neo-go/pkg/vm/compiler/func_scope.go

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package compiler
import (
"go/ast"
)
// A funcScope represents the scope within the function context.
// It holds al the local variables along with the initialized struct positions.
type funcScope struct {
// identifier of the function.
name string
// Selector of the function if there is any. Only functions imported
// from other packages should have a selector.
selector *ast.Ident
// The declaration of the function in the AST. Nil if this scope is not a function.
decl *ast.FuncDecl
// Program label of the scope
label int
// Local variables
locals map[string]int
// voidCalls are basically functions that return their value
// into nothing. The stack has their return value but there
// is nothing that consumes it. We need to keep track of
// these functions so we can cleanup (drop) the returned
// value from the stack. We also need to add every voidCall
// return value to the stack size.
voidCalls map[*ast.CallExpr]bool
// local variable counter
i int
}
func newFuncScope(decl *ast.FuncDecl, label int) *funcScope {
return &funcScope{
name: decl.Name.Name,
decl: decl,
label: label,
locals: map[string]int{},
voidCalls: map[*ast.CallExpr]bool{},
i: -1,
}
}
// analyzeVoidCalls will check for functions that are not assigned
// and therefore we need to cleanup the return value from the stack.
func (c *funcScope) analyzeVoidCalls(node ast.Node) bool {
switch n := node.(type) {
case *ast.AssignStmt:
for i := 0; i < len(n.Rhs); i++ {
switch n.Rhs[i].(type) {
case *ast.CallExpr:
return false
}
}
case *ast.ReturnStmt:
switch n.Results[0].(type) {
case *ast.CallExpr:
return false
}
case *ast.BinaryExpr:
return false
case *ast.CallExpr:
c.voidCalls[n] = true
return false
}
return true
}
func (c *funcScope) stackSize() int64 {
size := 0
ast.Inspect(c.decl, func(n ast.Node) bool {
switch n := n.(type) {
case *ast.AssignStmt:
size += len(n.Rhs)
case *ast.ReturnStmt, *ast.IfStmt:
size++
// This handles the inline GenDecl like "var x = 2"
case *ast.GenDecl:
switch t := n.Specs[0].(type) {
case *ast.ValueSpec:
if len(t.Values) > 0 {
size++
}
}
}
return true
})
numArgs := len(c.decl.Type.Params.List)
// Also take care of struct methods recv: e.g. (t Token).Foo().
if c.decl.Recv != nil {
numArgs += len(c.decl.Recv.List)
}
return int64(size + numArgs + len(c.voidCalls))
}
// newLocal creates a new local variable into the scope of the function.
func (c *funcScope) newLocal(name string) int {
c.i++
c.locals[name] = c.i
return c.i
}
// loadLocal loads the position of a local variable inside the scope of the function.
func (c *funcScope) loadLocal(name string) int {
i, ok := c.locals[name]
if !ok {
// should emit a compiler warning.
return c.newLocal(name)
}
return i
}