llvm dev - Sep 2015 - Rewriting LLVM IR intrinsic functions

Hello,

I can see the occurrences of several LLVM intrinsic functions in the LLVM
IR generated by llvm-dis disassembler. Is there any means to rewrite these
functions reliably using basic LLVM IR statements?


-- 

Thanks & Regards,
Dipanjan
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On Thu, Sep 10, 2015 at 04:20:01PM +0800, Dipanjan Das via llvm-dev
wrote:
> Hello,
> 
> I can see the occurrences of several LLVM intrinsic functions in the LLVM
> IR generated by llvm-dis disassembler. Is there any means to rewrite these
> functions reliably using basic LLVM IR statements?
You can use `LowerIntrinsicCall` from
"llvm/CodeGen/IntrinsicLowering.h"
to do so.

It doesn't seem to be designed to be called from a pass, but with a few
checks it does the job right.

On 10 Sep 2015, at 10:09, serge guelton via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> On Thu, Sep 10, 2015 at 04:20:01PM +0800, Dipanjan Das via llvm-dev wrote:
>> Hello,
>> 
>> I can see the occurrences of several LLVM intrinsic functions in the
LLVM
>> IR generated by llvm-dis disassembler. Is there any means to rewrite
these
>> functions reliably using basic LLVM IR statements?
> 
> You can use `LowerIntrinsicCall` from
"llvm/CodeGen/IntrinsicLowering.h"
> to do so.
This will lower intrinsics to (target-specific) function calls that implement
the underlying functionality, which is almost certainly not what you want to do.

The question doesn’t really make sense.  Intrinsics *are* ‘basic LLVM IR
statements’.  The distinction between things that are intrinsics and things that
are instructions is quite fuzzy.  Many intrinsics are intended to be operations
that map to a single instruction on (at least some) targets and are all things
that are not (or, at least, not easily) representable with LLVM IR instructions.

To answer your question properly, it would help to understand what you’re
actually trying to do.

David