rjmccall added inline comments.

================
Comment at: clang/lib/Sema/SemaTemplateDeduction.cpp:2143
+                return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
+                                                     DimExpr, Info, Deduced);
+            } else if (const ConstantMatrixType *ConstantMatrixArg =
----------------
fhahn wrote:
> rjmccall wrote:
> > fhahn wrote:
> > > rjmccall wrote:
> > > > I'm curious why this extra check is necessary vs. just calling 
> > > > `DeduceNonTypeTemplateArgument` with `DimExpr` unconditionally.
> > > The code can indeed be quite simplified if we can get a row/column 
> > > expression for ConstantMatrixType as well. 
> > > 
> > > I've refactored the code to also keep the original row/column expression 
> > > in ConstantMatrixType. The new code here is much more compact as the cost 
> > > of increasing the size of ConstantMatrixType. I am not sure if the bigger 
> > > size is a concern, but I would expect that it would not matter much in 
> > > practice. 
> > > 
> > > If it is not a concern, I would further refactor the code and move the 
> > > expressions to MatrixType (which would further simplify the lambdas 
> > > here). The main difference between ConstantMatrixType and 
> > > DependentSizedMatrixType would be that ConstantMatrixTpye would also 
> > > store the dimensions as integers (for easier/faster access). What do you 
> > > think?
> > > 
> > > Alternatively we could potentially construct a new ConstantExpr from the 
> > > integer dimensions in the lambda. Or keep the more clunky accessor 
> > > lambdas.
> > Eh, I'm torn about storing the expressions in `ConstantMatrixType`.  It's 
> > probably true that we wouldn't have a ton of these types and so the overall 
> > overhead might be negligible.  However, I think that if we choose to 
> > represent things this way, we probably ought to make "pristine" new 
> > `IntegerLiteral` expressions instead of remembering the original 
> > expressions, because we don't want weird syntactic quirks of the first 
> > matrix type we see to become embedded in the type forever.  We also run the 
> > risk of actually propagating those expressions around and getting bad 
> > diagnostics that point unexpectedly back at the first place that wrote a 
> > matrix type (or at the null location of a pristine literal) because of 
> > uniquing.  So I think it might be better to just continue to define away 
> > those problems by not storing expressions.
> Sounds good to me. Should I update the code here to use the separate lambdas 
> again or would you prefer creating temporary expressions for the integer case?
I think I would prefer lambdas (or member pointers).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72281/new/

https://reviews.llvm.org/D72281



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