[LLVMdev] malloc vs malloc

[Chris Lattner]

On Dec 23, 2008, at 9:14 AM, Jon Harrop wrote:
> I discovered that LLVM's malloc only allows a 32-bit size argument,  
> so you
> cannot use it to allocate huge blocks on 64-bit machines. So I  
> considered
> replacing all of my uses of LLVM's malloc instruction with calls to  
> the libc
> malloc function instead. That got me wondering why LLVM even has its  
> own
> malloc intrinsic anyway...
>
> Am I correct in assuming that LLVM's malloc intrinsic exists so that  
> some
> optimization passes can rewrite it, e.g. replacing heap allocation  
> with stack
> allocation when no part of the allocated value escapes scope? So  
> replacing
> all of my uses of LLVM's malloc with libc's malloc might hamper LLVM's
> optimizations and degrade performance?

Hi Jon,

There is no good reason for malloc to be an instruction anymore.  I'd  
be very happy if it got removed.  Even if we keep it, malloc/alloca  
should be extended to optionally take 64-bit sizes.

-Chris