[LLVMbugs] [Bug 12607] New: llvm-link behavior change (3.1 vs 2.9) with GlobalAliases

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12607

             Bug #: 12607
           Summary: llvm-link behavior change (3.1 vs 2.9) with
                    GlobalAliases
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: boulos at cs.stanford.edu
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


I've got some bitcode I produce with clang and then link with llvm-link before
loading at runtime for use in a JIT.  We're currently using LLVM 2.9, and in
preparing for a change to LLVM 3.1 I ran into a "recursively calling the JIT"
assert.  I tracked it down to being a difference in my linked module: in LLVM
2.9 aliases seem to be resolved at link time (calls to an alias are replaced by
calls to the underlying function), while in 3.1 the calls to the alias remain.

Here's the simplest IR I could make that demonstrates the problem (including
the result of llvm-link AliasDefn.ll AliasUse.ll with both LLVM 2.9 and 3.1):

-------------------------
; AliasDefn.ll
@MyAlias = alias void ()* @Aliasee

define void @Aliasee() {
entry:
  ret void
}

-------------------------
; AliasUse.ll
declare void @MyAlias()

define void @Caller() {
entry:
  call void @MyAlias()
  ret void
}

-------------------------
; ModuleID = 'Alias29.bc'
@MyAlias = alias void ()* @Aliasee

define void @Aliasee() {
entry:
  ret void
}

define void @Caller() {
entry:
  call void @Aliasee()
  ret void
}

-------------------------
; ModuleID = 'Alias31.bc'

@MyAlias = alias void ()* @Aliasee

define void @Aliasee() {
entry:
  ret void
}

define void @Caller() {
entry:
  call void @MyAlias()
  ret void
}


-------------------------

Is this behavior expected?  Should I be complaining about the behavior in
JITEmitter::getPointerToGlobal instead?

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