[WebAssembly][Clang] `_externref_t` usage in global scope emits fatal error in backend

[Losy001]

When targeting WASM, __externref_t emits a fatal error in the backend whenever it's used in global scope.

This error is reproduced here

[llvmbot]

@llvm/issue-subscribers-backend-webassembly

Author: None (Losy001)

When targeting WASM, `__externref_t` emits a fatal error in the backend whenever it's used in global scope.

This error is reproduced here

[woruyu]

This error is similar to #140933, the DAG like this, here I modify def externref : ValueType<32, 195>; in ValueTypes.td file , size to 32, or you will get a align assert error in dump DAG.

SelectionDAG has 8 nodes:
    t0: ch,glue = EntryToken
    t3: i32 = WebAssemblyISD::Wrapper TargetGlobalAddress:i32<ptr @_Z34function_that_gives_me_a_js_objectv> 0
  t4: externref,ch = WebAssemblyISD::CALL t0, t3
    t10: i32 = WebAssemblyISD::Wrapper TargetGlobalAddress:i32<ptr @a> 0
  t8: ch = store<(store (s32) into @a, align 1)> t4:1, t4, t10, undef:i32

The root cause is that due to the lowering of call, some unique types defined by webassembly are introduced, such as funcref and externref，but load and store don't know how to deal with it

[woruyu]

LLVM ir

; ModuleID = 'test.cpp'
source_filename = "test.cpp"
target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-S128-ni:1:10:20"
target triple = "wasm32"

@a = hidden global ptr addrspace(10) null, align 1

; Function Attrs: mustprogress noinline optnone
define hidden void @_Z5entryv() #0 {
  %1 = call ptr addrspace(10) @_Z34function_that_gives_me_a_js_objectv()
  store ptr addrspace(10) %1, ptr @a, align 1
  ret void
}

declare ptr addrspace(10) @_Z34function_that_gives_me_a_js_objectv() #1

attributes #0 = { mustprogress noinline optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+multivalue,+mutable-globals,+nontrapping-fptoint,+reference-types,+sign-ext" }
attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+multivalue,+mutable-globals,+nontrapping-fptoint,+reference-types,+sign-ext" }

!llvm.module.flags = !{!0}
!llvm.ident = !{!1}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{!"Ubuntu clang version 20.1.2 (++20250401083310+e7406753caf3-1~exp1~20250401203329.93)"}