From 8d8a5f973314cb692d543773db8d59a9001b91ad Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Mon, 27 Jun 2022 16:02:41 -0700
Subject: [PATCH] LLVM: support calls to varargs functions

closes #11944
---
 src/codegen/llvm.zig | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index bf09ec0f35..29e25f1079 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -4197,7 +4197,7 @@ pub const FuncGen = struct {
         }
 
         var it = iterateParamTypes(self.dg, fn_info);
-        while (it.next()) |lowering| switch (lowering) {
+        while (it.nextCall(self, args)) |lowering| switch (lowering) {
             .no_bits => continue,
             .byval => {
                 const arg = args[it.zig_index - 1];
@@ -9004,10 +9004,26 @@ const ParamTypeIterator = struct {
         slice,
     };
 
-    fn next(it: *ParamTypeIterator) ?Lowering {
+    pub fn next(it: *ParamTypeIterator) ?Lowering {
         if (it.zig_index >= it.fn_info.param_types.len) return null;
-
         const ty = it.fn_info.param_types[it.zig_index];
+        return nextInner(it, ty);
+    }
+
+    /// `airCall` uses this instead of `next` so that it can take into account variadic functions.
+    pub fn nextCall(it: *ParamTypeIterator, fg: *FuncGen, args: []const Air.Inst.Ref) ?Lowering {
+        if (it.zig_index >= it.fn_info.param_types.len) {
+            if (it.zig_index >= args.len) {
+                return null;
+            } else {
+                return nextInner(it, fg.air.typeOf(args[it.zig_index]));
+            }
+        } else {
+            return nextInner(it, it.fn_info.param_types[it.zig_index]);
+        }
+    }
+
+    fn nextInner(it: *ParamTypeIterator, ty: Type) ?Lowering {
         if (!ty.hasRuntimeBitsIgnoreComptime()) {
             it.zig_index += 1;
             return .no_bits;