[llvm-dev] why do undefined globals end up in .data instead of .bss? (original) (raw)

Andrew Kelley via llvm-dev llvm-dev at lists.llvm.org
Mon Apr 24 11:55:05 PDT 2017

On Mon, Apr 24, 2017 at 2:53 PM, Friedman, Eli <efriedma at codeaurora.org> wrote:

On 4/23/2017 10:10 AM, Andrew Kelley via llvm-dev wrote:

Here is a module:

@vals = internal unnamedaddr global [20000000 x i32] undef, align 4 LLVM puts the global in the .data section, and results in a 77MB .o file of mostly zeroes. Why does this variable not go in the .bss section?

I think it's just an oversight; it doesn't matter for clang because it never emits globals like that. See TargetLoweringObjectFile::getKindForGlobal for the relevant logic.

I see, thanks. Would a patch be welcome which changed this behavior? Or I suppose I could emit zeroinitializer instead of undef. But it seems like undef is the more correct value. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170424/e64f3701/attachment.html>

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