fix: stack offset calculation of local variables of functions having many parameters

`calc_lvar_stack_offset()` previously only checked the offset of the last local variables, but it might be a
passed-by-stack parameter, which had a negative stack offset.

With this change, `calc_lvar_stack_offset()` finds the maximum *positive* offset from local variables.

2 files changed, 18 insertions, 8 deletions

diff --git a/src/parse.c b/src/parse.c
index 308277f..f7fec94 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -237,15 +237,16 @@ static int find_lvar(Parser* p, const char* name) {
 }
 
 static int calc_lvar_stack_offset(Parser* p, Type* ty) {
-    int offset;
-    if (p->lvars.len == 0) {
-        offset = 0;
-    } else {
-        offset = p->lvars.data[p->lvars.len - 1].stack_offset;
-        if (offset < 0)
-            offset = 0;
+    int last_offset = 0;
+    for (int i = p->lvars.len - 1; i >= 0; i--) {
+        int offset = p->lvars.data[i].stack_offset;
+        // Skip a passed-by-stack parameter.
+        if (offset <= 0)
+            continue;
+        last_offset = offset;
+        break;
     }
-    return to_aligned(offset + type_sizeof(ty), type_alignof(ty));
+    return to_aligned(last_offset + type_sizeof(ty), type_alignof(ty));
 }
 
 static int add_lvar(Parser* p, const char* name, Type* ty, int stack_offset) {
diff --git a/tests/functions.c b/tests/functions.c
index 6e4622c..4911d7c 100644
--- a/tests/functions.c
+++ b/tests/functions.c
@@ -100,6 +100,12 @@ int f10() {
     return 12345;
 }
 
+int f11(int* a, int* b, int* c, int* d, int* e, int* f, int* g) {
+    int x = 99;
+    int* local = &x;
+    return *a + *b + *c + *d + *e + *f + *g + *local;
+}
+
 int sum(int n, ...) {
     va_list args;
     va_start(args, n);
@@ -143,6 +149,9 @@ int main() {
     S s;
     s.x = 5;
     s.y = 6;
+    int v1 = 1, v2 = 2, v3 = 3, v4 = 4, v5 = 5, v6 = 6, v7 = 7;
+    ASSERT_EQ(1 + 2 + 3 + 4 + 5 + 6 + 7 + 99, f11(&v1, &v2, &v3, &v4, &v5, &v6, &v7));
+
     ASSERT_EQ(1, f9(0, 1, 2, 3, 4, s, 7, 8));
     ASSERT_EQ(2, f9(1, 1, 2, 3, 4, s, 7, 8));
     ASSERT_EQ(3, f9(2, 1, 2, 3, 4, s, 7, 8));