[PATCH] D72778: [Matrix] Add __builtin_matrix_transpose to Clang.

[John McCall via Phabricator via cfe-commits]

rjmccall accepted this revision.
rjmccall added a comment.
This revision is now accepted and ready to land.

Thanks, LGTM with the given testing suggestion.



================
Comment at: clang/lib/Sema/SemaChecking.cpp:15051
+
+  Expr *Arg = TheCall->getArg(0);
+  if (!Arg->getType()->isConstantMatrixType()) {
----------------
fhahn wrote:
> rjmccall wrote:
> > fhahn wrote:
> > > rjmccall wrote:
> > > > When a builtin has custom type-checking (`t`), you need to handle placeholders in the operands yourself, just like you would for an operator.
> > > I added placeholder handling and added additional tests.
> > Oh, I'm sorry, I gave you poor advice: you do need to handle placeholders, but more generally than that, you need an r-value.   Since you aren't doing any further conversions, you just need to call DefaultLValueConversion, which will also handle placeholders for you.
> > 
> > You will also need to store the checked argument back into the call, which you can only really test with an IRGen test.  This is one of the few places where we do actually directly mutate the AST.
> Oh right, I wasn't sure about whether we need DefaultLValueConversion here or not. I tried to construct a C/C++ test case that would actually require it, but couldn't come up with a test. In any case, I updated it to use `DefaultLvalueConversion` instead and also adjust the argument before returning the updated call.
IRGen is pretty lenient about missing LValueToRValue conversions because of the way it peepholes loads from complex l-value expressions.  But if you have basic `constexpr` stuff working in Sema, I think you can test this with lambdas.  A reference to a `constexpr` variable that's immediately loaded from is not an ODR-use, which means that within a lambda it doesn't result in a capture.  So a test like this should work, and it wouldn't if you didn't generate the LValueToRValue conversion in Sema.   (I think it doesn't actually test that the LValueToRValue conversions is actually added to the AST, though, just that you actually generated the AST node.)

```
  constexpr double4x4 m = {};
  [] { return __builtin_matrix_transpose(m); }
```


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D72778