[llvm-commits] [llvm] r113329 - in /llvm/trunk: include/llvm/Analysis/AliasAnalysis.h lib/Analysis/AliasAnalysis.cpp lib/Analysis/BasicAliasAnalysis.cpp

[Dan Gohman]

On Sep 8, 2010, at 1:06 PM, Devang Patel wrote:

> 
> On Sep 7, 2010, at 6:32 PM, Dan Gohman wrote:
> 
>> +    /// ReadThenWrite - The instructions are ReadThenWriteSome and the second
>> +    /// instruction writes to exactly the same memory read from by the first.
>> +    ReadThenWrite,
>> +
> 
> ReadThenWriteSome is missing.

We can add it if there's a need for it. That said, ReadThenWrite isn't
especially urgent either, though it does communicates type safety
(as it's sometimes called at this level).

>> +    /// WriteThenWrite - The instructions are WriteThenWriteSome, and the
>> +    /// second instruction writes to exactly the same memory written to by
>> +    /// the first.
>> +    WriteThenWrite,
>> +
>> +    /// WriteSomeThenWrite - Both instructions are write-only, and the second
>> +    /// instruction writes to a superset of the memory written to by the first.
>> +    WriteSomeThenWrite,
> 
> I am curious, why did not you use WriteThenWriteSome alternative ?

These are for DSE. A WriteThenWriteSome would mean that only part
of the first store is potentially dead, which is a lot trickier to handle.
It could be added if someone were interested in that kind of thing.

Dan