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123 lines
2.9 KiB
Go
123 lines
2.9 KiB
Go
package compiler
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import (
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"go/ast"
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"go/token"
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)
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// A funcScope represents the scope within the function context.
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// It holds al the local variables along with the initialized struct positions.
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type funcScope struct {
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// Identifier of the function.
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name string
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// Selector of the function if there is any. Only functions imported
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// from other packages should have a selector.
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selector *ast.Ident
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// The declaration of the function in the AST. Nil if this scope is not a function.
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decl *ast.FuncDecl
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// Program label of the scope
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label uint16
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// Range of opcodes corresponding to the function.
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rng DebugRange
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// Local variables
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locals map[string]int
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// voidCalls are basically functions that return their value
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// into nothing. The stack has their return value but there
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// is nothing that consumes it. We need to keep track of
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// these functions so we can cleanup (drop) the returned
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// value from the stack. We also need to add every voidCall
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// return value to the stack size.
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voidCalls map[*ast.CallExpr]bool
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// Local variable counter.
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i int
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}
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func newFuncScope(decl *ast.FuncDecl, label uint16) *funcScope {
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return &funcScope{
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name: decl.Name.Name,
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decl: decl,
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label: label,
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locals: map[string]int{},
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voidCalls: map[*ast.CallExpr]bool{},
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i: -1,
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}
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}
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// analyzeVoidCalls checks for functions that are not assigned
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// and therefore we need to cleanup the return value from the stack.
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func (c *funcScope) analyzeVoidCalls(node ast.Node) bool {
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switch n := node.(type) {
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case *ast.AssignStmt:
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for i := 0; i < len(n.Rhs); i++ {
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switch n.Rhs[i].(type) {
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case *ast.CallExpr:
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return false
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}
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}
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case *ast.ReturnStmt:
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switch n.Results[0].(type) {
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case *ast.CallExpr:
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return false
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}
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case *ast.BinaryExpr:
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return false
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case *ast.CallExpr:
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c.voidCalls[n] = true
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return false
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}
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return true
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}
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func (c *funcScope) stackSize() int64 {
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size := 0
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ast.Inspect(c.decl, func(n ast.Node) bool {
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switch n := n.(type) {
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case *ast.AssignStmt:
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if n.Tok == token.DEFINE {
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size += len(n.Rhs)
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}
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case *ast.ReturnStmt, *ast.IfStmt:
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size++
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// This handles the inline GenDecl like "var x = 2"
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case *ast.GenDecl:
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switch t := n.Specs[0].(type) {
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case *ast.ValueSpec:
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if len(t.Values) > 0 {
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size++
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}
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}
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}
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return true
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})
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numArgs := len(c.decl.Type.Params.List)
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// Also take care of struct methods recv: e.g. (t Token).Foo().
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if c.decl.Recv != nil {
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numArgs += len(c.decl.Recv.List)
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}
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return int64(size + numArgs + len(c.voidCalls))
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}
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// newLocal creates a new local variable into the scope of the function.
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func (c *funcScope) newLocal(name string) int {
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c.i++
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c.locals[name] = c.i
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return c.i
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}
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// loadLocal loads the position of a local variable inside the scope of the function.
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func (c *funcScope) loadLocal(name string) int {
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i, ok := c.locals[name]
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if !ok {
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// should emit a compiler warning.
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return c.newLocal(name)
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}
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return i
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}
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