[LLVMdev] [RFC] Extend LLVM IR to express "fast-math" at a per-instruction level

[Chris Lattner]

On Nov 14, 2012, at 5:23 PM, Michael Ilseman <milseman at apple.com> wrote:
>> Ah I see.  So this just becomes a matter of interpretation of bits in the optimization flags.  Shouldn't need to promote the CurVersion.
>> 
>> Nitpick: 80-cols in BitcodeReader.cpp
>> 
>> Since Instruction::FastMathFlags is a class, seems like the constructor could take in Record[OpNum] , and assign the flags.
>> 
> 
> I like the intent, but unfortunately Record[OpNum] is just a uint64_t. The agreement of which bit means what is in LLVMBitCodes.h, and I'd prefer not having an implicit handshake between the bitcode and the rest of LLVM. However, I'll try to find ways to factor more convenience into shared code.

It's also a current design policy to explicitly enumerate the bitcode code separately from internal codes.  This is because there should be no binary compatibility concerns with renumbering internal IR enums, but if bitcode uses them directly, we'd have a problem.

-Chris