[libc-commits] [libc] [libc][i386] FPBit support for 96b long double (PR #115084)

[via libc-commits]

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@@ -127,7 +127,18 @@ template <> struct FPLayout<FPType::IEEE754_Binary128> {
 };
 
 template <> struct FPLayout<FPType::X86_Binary80> {
+// x86_64
+#if __SIZEOF_LONG_DOUBLE__ == 16
   using StorageType = UInt128;
+// i386-linux-gnu
+#elif __SIZEOF_LONG_DOUBLE__ == 12
+  using StorageType = UInt<__SIZEOF_LONG_DOUBLE__ * CHAR_BIT>;
+#else
+// TODO: https://github.com/llvm/llvm-project/issues/115184
+// Android i386 uses `long double == double` i.e. `sizeof(long double) == 8`
+// https://developer.android.com/ndk/guides/abis#x86
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lntue wrote:

Now that thinking more about it, I would like to dictate using `UInt128` for 80-bit floating point whenever `__SIZEOF_LONG_DOUBLE__ != 12`.  So that when we emulate 80-bit floating points on targets other than i386, we will always use 128-bit.  For Android, Windows, and MacOS where long double is double, it will be taken care of by `LIBC_TYPES_LONG_DOUBLE_IS_DOUBLE`, and so this specialization is not used for `FPBits<long double>`.

https://github.com/llvm/llvm-project/pull/115084