llvm dev - Apr 2010 - [LLVMdev] Unknown or runtime type in function definition?

Hello all,

I'm trying to understand a bit of LLVM IR syntax.  I have a function
definition which looks like this in IR:

    define void @foo(%1* ptr) { ...

The C code for foo has a definition that looks like:

    typedef struct bar_struct bar;
    ... Definition of struct bar_struct ...
    void foo(bar *ptr) { ...

I can't whittle down a convenient test source file just now; but I'm
trying
to understand what the syntax of the 'define' above means --
specifically,
what does it mean for a parameter to have type '%1*'?  What is the
semantics
here?  Inside the body of @foo, there is an SSA variable %1 -- is that
variable related to the %1 in the type of the parameter?  (It doesn't seem
to be, which is why I ask.)

I looked in the LLVM Language Reference manual but couldn't find any type
syntax that corresponded to the type I see for foo's parameter.  I'm not
sure where else to look, but I'd be happy to hear any pointers.

Any help is appreciated.  Thanks in advance.

-Denis

On Fri, Apr 9, 2010 at 2:11 PM, Bueno, Denis <denbuen at sandia.gov>
wrote:
> Hello all,
>
> I'm trying to understand a bit of LLVM IR syntax.  I have a function
> definition which looks like this in IR:
>
>    define void @foo(%1* ptr) { ...
>
> The C code for foo has a definition that looks like:
>
>    typedef struct bar_struct bar;
>    ... Definition of struct bar_struct ...
>    void foo(bar *ptr) { ...
>
> I can't whittle down a convenient test source file just now; but
I'm trying
> to understand what the syntax of the 'define' above means --
specifically,
> what does it mean for a parameter to have type '%1*'?  What is the
semantics
> here?  Inside the body of @foo, there is an SSA variable %1 -- is that
> variable related to the %1 in the type of the parameter?  (It doesn't
seem
> to be, which is why I ask.)
In that context, %1 refers to an unnamed struct; whether %1 refers to
a type or a value is determined by the context.  Short example which
should help:

%0 = type { i32, float, float, double }
define i32 @a(%0*) {
entry:
  getelementptr %0* %0, i32 0, i32 0
  load i32* %1
  ret i32 %2
}

-Eli

On 4/9/10 4:11 PM, "Eli Friedman" <eli.friedman at gmail.com>
wrote:
> In that context, %1 refers to an unnamed struct; whether %1 refers to
> a type or a value is determined by the context.  Short example which
> should help:
> 
> %0 = type { i32, float, float, double }
> define i32 @a(%0*) {
> entry:
>   getelementptr %0* %0, i32 0, i32 0
>   load i32* %1
>   ret i32 %2
> }
Okay.  Looking back over the IR, I see a type %1 defined at the top of the
module.  Thanks!

-Denis

On Fri, Apr 9, 2010 at 3:11 PM, Eli Friedman <eli.friedman at gmail.com>
wrote:
> On Fri, Apr 9, 2010 at 2:11 PM, Bueno, Denis <denbuen at sandia.gov>
wrote:
>> Hello all,
>>
>> I'm trying to understand a bit of LLVM IR syntax.  I have a
function
>> definition which looks like this in IR:
>>
>>    define void @foo(%1* ptr) { ...
>>
>> The C code for foo has a definition that looks like:
>>
>>    typedef struct bar_struct bar;
>>    ... Definition of struct bar_struct ...
>>    void foo(bar *ptr) { ...
>>
>> I can't whittle down a convenient test source file just now; but
I'm trying
>> to understand what the syntax of the 'define' above means --
specifically,
>> what does it mean for a parameter to have type '%1*'?  What is
the semantics
>> here?  Inside the body of @foo, there is an SSA variable %1 -- is that
>> variable related to the %1 in the type of the parameter?  (It
doesn't seem
>> to be, which is why I ask.)
>
> In that context, %1 refers to an unnamed struct; whether %1 refers to
> a type or a value is determined by the context.  Short example which
> should help:
FWIW, I personally regard this as a bug not a feature. It doesn't make
the IR any easier to read.

 - Daniel
>
> %0 = type { i32, float, float, double }
> define i32 @a(%0*) {
> entry:
>  getelementptr %0* %0, i32 0, i32 0
>  load i32* %1
>  ret i32 %2
> }
>
> -Eli
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>