LLVM type error when using vector types with FFI

Summary

When a foreign function has a different vector types for parameter and return types, the LLVM IR emitted by GHC contains type errors.

Steps to reproduce

Consider the following code:

-- Main.hs
{-# LANGUAGE MagicHash, UnboxedTuples, ExtendedLiterals #-}
import GHC.Exts
import GHC.Int
import MyLib

main :: IO ()
main = do
  let a = broadcastInt32X4# 100#Int32
      b = broadcastInt32X4# 200#Int32
      c = packsi32 a b
      (# x0, x1, x2, x3, x4, x5, x6, x7 #) = unpackInt16X8# c
  print (I16# x0, I16# x1, I16# x2, I16# x3, I16# x4, I16# x5, I16# x6, I16# x7)

-- MyLib.hs
{-# LANGUAGE MagicHash, UnliftedFFITypes #-}
module MyLib where
import GHC.Exts

foreign import ccall unsafe
  packsi32 :: Int32X4# -> Int32X4# -> Int16X8#

// packs.c
#include <emmintrin.h>
#include <stdio.h>

__m128i packsi32(__m128i a, __m128i b)
{
    return _mm_packs_epi32(a, b);
}

$ ghc -fforce-recomp -fllvm Main.hs packs.c
[1 of 3] Compiling MyLib            ( MyLib.hs, MyLib.o )
opt-15: /tmp/ghc242850_tmp_0/ghc_tmp_7_0.ll:103:20: error: '%XMM1_Arg' defined with type '<4 x i32>' but expected '<8 x i16>'
  store <8 x i16>  %XMM1_Arg, <8 x i16>*  %XMM1_Var
                   ^
<no location info>: error:
    `opt-15' failed in phase `LLVM Optimiser'. (Exit code: 1)

Expected behavior

The program should compile and output:

$ ./Main
(100,100,100,100,200,200,200,200)

Environment

• GHC version used: 9.12.1, 9.13.20250206 (5622a14a)
• Operating System: Ubuntu 22.04
• System Architecture: x86_64