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  • Chris Lattner's avatar
    Land the long talked about "type system rewrite" patch. This · b1ed91f3
    Chris Lattner authored
    patch brings numerous advantages to LLVM.  One way to look at it
    is through diffstat:
     109 files changed, 3005 insertions(+), 5906 deletions(-)
    
    Removing almost 3K lines of code is a good thing.  Other advantages
    include:
    
    1. Value::getType() is a simple load that can be CSE'd, not a mutating
       union-find operation.
    2. Types a uniqued and never move once created, defining away PATypeHolder.
    3. Structs can be "named" now, and their name is part of the identity that
       uniques them.  This means that the compiler doesn't merge them structurally
       which makes the IR much less confusing.
    4. Now that there is no way to get a cycle in a type graph without a named
       struct type, "upreferences" go away.
    5. Type refinement is completely gone, which should make LTO much MUCH faster
       in some common cases with C++ code.
    6. Types are now generally immutable, so we can use "Type *" instead 
       "const Type *" everywhere.
    
    Downsides of this patch are that it removes some functions from the C API,
    so people using those will have to upgrade to (not yet added) new API.  
    "LLVM 3.0" is the right time to do this.
    
    There are still some cleanups pending after this, this patch is large enough
    as-is.
    
    llvm-svn: 134829
    b1ed91f3
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