[cfe-commits] r147306 - /cfe/trunk/lib/Analysis/CFG.cpp

[Xu Zhongxing]

Hi Ted,

I would like to add elidable CXXConstructExpr as block-expr. Since 
expression

(CXXConstructExpr 0x3268658 <col:5, col:7> 'class A''void (const class A 
&) throw()' elidable

converts an lvalue 'const class A &' to an rvalue 'class A'. This step 
is useful during AST evaluation.

So is this patch ok?

Index: lib/Analysis/CFG.cpp
===================================================================
--- lib/Analysis/CFG.cpp    (revision 147306)
+++ lib/Analysis/CFG.cpp    (working copy)
@@ -2768,8 +2768,7 @@
  CFGBlock *CFGBuilder::VisitCXXConstructExpr(CXXConstructExpr *C,
                                              AddStmtChoice asc) {
    autoCreateBlock();
-  if (!C->isElidable() && asc.alwaysAdd(*this, C))
-    appendStmt(Block, C);
+  appendStmt(Block, C);

    return VisitChildren(C);
  }

于 2012/1/4 9:40, Xu Zhongxing 写道:
> AST does have all these information in it. It's just the linearized CFG
> reverses the order in which we see the AST nodes.
>
> 于 2012/1/4 5:48, Ted Kremenek 写道:
>> Interesting.  If the AST doesn't have enough information for the analyzer (and other clients) to do a good job here, then I think it would be reasonable to investigate pushing an AST-level change to fix the issue.
>>
>> On Dec 29, 2011, at 4:03 AM, Xu Zhongxing wrote:
>>
>>> I admit this is not a correct solution. If I set add CXXConstructExpr bit in the CFG::BuildOptions to false, there exist some cases CXXConstructExpr is not added as block-level expr, where it should.
>>>
>>> Linearizing the CFG is great idea. I already enjoy it very much.
>>>
>>> We need to provide more information to CXXConstructExpr: its destination object (a variable or a temporary object that should be conjured) and its kind (base,complete).
>>>
>>> For the destination object, we could always conjure a temporary object and use LazyCompoundVal to bind the real object being constructed when we later see it.
>>>
>>> 于 2011/12/29 13:59, Ted Kremenek 写道:
>>>> Hi Zhongxing,
>>>>
>>>> I don't understand how this is actually fixing (1) or (2).  Can you explain?  We're moving to a place where we will likely linearize the entire CFG (this is already the case for the static analyzer), so it would be great to find a solution to (1) or (2) that doesn't depend on whether or not CXXConstructExpr is a block-level expression.
>>>>
>>>> Thanks,
>>>> Ted
>>>>
>>>> On Dec 27, 2011, at 8:38 PM, Zhongxing Xu wrote:
>>>>
>>>>> Author: zhongxingxu
>>>>> Date: Tue Dec 27 22:38:46 2011
>>>>> New Revision: 147306
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=147306&view=rev
>>>>> Log:
>>>>> Enable the user to control whether CXXConstructExpr will be added as a
>>>>> block-level expr. Currently CXXConstructExpr is always added as a block-level
>>>>> expr. This caused two problems for the analyzer (and potentially for the
>>>>> CFG-based codegen).
>>>>> 1. We have no way to know whether a ctor call is base or complete.
>>>>> 2. We have no way to know the destination object being contructed.
>>>>>
>>>>> Modified:
>>>>>     cfe/trunk/lib/Analysis/CFG.cpp
>>>>>
>>>>> Modified: cfe/trunk/lib/Analysis/CFG.cpp
>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/CFG.cpp?rev=147306&r1=147305&r2=147306&view=diff
>>>>> ==============================================================================
>>>>> --- cfe/trunk/lib/Analysis/CFG.cpp (original)
>>>>> +++ cfe/trunk/lib/Analysis/CFG.cpp Tue Dec 27 22:38:46 2011
>>>>> @@ -2768,7 +2768,7 @@
>>>>> CFGBlock *CFGBuilder::VisitCXXConstructExpr(CXXConstructExpr *C,
>>>>>                                              AddStmtChoice asc) {
>>>>>    autoCreateBlock();
>>>>> -  if (!C->isElidable())
>>>>> +  if (!C->isElidable()&&    asc.alwaysAdd(*this, C))
>>>>>      appendStmt(Block, C);
>>>>>
>>>>>    return VisitChildren(C);
>>>>>
>>>>>
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