From 38942c34a497a4c6edf080dc64440c1bc486fc46 Mon Sep 17 00:00:00 2001
From: Elis Eriksson <spelis@spelis.li>
Date: Sat, 20 Jun 2026 20:12:29 +0200
Subject: Pattern matching optimizer and more

it's not the best optimizer but it works.
Also added a -ast_dump flag which dumps the AST to stderr.
Also input is now done in raw mode just because it can be.
---
 src/optimizer.c | 134 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 src/optimizer.c

(limited to 'src/optimizer.c')

diff --git a/src/optimizer.c b/src/optimizer.c
new file mode 100644
index 0000000..18a88c5
--- /dev/null
+++ b/src/optimizer.c
@@ -0,0 +1,134 @@
+#include "all.h"
+#include <stdbool.h>
+#include <stddef.h>
+
+static void mark_changed(bool *ch) { *ch = true; }
+
+static bool is_arith(ast_type_e t) { return t == AST_INC || t == AST_DEC; }
+
+static bool is_ptr(ast_type_e t) {
+  return t == AST_PTR_INC || t == AST_PTR_DEC;
+}
+
+static int node_signed_value(const ast_node_t *n) {
+  if (n->type == AST_DEC || n->type == AST_PTR_DEC)
+    return -n->val;
+  return n->val;
+}
+
+static void set_arith_node(ast_node_t *n, int v) {
+  if (v > 0) {
+    n->type = AST_INC;
+    n->val = v;
+  } else {
+    n->type = AST_DEC;
+    n->val = -v;
+  }
+}
+
+static void set_ptr_node(ast_node_t *n, int v) {
+  if (v > 0) {
+    n->type = AST_PTR_INC;
+    n->val = v;
+  } else {
+    n->type = AST_PTR_DEC;
+    n->val = -v;
+  }
+}
+
+static void optimize_list(ast_node_t **head, bool *ch);
+
+static void optimize_loop_node(ast_node_t *n, bool *ch) {
+  if (!n || n->type != AST_LOOP)
+    return;
+
+  if (n->children.len == 0 || n->children._data[0] == NULL) {
+    n->children.len = 0;
+    return;
+  }
+
+  optimize_list(&n->children._data[0], ch);
+
+  if (n->children._data[0] == NULL) {
+    n->children.len = 0;
+    return;
+  }
+
+  if (n->children.len == 1) {
+    ast_node_t *c = n->children._data[0];
+
+    if ((c->type == AST_INC || c->type == AST_DEC) && c->val == 1) {
+      n->type = AST_CLEAR;
+      n->val = 0;
+      n->children.len = 0;
+      n->children._data[0] = NULL;
+      mark_changed(ch);
+    }
+  }
+}
+
+static void optimize_list(ast_node_t **head, bool *ch) {
+  ast_node_t **p = head;
+
+  while (*p) {
+    ast_node_t *n = *p;
+
+    if (n->type == AST_LOOP) {
+      optimize_loop_node(n, ch);
+
+      if (n->type == AST_LOOP && n->children.len == 0) {
+        *p = n->next;
+        mark_changed(ch);
+        continue;
+      }
+    }
+
+    if (*p && (*p)->next) {
+      ast_node_t *a = *p;
+      ast_node_t *b = a->next;
+
+      if (is_arith(a->type) && is_arith(b->type)) {
+        int v = node_signed_value(a) + node_signed_value(b);
+
+        if (v == 0) {
+          a->next = b->next;
+          mark_changed(ch);
+          continue;
+        }
+
+        set_arith_node(a, v);
+        a->next = b->next;
+        mark_changed(ch);
+        continue;
+      }
+
+      if (is_ptr(a->type) && is_ptr(b->type)) {
+        int v = node_signed_value(a) + node_signed_value(b);
+
+        if (v == 0) {
+          a->next = b->next;
+          mark_changed(ch);
+          continue;
+        }
+
+        set_ptr_node(a, v);
+        a->next = b->next;
+        mark_changed(ch);
+        continue;
+      }
+    }
+
+    p = &(*p)->next;
+  }
+}
+
+ast_node_t *optimize_ast(ast_node_t *ast) {
+  bool ch;
+
+  do {
+    ch = false;
+    optimize_list(&ast, &ch);
+  } while (ch);
+
+  return ast;
+}
-- 
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