[llvm-bugs] [Bug 40364] New: Handling of extern globals in WebAssembly

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40364

            Bug ID: 40364
           Summary: Handling of extern globals in WebAssembly
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: All Bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: alonzakai at gmail.com
                CC: llvm-bugs at lists.llvm.org, peter.smith at linaro.org

They seem to be turned into address 0:

extern "C" int foo;
int main() {
  foo++;
  return foo;
}

==>  emcc a.cpp -o a.bc  ==>

@foo = external global i32, align 4

; Function Attrs: noinline norecurse nounwind optnone
define hidden i32 @main() #0 {
entry:
  %retval = alloca i32, align 4
  store i32 0, i32* %retval, align 4
  %0 = load i32, i32* @foo, align 4
  %inc = add nsw i32 %0, 1
  store i32 %inc, i32* @foo, align 4
  %1 = load i32, i32* @foo, align 4
  ret i32 %1
}

==>  wasm-ld a.bc -o a.wasm --entry=main --no-gc-sections --export-dynamic  ==>

 (func $main (; 1 ;) (type $1) (result i32)
  [..]
  (i32.store
   (i32.const 0)
   (i32.add
    (i32.load
     (i32.const 0)
    )
    (i32.const 1)
   )
  )
  (i32.load
   (i32.const 0)
  )
 )

Perhaps they should be handled like extern functions, that is, an import would
be emitted, something like

 (import "env" "foo" (global $gimport$0 i32))

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