block.
	last := c.builder.GetInsertBlock()
	if in := last.LastInstruction(); in.IsNil() || in.IsATerminatorInst().IsNil() {
		c.builder.SetInsertPointAtEnd(last)
		if results.Len() == 0 {
			if funcstate.deferblock.IsNil() {
				c.builder.CreateRetVoid()
			} else {
				c.builder.CreateBr(funcstate.deferblock)
			}
		} else {
			c.builder.CreateUnreachable()
		}
	}
}