From 3fe55b5e51e698d0fcf8bad8c23f876f690fe367 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Tue, 20 Jan 2026 16:46:47 +0100
Subject: [PATCH] - Vectors not converted to arrays when passed as raw vaargs.
 #2776

---
 releasenotes.md                               |  3 +-
 src/compiler/sema_casts.c                     |  6 +++
 test/test_suite/abi/sysv_abi_vaarg_vector.c3t | 39 +++++++++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 test/test_suite/abi/sysv_abi_vaarg_vector.c3t

diff --git a/releasenotes.md b/releasenotes.md
index 6565a8a1f..5c4b880cd 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -20,7 +20,8 @@
 - Module-based generics using {} is deprecated.
 - Create optional with `~` instead of `?`. `return io::EOF?;` becomes `return io::EOF~`.
 - Deprecated use of `?` to create optional.
- 
+- Vectors not converted to arrays when passed as raw vaargs. #2776
+
 ### Fixes
 - Regression with npot vector in struct triggering an assert #2219.
 - Casting bitstruct to wider base type should be single step #2616.
diff --git a/src/compiler/sema_casts.c b/src/compiler/sema_casts.c
index 024148995..99b1488a1 100644
--- a/src/compiler/sema_casts.c
+++ b/src/compiler/sema_casts.c
@@ -259,6 +259,12 @@ void cast_promote_vararg(Expr *arg)
 		cast_no_check(arg, type_get_ptr(arg_type->array.base), IS_OPTIONAL(arg));
 	}
 
+	// We convert non-simd vectors to arrays
+	if (arg_type->type_kind == TYPE_VECTOR)
+	{
+		cast_no_check(arg, type_array_from_vector(arg_type), IS_OPTIONAL(arg));
+	}
+
 }
 
 /**
diff --git a/test/test_suite/abi/sysv_abi_vaarg_vector.c3t b/test/test_suite/abi/sysv_abi_vaarg_vector.c3t
new file mode 100644
index 000000000..46ac2643f
--- /dev/null
+++ b/test/test_suite/abi/sysv_abi_vaarg_vector.c3t
@@ -0,0 +1,39 @@
+// #target: linux-x64
+// #opt: --x86cpu=avx512
+module test;
+import libc;
+fn void testi()
+{
+	int[<4>] y = { 1, 2, 3, 4 };
+	libc::printf("", y[0], y );
+}
+fn void main()
+{
+	testi();
+}
+
+/* #expect: test.ll
+
+define void @test.testi() #0 {
+entry:
+  %y = alloca <4 x i32>, align 16
+  %taddr = alloca [4 x i32], align 16
+  store <4 x i32> <i32 1, i32 2, i32 3, i32 4>, ptr %y, align 16
+  %0 = load <4 x i32>, ptr %y, align 16
+  %1 = extractelement <4 x i32> %0, i64 0
+  %2 = load <4 x i32>, ptr %y, align 16
+  %3 = extractelement <4 x i32> %2, i64 0
+  %4 = insertvalue [4 x i32] undef, i32 %3, 0
+  %5 = extractelement <4 x i32> %2, i64 1
+  %6 = insertvalue [4 x i32] %4, i32 %5, 1
+  %7 = extractelement <4 x i32> %2, i64 2
+  %8 = insertvalue [4 x i32] %6, i32 %7, 2
+  %9 = extractelement <4 x i32> %2, i64 3
+  %10 = insertvalue [4 x i32] %8, i32 %9, 3
+  store [4 x i32] %10, ptr %taddr, align 16
+  %lo = load i64, ptr %taddr, align 16
+  %ptradd = getelementptr inbounds i8, ptr %taddr, i64 8
+  %hi = load i64, ptr %ptradd, align 8
+  %11 = call i32 (ptr, ...) @printf(ptr @.str, i32 %1, i64 %lo, i64 %hi)
+  ret void
+}