[llvm-dev] Optimization Barrier in LLVM Backends

[Rob Lyerly via llvm-dev]

Hello,

Is it possible to prevent optimizations across a given machine instruction,
i.e., some sort of "optimization barrier", when doing architecture-specific
optimizations during code generation?  For example, I'd like to be able to
insert some form of instrumentation prevent an optimization pass from
lifting a common sub-expression across a given machine instruction.

I'm interested in capturing and maintaining an equivalent set of live
values across compilations for different architectures, similarly to what
is expressed in "A Unified Model of Pointwise Equivalence of Procedural
Computations" (http://dl.acm.org/citation.cfm?id=197402).
Architecture-specific optimizations very often create architecture-specific
live values, which makes it hard to map live values between different
architectures.

Thanks for any help!

-- 
Rob Lyerly
Graduate Research Assistant, Systems Software Research Group
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