[PATCH] D122822: [Clang][CodeGen]Add constant array support for __builtin_dump_sturct

[Wang Yihan via Phabricator via cfe-commits]

yihanaa added inline comments.


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Comment at: clang/lib/CodeGen/CGBuiltin.cpp:2048
+                                              QualType Type) {
+  static llvm::DenseMap<QualType, StringRef> Types;
   if (Types.empty()) {
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erichkeane wrote:
> yihanaa wrote:
> > erichkeane wrote:
> > > yihanaa wrote:
> > > > erichkeane wrote:
> > > > > yihanaa wrote:
> > > > > > yihanaa wrote:
> > > > > > > erichkeane wrote:
> > > > > > > > yihanaa wrote:
> > > > > > > > > erichkeane wrote:
> > > > > > > > > > yihanaa wrote:
> > > > > > > > > > > erichkeane wrote:
> > > > > > > > > > > > Instead of this initialization, can we make this a constexpr constructor/collection of some sort and instantiate it inline?  
> > > > > > > > > > > > Instead of this initialization, can we make this a constexpr constructor/collection of some sort and instantiate it inline?  
> > > > > > > > > > > 
> > > > > > > > > > > I don't have a good idea because it relies on Context to get some types like const char *
> > > > > > > > > > We could at minimum do a in inline-initializer instead of the branch below.
> > > > > > > > > I still haven't come up with a good idea to do it😔
> > > > > > > > Hrmph, `DenseMap` doesn't seem to have an init list ctor?!
> > > > > > > > 
> > > > > > > > Since this is a finite, known at compile time list of low 'N', I'd suggest just making it `static std::array<pair<QualType, StringRef>> Types = {{Context.CharTy, "%c"},...`.
> > > > > > > > 
> > > > > > > > Then just doing a llvm::find_if.  The list is small enough I suspect the DenseMap overhead is more than the use of `llvm::find_if`.
> > > > > > > Haha,DenseMap also has no constexpr ctor. I think the time complexity of these two is the same. 
> > > > > > The Context.CharTy... etc. are not static, So we might need a static value instead of it, and compare it with QualType
> > > > > They don't have to be static?  This should do 'magic static' initialization.
> > > > I can't agree more. it might be a type identifier, such as getAsString()'s return value
> > > Actually, I don't think the collection can be static!  When we re-use the same process for multiple TUs, we get a new ASTContext.  SO this would result in us having types that don't necessarily 'match'.  I think this collection/checks need to either be stored in ASTContext, or in an 'if-else' tree here.
> > I also don't think it should be maintained in this place. Shouldn't this be better maintained together with the printf parameter checking part, what do you think?
> I'm unfamiliar with what you mean.
> 
> HOWEVER, the comments by @rsmith and @rjmccall I think are blocking on this feature/functionality anyway.  So we might still wish to refactor this builtin significantly based on what they come up with.
Ah, I think the way I described it is not correct, my thought is, can this getDumpStructFormatSpecifier similar function be maintained in somewhere like FormatString.h😂


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  https://reviews.llvm.org/D122822/new/

https://reviews.llvm.org/D122822