[PATCH] D53738: [Fixed Point Arithmetic] Fixed Point Addition

[Bevin Hansson via Phabricator via cfe-commits]

ebevhan added inline comments.


================
Comment at: clang/lib/Sema/SemaExpr.cpp:1304
+    RHSTy = ResultTy;
+  }
+
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rjmccall wrote:
> Hmm.  So adding a signed integer to an unsigned fixed-point type always converts the integer to unsigned?  That's a little weird, but only because the fixed-point rule seems to be the other way.  Anyway, I assume it's not a bug in the spec.
`handleFixedPointConversion` only calculates the result type of the expression, not the calculation type. The final result type of the operation will be the unsigned fixed-point type, but the calculation itself will be done in a signed type with enough precision to represent both the signed integer and the unsigned fixed-point type. 

Though, if the result ends up being negative, the final result is undefined unless the type is saturating. I don't think there is a test for the saturating case (signed integer + unsigned saturating fixed-point) in the SaturatedAddition tests.


Repository:
  rC Clang

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  https://reviews.llvm.org/D53738/new/

https://reviews.llvm.org/D53738