llvm dev - Sep 2006 - [LLVMdev] Bug in WritingAnLLVMPass.html

Hi,

Chris Lattner wrote:
> I'd suggest writing a little pass that strips out debug intrinsics.
>   
OK, I did this and it works (the strange seg fault also disappears after 
all declared debug variables are gone)! In a first phase, all intrinsic 
instructions are discarded after extracting their data into annotations 
attached to the relevant Function. Then, a second phase wipes out the 
intrinsic instruction Functions themselves as well as all debug 
variables in the declaration section. This 2-phase approach is necessary 
as I implemented the pass as an InstVisitor.

A limitation here is that only Functions' debug data can be kept, as 
other Values (i.e. Instructions) are not Annotable. Is this an explicit 
design decision?

Kind regards,

Bram Adams
GH-SEL, INTEC, Ghent University

PS: Could this pass be interesting to others? If so, I could send the 
code to the list or to Bugzilla.

On Tue, 26 Sep 2006, Bram Adams wrote:
>
> A limitation here is that only Functions' debug data can be kept, as
> other Values (i.e. Instructions) are not Annotable. Is this an explicit
> design decision?
Yes, we intentionally do not want things to be annotatable.  In fact, 
Function being annotatable is a wart due to the way the code generator 
currently works.  In general, we prefer to keep data in on-the-side maps 
instead of attached to the IR.  The mailing list has archives of extensive 
discussion about this sort of thing.

-Chris

-- 
http://nondot.org/sabre/
http://llvm.org/

I find a bug in document llvm/docs/WritingAnLLVMPass.html#debughints

Since the PassManager class is in the namespace llvm, we should use command

(gdb) break llvm::PassManager::run

to set breakpoint. Otherwise we get error message:

(gdb) break PassManager::run
Can't find member of namespace, class, struct, or union named
"PassManager::run"
Hint: try 'PassManager::run<TAB> or 'PassManager::run<ESC-?>
(Note leading single quote.)

The patch is:

--- WritingAnLLVMPass.html      2006-03-14 13:39:39.000000000 +0800
+++ WritingAnLLVMPass-new.html  2006-09-28 21:06:36.000000000 +0800
@@ -1475,7 +1475,7 @@
 want:</p>

 <pre>
-(gdb) <b>break PassManager::run</b>
+(gdb) <b>break llvm::PassManager::run</b>
 Breakpoint 1 at 0x2413bc: file Pass.cpp, line 70.
 (gdb) <b>run test.bc -load $(LLVMTOP)/llvm/Debug/lib/[libname].so
-[passoption]</b>
 Starting program: opt test.bc -load $(LLVMTOP)/llvm/Debug/lib/[libname].so
-[passoption]