llvm dev - Oct 2014 - [LLVMdev] on type annotations of LLVM IR

Hi,

Thank you David.
My question was from a machine independent code analyzer/optimizer
perspective where types are of less importance. Hence I felt difficult to
understand the IR with the types.

Rekha

On Mon, Oct 27, 2014 at 6:44 PM, David Chisnall <David.Chisnall at
cl.cam.ac.uk
> wrote:
> On 27 Oct 2014, at 12:46, Rekha R <rekharamapai at nitc.ac.in> wrote:
>
> > Why wasn't the C style of explicit declaration of variables (or
values
> in LLVM context) followed by their uses model not adopted here?
>
> For the simple reason that there are no variables in LLVM IR.  The SSA
> form means that every value is declared and initialised exactly once.  Some
> values, such as constant integers, are created (in the text serialisation)
> inline in their use so there is no point where they are declared.
>
> > or may be even annotate the value (result of the Instruction) with
type
> rather than annotating each operands on the Instruction?
> >
> > Just felt that by annotating each operand with types may make the
> Instruction 'complex' to understand. May be I am wrong.
>
> You will find it much easier to read when you are debugging.  The IR is
> not intended to be read or written by humans, the text serialisation is
> there as a debugging aid when something has gone wrong.  It is *very*
> useful to be able to look at a single instruction and see all of the types,
> without having to chase through a load of other parts of the code to find
> where things were declared.
>
> David
>
>

-- 
Rekha
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On 27 Oct 2014, at 17:40, Rekha R <rekharamapai at nitc.ac.in> wrote:
> My question was from a machine independent code analyzer/optimizer
perspective where types are of less importance. Hence I felt difficult to
understand the IR with the types.
I'm not sure why you think that types are of less importance there -
that's where they're most used.  When you get to the back end, a lot of
the type information is throw away, as back ends have a far more restricted set
of legal types.

David

Hi,

Currently i am doing an analysis which uses type info in conversion
instructions only. Hence the question.

Rekha

On Mon, Oct 27, 2014 at 11:15 PM, David Chisnall <
David.Chisnall at cl.cam.ac.uk> wrote:
> On 27 Oct 2014, at 17:40, Rekha R <rekharamapai at nitc.ac.in> wrote:
>
> > My question was from a machine independent code analyzer/optimizer
> perspective where types are of less importance. Hence I felt difficult to
> understand the IR with the types.
>
> I'm not sure why you think that types are of less importance there -
> that's where they're most used.  When you get to the back end, a
lot of the
> type information is throw away, as back ends have a far more restricted set
> of legal types.
>
> David
>
>

-- 
Rekha
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