Implemented return values

src/build/SaveRegister.go

@@ -0,0 +1,37 @@
+package build
+
+import (
+	"git.akyoto.dev/cli/q/src/build/asm"
+	"git.akyoto.dev/cli/q/src/build/cpu"
+)
+
+// SaveRegister attempts to move a variable occupying this register to another register.
+func (f *Function) SaveRegister(register cpu.Register) {
+	if f.cpu.IsFree(register) {
+		return
+	}
+
+	var variable *Variable
+
+	for _, v := range f.variables {
+		if v.Register == register {
+			variable = v
+			break
+		}
+	}
+
+	if variable == nil || variable.UsesRemaining == 0 {
+		return
+	}
+
+	newRegister, exists := f.cpu.FindFree(f.cpu.General)
+
+	if !exists {
+		panic("no free registers")
+	}
+
+	f.assembler.RegisterRegister(asm.MOVE, newRegister, register)
+	f.cpu.Free(register)
+	f.cpu.Use(newRegister)
+	variable.Register = newRegister
+}