[LLVMdev] Stop MachineCSE on certain instructions
evan.cheng at apple.com
Tue Dec 20 13:43:34 PST 2011
If an instruction is marked as side-effect free then it's a candidate for CSE. Try marking the instruction with hasSideEffects.
On Dec 17, 2011, at 12:24 PM, Johannes Birgmeier wrote:
> I'm writing for a backend and have a complicated instruction bundle (3
> instructions) that has to be executed like a single block (meaning: if
> the first instruction is executed, all three have to be executed to
> obtain the result, though not necessarily without other instructions in
> between). Unfortunately, MachineCSE gets in the way sometimes and rips
> it apart.
> Is there a way to stop CSE from doing its thing (common subexpression
> elimination) for certain instructions?
> I've already tried glueing (gluing?) them together, but that doesn't
> seem to make a difference.
> Johannes Birgmeier
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
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