[PATCH] Fix unresolved linker symbols from misplaced extern definitions

[David Majnemer via llvm-commits]

On Tue, Sep 20, 2016 at 3:55 PM, David Majnemer <david.majnemer at gmail.com>
wrote:

>
>
> On Fri, Sep 16, 2016 at 8:15 AM, Chuck Atkins via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> ping?
>>
>> Anybody mind taking a look at this patch?  It's fairly trivial; but
>> without it, builds with the Intel compiler fail.
>>
>
> What is the failure mode?
>


Out of curiosity, does the following make ICC any happier:

diff --git a/lib/Transforms/Utils/LoopUtils.cpp
b/lib/Transforms/Utils/LoopUtils.cpp
index 8878689..1b2a2d6 100644
--- a/lib/Transforms/Utils/LoopUtils.cpp
+++ b/lib/Transforms/Utils/LoopUtils.cpp
@@ -929,6 +929,13 @@ SmallVector<Instruction *, 8>
llvm::findDefsUsedOutsideOfLoop(Loop *L) {
   return UsedOutside;
 }

+// We locally access their IDs here because users shouldn't directly get
them
+// from this header.
+namespace llvm {
+extern char &LoopSimplifyID;
+extern char &LCSSAID;
+}
+
 void llvm::getLoopAnalysisUsage(AnalysisUsage &AU) {
   // By definition, all loop passes need the LoopInfo analysis and the
   // Dominator tree it depends on. Because they all participate in the loop
@@ -938,10 +945,7 @@ void llvm::getLoopAnalysisUsage(AnalysisUsage &AU) {
   AU.addRequired<LoopInfoWrapperPass>();
   AU.addPreserved<LoopInfoWrapperPass>();

-  // We must also preserve LoopSimplify and LCSSA. We locally access their
IDs
-  // here because users shouldn't directly get them from this header.
-  extern char &LoopSimplifyID;
-  extern char &LCSSAID;
+  // We must also preserve LoopSimplify and LCSSA.
   AU.addRequiredID(LoopSimplifyID);
   AU.addPreservedID(LoopSimplifyID);
   AU.addRequiredID(LCSSAID);



>
>
>>
>> On Tue, Sep 13, 2016 at 11:38 AM, Chuck Atkins <chuck.atkins at kitware.com>
>> wrote:
>>
>>> When LCSSAID and LoopSimplifyID are declared extern inside a function
>>> body,
>>> some linkers will fail to resolve the actual symbols defined in the llvm
>>> namespace.  By removing the function local extern declarations and
>>> relying
>>> on the header definitions in Scalar.h, the symbols can be properly
>>> reolved.
>>> This is specifically an issue when building with the Intel compiler.
>>> ---
>>>  lib/Transforms/Utils/LoopUtils.cpp | 3 +--
>>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/lib/Transforms/Utils/LoopUtils.cpp
>>> b/lib/Transforms/Utils/LoopUtils.cpp
>>> index 3902c67..9a1cd0b 100644
>>> --- a/lib/Transforms/Utils/LoopUtils.cpp
>>> +++ b/lib/Transforms/Utils/LoopUtils.cpp
>>> @@ -26,6 +26,7 @@
>>>  #include "llvm/IR/ValueHandle.h"
>>>  #include "llvm/Pass.h"
>>>  #include "llvm/Support/Debug.h"
>>> +#include "llvm/Transforms/Scalar.h"
>>>  #include "llvm/Transforms/Utils/LoopUtils.h"
>>>
>>>  using namespace llvm;
>>> @@ -845,8 +846,6 @@ void llvm::getLoopAnalysisUsage(AnalysisUsage &AU) {
>>>
>>>    // We must also preserve LoopSimplify and LCSSA. We locally access
>>> their IDs
>>>    // here because users shouldn't directly get them from this header.
>>> -  extern char &LoopSimplifyID;
>>> -  extern char &LCSSAID;
>>>    AU.addRequiredID(LoopSimplifyID);
>>>    AU.addPreservedID(LoopSimplifyID);
>>>    AU.addRequiredID(LCSSAID);
>>> --
>>> 2.7.4
>>>
>>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160920/e6e33731/attachment.html>