[cfe-commits] r110660 - in /cfe/trunk: lib/CodeGen/CGDebugInfo.cpp lib/CodeGen/CGDebugInfo.h lib/CodeGen/CGExprScalar.cpp lib/CodeGen/CodeGenFunction.cpp lib/CodeGen/CodeGenFunction.h test/CodeGen/2010-08-10-DbgConstant.c

[Chris Lattner]

On Aug 10, 2010, at 12:24 AM, Devang Patel wrote:
> Author: dpatel
> Date: Tue Aug 10 02:24:25 2010
> New Revision: 110660
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=110660&view=rev
> Log:
> Even if a constant's evaluated value is used, emit debug info for the constant variable.

Ok, a couple of comments.

> +++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp Tue Aug 10 02:24:25 2010
> @@ -1801,6 +1801,17 @@
>                                     true/*definition*/, Var);
> }
> 
> +void CGDebugInfo::EmitGlobalVariable(llvm::Constant *C, const ValueDecl *VD,
> +                                     CGBuilderTy &Builder) {

VD should come first, because it is the global variable you're emitting the debug info for, the constant is secondary.  Also, C should be named "Initializer" and/or you should add a doxygen comment explaining what this does.

> +++ cfe/trunk/lib/CodeGen/CGDebugInfo.h Tue Aug 10 02:24:25 2010
> @@ -181,6 +181,10 @@
>   /// EmitGlobalVariable - Emit information about an objective-c interface.
>   void EmitGlobalVariable(llvm::GlobalVariable *GV, ObjCInterfaceDecl *Decl);
> 
> +  /// EmitGlobalVariable - Emit information about a constant.
> +  void EmitGlobalVariable(llvm::Constant *C, const ValueDecl *VD, 
> +                          CGBuilderTy &Builder);

This comment seems contradictory.  Are you emitting debug info for a global variable or a constant?

> +++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Tue Aug 10 02:24:25 2010
> @@ -149,6 +149,7 @@
>     Expr::EvalResult Result;
>     if (E->Evaluate(Result, CGF.getContext()) && Result.Val.isInt()) {
>       assert(!Result.HasSideEffects && "Constant declref with side-effect?!");
> +      CGF.EmitDeclRefExprDbgValue(E, Result.Val);
>       return llvm::ConstantInt::get(VMContext, Result.Val.getInt());

This is the only caller of CGF.EmitDeclRefExprDbgValue.  Please pass the created ConstantInt to it instead of passing the APValue.

> +void CodeGenFunction::EmitDeclRefExprDbgValue(const DeclRefExpr *E, 
> +                                              const APValue &AV) {
> +  CGDebugInfo *Dbg = getDebugInfo();
> +  if (!Dbg) return;
> +
> +  llvm::Constant *C = NULL;
> +  if (AV.isInt())
> +    C = llvm::ConstantInt::get(getLLVMContext(), AV.getInt());
> +  else if (AV.isFloat())
> +    C = llvm::ConstantFP::get(getLLVMContext(), AV.getFloat());

Passing the constantint will eliminate this code.

> +  if (C)
> +    Dbg->EmitGlobalVariable(C, E->getDecl(), Builder);

This is calling EmitGlobalVariable *every* time a constant is codegen'd in the code.  In your example, ro+ro+ro+ro will cause the global to get emitted 4 times.  I realize that MDNodes do autouniquing, but doesn't this sound inefficient?

-Chris

> +}
> 
> Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=110660&r1=110659&r2=110660&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
> +++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Tue Aug 10 02:24:25 2010
> @@ -41,6 +41,7 @@
> }
> 
> namespace clang {
> +  class APValue;
>   class ASTContext;
>   class CXXDestructorDecl;
>   class CXXTryStmt;
> @@ -1372,7 +1373,7 @@
>   LValue EmitStmtExprLValue(const StmtExpr *E);
>   LValue EmitPointerToDataMemberBinaryExpr(const BinaryOperator *E);
>   LValue EmitObjCSelectorLValue(const ObjCSelectorExpr *E);
> -  
> +  void   EmitDeclRefExprDbgValue(const DeclRefExpr *E, const APValue &AV);
>   //===--------------------------------------------------------------------===//
>   //                         Scalar Expression Emission
>   //===--------------------------------------------------------------------===//
> 
> Added: cfe/trunk/test/CodeGen/2010-08-10-DbgConstant.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/2010-08-10-DbgConstant.c?rev=110660&view=auto
> ==============================================================================
> --- cfe/trunk/test/CodeGen/2010-08-10-DbgConstant.c (added)
> +++ cfe/trunk/test/CodeGen/2010-08-10-DbgConstant.c Tue Aug 10 02:24:25 2010
> @@ -0,0 +1,5 @@
> +// RUN: %clang_cc1 -S -emit-llvm -g  %s -o - | grep DW_TAG_constant
> +
> +static const unsigned int ro = 201;
> +void bar(int);
> +void foo() { bar(ro); }
> 
> 
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