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Re: Enabling SSA for alpha?
- To: Brad Lucier <lucier at math dot purdue dot edu>
- Subject: Re: Enabling SSA for alpha?
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Wed, 15 Mar 2000 11:52:13 -0700
- cc: gcc at gcc dot gnu dot org
- Reply-To: law at cygnus dot com
In message <200003151846.NAA25538@polya.math.purdue.edu>you write:
> > SSA is not suitable for direct code generation -- you translate into SSA,
> > perform a series of transformations (optimizations), then translate back
> > out of SSA.
>
> OK, does this mean that the SSA pass transforms the code into a form that
> the other passes can't deal with?
No it means that there is no way for the *processor* to implement the
SSA form. Read a little about SSA, particularly the PHI expressions that
must be inserted at dominance frontiers. There's no processor in the
world that I'm aware of that implements the semantics of a PHI expression.
Nor do any of GCC's optimizers know about PHI expressions.
jeff