From 593bb7d44082872e56b762fed374ad414245f4c2 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Sun, 30 Jun 2024 08:59:50 +0200
Subject: Add while loop compilation

---
 src/compiler.c        | 34 ++++++++++++++++++++++++++++++++++
 tests/compilation.bad |  6 ++----
 tests/fib.bad         | 12 ++++++++++++
 3 files changed, 48 insertions(+), 4 deletions(-)
 create mode 100644 tests/fib.bad

diff --git a/src/compiler.c b/src/compiler.c
index 0f9607e..ea9234a 100644
--- a/src/compiler.c
+++ b/src/compiler.c
@@ -558,9 +558,43 @@ compile_if(Chunk *chunk, Node *node) {
     return (CompResult){.type = COMP_NIL};
 }
 
+CompResult
+compile_while(Chunk *chunk, Node *node) {
+    sz start = array_size(chunk->code);
+    CompResult cond = compile_expr(chunk, node->while_cond);
+    OpCode jmpop;
+    switch (cond.type) {
+        case COMP_CONST: {
+            jmpop = OP_JMPFI;
+        } break;
+        case COMP_REG: {
+            jmpop = OP_JMPF;
+        } break;
+        default: {
+            return (CompResult){.type = COMP_ERR};
+        } break;
+    }
+    sz jump_a = array_size(chunk->code);
+
+    // Jump to the `end of the loop` branch.
+    EMIT_OP(jmpop, cond.idx, 0xff, 0, node->while_cond, chunk);
+
+    // Condition is true.
+    CompResult then_expr = compile_expr(chunk, node->while_expr);
+    sz end_expr = array_size(chunk->code);
+    sz loopback = add_constant(chunk, (start - end_expr));
+    EMIT_OP(OP_JMPI, loopback, 0, 0, node, chunk);
+    sz const_a = add_constant(chunk, end_expr - jump_a + 1);
+    chunk->code[jump_a].a = const_a;
+
+    // Return.
+    return (CompResult){.type = COMP_NIL};
+}
+
 CompResult
 compile_expr(Chunk *chunk, Node *node) {
     switch (node->kind) {
+        case NODE_WHILE: return compile_while(chunk, node);
         case NODE_IF: return compile_if(chunk, node);
         // Logic.
         // case NODE_XOR:
diff --git a/tests/compilation.bad b/tests/compilation.bad
index afb2be0..187d4ae 100644
--- a/tests/compilation.bad
+++ b/tests/compilation.bad
@@ -18,10 +18,8 @@
 ; }
 
 let a = 0
-if 1 != 1 {
-    set a = 1
-} else {
-    set a = 2
+while a < 10 {
+    set a = a + 1
 }
 
 a
diff --git a/tests/fib.bad b/tests/fib.bad
new file mode 100644
index 0000000..8eec0b8
--- /dev/null
+++ b/tests/fib.bad
@@ -0,0 +1,12 @@
+let n = 90
+let a = 0
+let b = 1
+let i = 0
+while i < n {
+    let tmp = a + b
+    set a = b
+    set b = tmp
+    set i = i + 1
+}
+
+a
-- 
cgit v1.2.1