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