Beispiel #1
0
// fixFunctionReturns finds 'return' instructions and replaces them
// with appropriate `set pc, $__<name>_epilog` versions.
func fixFunctionReturns(ast *parser.AST, f *parser.Function) {
	var instr *parser.Instruction
	var expr *parser.Expression
	var file, line, col int
	var code []parser.Node
	var ok bool

	name := f.Children()[0].(*parser.Name)
	exitLabel := "$__" + name.Data + "_epilog"
	list := f.Children()[1:]

	for i := range list {
		if instr, ok = list[i].(*parser.Instruction); !ok {
			continue
		}

		code = instr.Children()
		name = code[0].(*parser.Name)
		if name.Data != "return" {
			continue
		}

		file, line, col = instr.File(), instr.Line(), instr.Col()
		name.Data = "set"
		code = append(code, nil, nil)

		expr = parser.NewExpression(file, line, col)
		expr.SetChildren([]parser.Node{
			parser.NewName(file, line, col, "pc"),
		})
		code[1] = expr

		expr = parser.NewExpression(file, line, col)
		expr.SetChildren([]parser.Node{
			parser.NewName(file, line, col, exitLabel),
		})
		code[2] = expr

		instr.SetChildren(code)
	}
}
Beispiel #2
0
// injectFunctionCode injects function prologs and epilogs.
func injectFunctionCode(ast *parser.AST, f *parser.Function) {
	var tmp, code []parser.Node
	var instr *parser.Instruction
	var expr *parser.Expression
	var idx int

	name := f.Children()[0].(*parser.Name)
	exitLabel := "$__" + name.Data + "_epilog"
	file, line, col := name.File(), name.Line(), name.Col()

	// Find list of referenced protected registers.
	var regs []string
	findProtectedRegisters(f.Children()[1:], &regs)

	// Inject prolog and epilog code.
	//
	// For each protected register we found, we add appropriate
	// stack push/pop instructions to preserve their state.
	tmp = make([]parser.Node, len(f.Children())+(len(regs)*2)+2)
	tmp[idx] = parser.NewLabel(file, line, col, name.Data)
	idx++

	// set push, $reg
	for n := range regs {
		instr = parser.NewInstruction(file, line, col)
		code = make([]parser.Node, 3)
		code[0] = parser.NewName(file, line, col, "set")

		expr = parser.NewExpression(file, line, col)
		expr.SetChildren([]parser.Node{
			parser.NewName(file, line, col, "push"),
		})
		code[1] = expr

		expr = parser.NewExpression(file, line, col)
		expr.SetChildren([]parser.Node{
			parser.NewName(file, line, col, regs[n]),
		})
		code[2] = expr

		instr.SetChildren(code)
		tmp[idx] = instr
		idx++
	}

	// Regular code goes here.
	copy(tmp[idx:], f.Children()[1:])
	idx += len(f.Children()) - 1

	// Label denoting the start of the epilog.
	line, col = tmp[idx-1].Line()+1, 1
	tmp[idx] = parser.NewLabel(file, line, col, exitLabel)
	idx++

	// set $reg, pop
	for n := range regs {
		instr = parser.NewInstruction(file, line, col)
		code = make([]parser.Node, 3)
		code[0] = parser.NewName(file, line, col, "set")

		expr = parser.NewExpression(file, line, col)
		expr.SetChildren([]parser.Node{
			parser.NewName(file, line, col, regs[n]),
		})
		code[1] = expr

		expr = parser.NewExpression(file, line, col)
		expr.SetChildren([]parser.Node{
			parser.NewName(file, line, col, "pop"),
		})
		code[2] = expr

		instr.SetChildren(code)
		tmp[idx] = instr
		idx++
	}

	// set pc, pop
	instr = parser.NewInstruction(file, line, col)
	code = make([]parser.Node, 3)
	code[0] = parser.NewName(file, line, col, "set")

	expr = parser.NewExpression(file, line, col)
	expr.SetChildren([]parser.Node{
		parser.NewName(file, line, col, "pc"),
	})
	code[1] = expr

	expr = parser.NewExpression(file, line, col)
	expr.SetChildren([]parser.Node{
		parser.NewName(file, line, col, "pop"),
	})
	code[2] = expr

	instr.SetChildren(code)
	tmp[idx] = instr

	f.SetChildren(tmp)
}