[llvm-commits] [llvm] r77259 - in /llvm/trunk: docs/LangRef.html include/llvm/Bitcode/LLVMBitCodes.h include/llvm/Operator.h lib/AsmParser/LLLexer.cpp lib/AsmParser/LLParser.cpp lib/AsmParser/LLToken.h lib/Bitcode/Reader/BitcodeReader.cpp lib/Bit

[Török Edwin]

On 2009-07-29 21:11, Eli Friedman wrote:
> 2009/7/29 Török Edwin <edwintorok at gmail.com>:
>   
>> Some optimization (I think LICM) moves getelementptr out of the
>> basicblock where a predicate guarantees the inbounds property, thus you
>> may get
>> a getelementptr that computes an out of bounds value, but when the value
>> is dereferenced it will always be in bounds (due to that predicate).
>>     
>
> That's fine; an invalid getelementptr has an undefined result, but
> it's not undefined behavior by itself.  It's sort of like an undefined
> shift.
>
>   

What happens when you load from it?
Previously the code had no undefined result/undefined behaviour, if LICM
moves it out of the BB
you'll load from an undefined address. Or am I missing something?

Best regards,
--Edwin