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40 lines
1.7 KiB
Plaintext
Date: Tue, 13 Feb 2001 13:29:52 -0600 (CST)
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From: Chris Lattner <sabre@nondot.org>
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To: Vikram S. Adve <vadve@cs.uiuc.edu>
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Subject: LLVM Concerns...
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I've updated the documentation to include load store and allocation
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instructions (please take a look and let me know if I'm on the right
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track):
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file:/home/vadve/lattner/llvm/docs/LangRef.html#memoryops
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I have a couple of concerns I would like to bring up:
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1. Reference types
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Right now, I've spec'd out the language to have a pointer type, which
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works fine for lots of stuff... except that Java really has
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references: constrained pointers that cannot be manipulated: added and
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subtracted, moved, etc... Do we want to have a type like this? It
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could be very nice for analysis (pointer always points to the start of
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an object, etc...) and more closely matches Java semantics. The
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pointer type would be kept for C++ like semantics. Through analysis,
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C++ pointers could be promoted to references in the LLVM
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representation.
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2. Our "implicit" memory references in assembly language:
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After thinking about it, this model has two problems:
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A. If you do pointer analysis and realize that two stores are
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independent and can share the same memory source object, there is
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no way to represent this in either the bytecode or assembly.
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B. When parsing assembly/bytecode, we effectively have to do a full
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SSA generation/PHI node insertion pass to build the dependencies
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when we don't want the "pinned" representation. This is not
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cool.
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I'm tempted to make memory references explicit in both the assembly and
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bytecode to get around this... what do you think?
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-Chris
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