llvm dev - Oct 2006 - [LLVMdev] How to insert two instructions with the same name?

Hi,

i want to insert a PHI into one basicblock like this:

%s.1 = phi int [ 80, %entry ], [ %tmp21, %bb17 ]

then, insert a cast inst. into another basicblock like this:

%s.1 = cast int %s.1 to uint

But, when i do this, the llvm automatically change the same name into a new
one.

Actually, i found that sometimes, llvm will create bytecode containing two
instructions with same name. So, how can i implement that?

Thanks,
Sheng.
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On Oct 8, 2006, at 1:15 AM, Zhou Sheng wrote:
> i want to insert a PHI into one basicblock like this:
>
> %s.1 = phi int [ 80, %entry ], [ %tmp21, %bb17 ]
>
> then, insert a cast inst. into another basicblock like this:
>
> %s.1 = cast int %s.1 to uint
>
> But, when i do this, the llvm automatically change the same name  
> into a new one.
>
In SSA, any assignment creates a new variable. So it'd probably be  
called something like "%s.2" or whatever. Technically, LLVM
doesn't
care what the names of these variables are. They aren't used in the  
internal representation. Only pointers to instructions matter (and  
they're unique).
> Actually, i found that sometimes, llvm will create bytecode  
> containing two instructions with same name. So, how can i implement  
> that?
>
Again, the names are meaningless and are given only because the user  
needs to be able to understand the .ll code. So it's entirely  
possible to have multiple variables with the same name.

-bw

Just to be clear ...

On Sun, 2006-10-08 at 01:37 -0700, Bill Wendling wrote:
> On Oct 8, 2006, at 1:15 AM, Zhou Sheng wrote:
> > Actually, i found that sometimes, llvm will create bytecode  
> > containing two instructions with same name. So, how can i implement  
> > that?
> >
> Again, the names are meaningless and are given only because the user  
> needs to be able to understand the .ll code. So it's entirely  
> possible to have multiple variables with the same name.
The same variable name can only appear across "type planes". That is,
there cannot be two identical names that refer to the same type.
However, the same name can be used to refer to different types.  To
assist in this, the LLVM SymbolTable will automatically append an
monotonically increasing integer value to the name of any duplicate.
For example:

void %func() { 
  %s = cast int 1 to int
  %s = cast long 1 to long
  %a = cast int 2 to int
  %a = cast long 2 to long
ret void 
}

is completely legal. The %s and %a names don't conflict because they
have different types (int and long).

Reid.