How to use WhileStmt to implement while loop in LLVM

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#1

Dear All,

I have a question

How could I use WhileStmt class in Stmt.h

http://clang.llvm.org/doxygen/Stmt_8h_source.html

to implement while loop like while(i==1){} that is required to be inserted

For example, Convert x++; y++; to x++; while(i=1){} y++;

from the class’s constructor:

WhileStmt(ASTContext &C, VarDecl *Var, Expr *cond, Stmt *body,SourceLocation WL);
//I know C --> 1
//Var--> i
//cond --> =
//body --> NOP
//WL --> ??

but how to implement these terms in LLVM pass? and what’s the SourceLocation?

Thanks

#2

Rasha Omar wrote:

Dear All,

I have a question

How could I use |WhileStmt class| in Stmt.h

http://clang.llvm.org/doxygen/Stmt_8h_source.html

to implement |while loop| like |while(i==1){}| that is required to be
inserted

For example, Convert x++; y++; to x++; while(i=1){} y++;

from the class's constructor:

>WhileStmt(ASTContext &C, VarDecl *Var, Expr *cond, Stmt *body,SourceLocation WL);
//I know C --> 1
//Var--> i
//cond --> =
//body --> NOP
//WL --> ??|

but how to implement these terms in LLVM pass? and what's the
SourceLocation?

Do you actually mean LLVM pass? Or are you working inside clang (for example, on a source code rewriter)? If so, email cfe-dev instead.

Nick

#3

No, I need to use it in LLVM pass. Could it work?

#4

Rasha Omar wrote:

No, I need to use it in LLVM pass. Could it work?

No. The language available at llvm-time is the one in llvm.org/docs/LangRef.html which doesn't have a while statement. For one obvious example, how would this work if the input language wasn't C/C++ to begin with?

If you absolutely need to do this for a non-production-quality project (ie., research project or other one-off), you can jam the WhileStmt pointer value as an integer into a metadata node when doing IRGen from clang, and reinterpret it back on the llvm side. We will not accept patches which do this sort of thing, and this is very much warranty void territory. Your generated IR will not work if you try to run llvm tools outside the clang process.

Nick