C compiler - parse example walkthrough

Abstract syntax tree generation example

"5+20-4;"

  .globl main
main: 
 mov $4, %rax
 push %rax
 mov $20, %rax
 push %rax
 mov $5, %rax
 pop %rdi
 add %rdi, %rax
 pop %rdi
 sub %rdi, %rax
  ret

The parse tree looks like this

static void gen_expr(Node* node) {
  switch(node->kind) {
    case ND_NUM:
    printf(" mov $%d, %%rax\n", node->val);
    return;

    case ND_NEG:
    gen_expr(node->lhs);
    printf(" neg %%rax\n");
    return;
  }

  gen_expr(node->rhs);
  push();
  gen_expr(node->lhs);
  pop("%rdi");

  switch(node->kind) {
    case ND_ADD:
    printf(" add %%rdi, %%rax\n");
    return;
    
    case ND_SUB:
    printf(" sub %%rdi, %%rax\n");
    return;

Abstract syntax tree generation example

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