[LLVMdev] Weak store / Memory hints

[Carl-Philip Hänsch]

Hello LLVM list,

I am writing a JIT compiler for a SQL in-memory database and I have an
issue:
I want to compile specialized functions per-object which replace a virtual
function call.

What I want to achieve is to feed memory from runtime into the code. I know
the runtime value behind some values (especially the 'this' pointer) and
want llvm to profit from that additional knowledge for instance by
replacing loads of memory where I know it's constant (i.e. the virtual
function table; some fields that are only changed in the constructor, etc.)

In the moment I see 3 ways to achieve this
1. find all loads, check the range and replace them by their loaded value
2. add store instructions in the beginning of the code that override the
"unknown" values with their known parts (ugly - consumes memory bandwith
and requires an additional GVN pass)
3. a weak store instruction which is ignored by the code generator but
gives hints to the load-store-optimization
4. do have an other idea?

Greetings
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20131122/8d64080d/attachment.html>