llvm dev - Nov 2003 - [LLVMdev] Question about structure of SymbolTable

I was trying to look through the SymbolTable code for LLVM.  What does 
the SymbolTable for a Module contain?  Is it just GlobalVariables and 
Functions?  How are program constants and static variables declared 
within functions handled?  When I said program constants, I meant 
things like strings (e.g., char* foo = "Hello world\n";).  Thanks in 
advance.

Sincerely,
Brian


Brian M. Fahs
Graduate Student
University of Illinois

On Mon, 17 Nov 2003, Brian Fahs wrote:
> I was trying to look through the SymbolTable code for LLVM.  What does
> the SymbolTable for a Module contain?  Is it just GlobalVariables and
> Functions?
The Module-level symbol table contains types, global variables and
functions.
> How are program constants and static variables declared within functions
> handled?  When I said program constants, I meant things like strings
> (e.g., char* foo = "Hello world\n";).
You can try it out on the demo page:
http://llvm.cs.uiuc.edu/demo/

... but the answer to your question is that the C front-end transforms
them into global variables.  Thus, the constant string "Hello world\n"
turns into the LLVM global:

%.str_1 = internal constant [13 x sbyte] c"Hello world\0A\00"

File static variables are handled similarly,

-Chris

-- 
http://llvm.cs.uiuc.edu/
http://www.nondot.org/~sabre/Projects/

Brian,

Global symbols including new named types are named in the global symbol 
table.  In addition each function contains a local symbol table naming 
local items, including temporary variables.

I'm busy documenting all this, but I'm also busy writing a code
generator
for my architecture, so haven't gotten enough through everything to 
completely document the bytecode language.  Symbol tables in LLVM are easy 
though.

Hope this answers your question.

-- Robert.

At 06:04 PM 11/17/2003 -0600, Brian Fahs wrote:
>I was trying to look through the SymbolTable code for LLVM.  What does the 
>SymbolTable for a Module contain?  Is it just GlobalVariables and 
>Functions?  How are program constants and static variables declared within 
>functions handled?  When I said program constants, I meant things like 
>strings (e.g., char* foo = "Hello world\n";).  Thanks in advance.
>
>Sincerely,
>Brian
>
>
>Brian M. Fahs
>Graduate Student
>University of Illinois
>
>_______________________________________________
>LLVM Developers mailing list
>LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
Robert Mykland     Voice: (831) 462-6725

> Global symbols including new named types are named in the global symbol
> table.  In addition each function contains a local symbol table naming
> local items, including temporary variables.
To further the confusion on this issue, I am planning on making a change
to the LLVM classes (not the bytecode or asm files) w.r.t types and the
symbol table.  Basically, the symbol table class needs to be cleaned up a
bit, and will end up storing types in a separate map from the global
variables and functions (which will still be a part of the SymbolTable
class though).

The end goal of this is to make the Type class not derive from Value: you
can't use Types in any context where a value makes sense anyway.  For more
information on other planned cleanups, see:

http://llvm.cs.uiuc.edu/PR122

Again, this will not affect the .ll or .bc file formats, only code which
grovels through the symbol table looking for types.  Also note that this
might not happen for another couple of weeks...

-Chris

-- 
http://llvm.cs.uiuc.edu/
http://www.nondot.org/~sabre/Projects/