[llvm] [X86] Fix 32-bit immediate assertion and convert into backend error (PR #123872)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,40 @@
+; RUN: not llc < %s -mtriple=i686 2>&1 | FileCheck %s -check-prefix=i686
+; RUN: llc < %s -mtriple=x86_64 | FileCheck %s -check-prefix=x86_64
+
----------------
arsenm wrote:

Can you add the issue name to the test file 

https://github.com/llvm/llvm-project/pull/123872