[llvm-dev] Aggregate load/stores

Philip Reames via llvm-dev llvm-dev at lists.llvm.org
Mon Aug 17 10:05:23 PDT 2015

On 08/16/2015 10:10 PM, David Majnemer via llvm-dev wrote:
> With the above in mind, I don't see it as unreasonable for frontends 
> to generate IR that LLVM is comfortable with.  We seem fine telling 
> frontend authors that they should strive to avoid large aggregate 
> memory operations in our performance tips guide 
> <http://llvm.org/docs/Frontend/PerformanceTips.html#avoid-loads-and-stores-of-large-aggregate-type>. 
> Implementation experience with Clang hasn't shown this to be 
> particularly odious to follow and none of the LLVM-side solutions seem 
> satisfactory.
David, speaking as the guy who wrote the documentation you're quoting, 
you're twisting the intent of that document.  The document was 
explicitly intended to document current status, warts and all. Please do 
not use it to justify not fixing those warts.  :)

In general, I feel that a solution which worked for FCAs under some 
fixed size (64k, 1MB, fine!) would be better than one that worked for 
none.  We could just document the limitation and call it a day. (I'll 
note that I am not endorsing or discouraging any *particular* solution 
to said problem.)


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