Izaron added inline comments.
================ Comment at: clang/lib/AST/ExprConstant.cpp:12452 + int Ilogb; + if (APFloat::opStatus St = ilogb(F, Ilogb); !isConstantOpStatus(St)) + return false; ---------------- aaron.ballman wrote: > jcranmer-intel wrote: > > `long double` is `ppc_fp128` on at least some PPC targets, and while I'm > > not entirely certain of what `ilogb` properly returns in the corner cases > > of the `ppc_fp128`, I'm not entirely confident that the implementation of > > `APFloat` is correct in those cases. I'd like someone with PPC background > > to comment in here. > Paging @hubert.reinterpretcast for help finding a good person to comment on > the PPC questions. @jcranmer-intel constexpr evaluation is quite machine-/target-independent. Clang evaluates it based on its **internal** representation of float variables. [[ https://github.com/llvm/llvm-project/blob/2e5bf4da99a2f8d3d4bb4f1a4d1ed968a01e8f02/llvm/include/llvm/ADT/APFloat.h#L1256 | int ilogb ]] uses `Arg.getIEEE()`, that [[ https://github.com/llvm/llvm-project/blob/2e5bf4da99a2f8d3d4bb4f1a4d1ed968a01e8f02/llvm/include/llvm/ADT/APFloat.h#L819-L825 | returns Clang's internal float representation ]]. Whichever float semantics is being used, [[ https://github.com/llvm/llvm-project/blob/2e5bf4da99a2f8d3d4bb4f1a4d1ed968a01e8f02/llvm/lib/Support/APFloat.cpp#L54-L61 | minExponent and maxExponent are representable as APFloatBase::ExponentType ]], which is `int32_t`: ``` /// A signed type to represent a floating point numbers unbiased exponent. typedef int32_t ExponentType; ``` We already use `int ilogb` in some constexpr evaluation code: [[ https://github.com/llvm/llvm-project/blob/2e5bf4da99a2f8d3d4bb4f1a4d1ed968a01e8f02/clang/lib/AST/ExprConstant.cpp#L14592 | link ]], it is working correct because it is working on Clang's float representations. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D136568/new/ https://reviews.llvm.org/D136568 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
