Added simple variable lifetimes

src/build/Function.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"strconv"
 
+	"git.akyoto.dev/cli/q/src/build/arch/x64"
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 	"git.akyoto.dev/cli/q/src/build/expression"
@@ -141,17 +142,51 @@ func (f *Function) ExpressionToRegister(root *expression.Expression, register cp
 
 // ExpressionsToRegisters moves multiple expressions into the specified registers.
 func (f *Function) ExpressionsToRegisters(expressions []*expression.Expression, registers []cpu.Register) error {
+	var destinations []cpu.Register
+
 	for i := len(expressions) - 1; i >= 0; i-- {
-		err := f.ExpressionToRegister(expressions[i], registers[i])
+		original := registers[i]
+		expression := expressions[i]
+
+		if expression.IsLeaf() {
+			variable, exists := f.Variables[expression.Token.Text()]
+
+			if exists && variable.Register == original {
+				continue
+			}
+		}
+
+		register := original
+		save := !f.CPU.IsFree(register)
+
+		if save {
+			register = x64.RAX
+		}
+
+		err := f.ExpressionToRegister(expression, register)
 
 		if err != nil {
 			return err
 		}
+
+		if save {
+			destinations = append(destinations, original)
+			f.Assembler.Register(asm.PUSH, x64.RAX)
+		}
+	}
+
+	for i := len(destinations) - 1; i >= 0; i-- {
+		f.Assembler.Register(asm.POP, destinations[i])
 	}
 
 	return nil
 }
 
+func (f *Function) Log(messages ...any) {
+	fmt.Printf("[%s] ", f.Name)
+	fmt.Println(messages...)
+}
+
 // TokenToRegister moves a token into a register.
 // It only works with identifiers, numbers and strings.
 func (f *Function) TokenToRegister(t token.Token, register cpu.Register) error {
@@ -168,6 +203,7 @@ func (f *Function) TokenToRegister(t token.Token, register cpu.Register) error {
 			f.Assembler.RegisterRegister(asm.MOVE, register, variable.Register)
 		}
 
+		f.useVariable(variable)
 		return nil
 
 	case token.Number: