Implemented compilation to SSA form

src/ssa/Block.go

@@ -2,11 +2,11 @@ package ssa
 
 // Block is a list of instructions that can be targeted in branches.
 type Block struct {
-	Instructions []Instruction
+	Instructions []Value
 }
 
 // Append adds a new instruction to the block.
-func (b *Block) Append(instr Instruction) *Instruction {
+func (b *Block) Append(instr Value) *Value {
 	b.Instructions = append(b.Instructions, instr)
 	return &b.Instructions[len(b.Instructions)-1]
 }