[llvm-dev] Use of array type in globals in LTO

Mehdi Amini via llvm-dev llvm-dev at lists.llvm.org
Fri Aug 26 09:47:08 PDT 2016

> On Aug 26, 2016, at 9:06 AM, junbuml at codeaurora.org wrote:
> On 2016-08-26 11:32, Mehdi Amini wrote:
>> Hi,
>>> Recently, I noticed that less number of global variables are merged in global-merge pass and in some global variable, array types are used instead of its original type. For example, [4xi8] with align 4 is used for a i32  global variable. For me, it seems that such pattern is observed after r278338  (Resolution-based LTO API).
>> Are you sure it is performed in the global merge pass? Can you provide
>> an example of input IR where you see this now but didn’t before?
>> Also can you confirm you’re using the gold-linker?
> I used gold linker. In spec2006/perlbench, I observed the less number of globals are merged in GlobalMerge.cpp after r278338. The reason is because, from the very first pass, several global variables use [4xi8] with align 4, instead of its original type i32 after r278338. Current GlobalMerge pass doesn't seem to handle such fancy-aligned globals. If such type change (e.g., from i32 to [4xi8]) in global variables was intended in r278338, I think we should enhance GlobalMerge to handle such cases.

Can you submit a reproduction for Gold please?
We need to understand what changed with the new LTO API.


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