[PATCH] Eliminate memcpy of undefined values

[Nick Lewycky]

Patrick Walton wrote:
> On 2/4/14 7:33 PM, Patrick Walton wrote:
>> Hi everyone,
>>
>> This patch optimizes out memcpy operations that copy undefined data from
>> fresh allocas. Since the data was already undefined, we can simply not
>> do the memcpy and leave the data that was already there in place. SROA
>> frequently creates these memcpys when aggregates that contain padding
>> are copied around, so this eliminates a significant chunk (0.5% or so)
>> of code from Rust binaries.
>
> Here's a new version per Nick Lewycky's feedback.

Looks good, please commit. (Do you have commit access?)

Nick