[PowerPC] Exclude frexp(long double) on linux

[lei]

Summary

PowerPC on linux currently don't have support for lowering long double for
frexp(). Removing the tests until implementation is provided.

[Mordante]

libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp

61

I prefer an #if ! defined(__LONG_DOUBLE_IBM128__) here instead of moving this line. That keeps the order as expected.

[lei]

Keep original order

[Mordante]

Thanks, LGTM from libc++'s perspective!

I don't know whether the used definition __LONG_DOUBLE_IBM128__ is correct, can one of the PowerPC experts validate that? Please wait for an approval of one of the PowerPC experts before landing.

[amyk]

I think this LGTM. __LONG_DOUBLE_IBM128__ is what we define (on Linux) when we're dealing with the ppcf128 type.

libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp

#define ASSERT_NOT_CONSTEXPR_CXX23(Expr)                                                                               \
   ASSERT_NOT_CONSTEXPR_CXX23(std::div(13, 5).rem == 3);
   ASSERT_NOT_CONSTEXPR_CXX23(std::div(13L, 5L).rem == 3L);
   ASSERT_NOT_CONSTEXPR_CXX23(std::div(13LL, 5LL).rem == 3LL);
   ASSERT_NOT_CONSTEXPR_CXX23(std::ldiv(13L, 5L).rem == 3L);
   ASSERT_NOT_CONSTEXPR_CXX23(std::lldiv(13LL, 5LL).rem == 3LL);
 
   ASSERT_NOT_CONSTEXPR_CXX23(std::frexp(0.0f, &DummyInt) == 0.0f);
   ASSERT_NOT_CONSTEXPR_CXX23(std::frexp(0.0, &DummyInt) == 0.0);
-  ASSERT_NOT_CONSTEXPR_CXX23(std::frexp(0.0L, &DummyInt) == 0.0L);
   ASSERT_NOT_CONSTEXPR_CXX23(std::frexpf(0.0f, &DummyInt) == 0.0f);
+
+//FIXME: currently linux powerpc does not support this expansion
+// since 0.0L lowers to ppcf128 and special handling is required.
+#if ! defined(__LONG_DOUBLE_IBM128__)
+  ASSERT_NOT_CONSTEXPR_CXX23(std::frexp(0.0L, &DummyInt) == 0.0L);
   ASSERT_NOT_CONSTEXPR_CXX23(std::frexpl(0.0L, &DummyInt) == 0.0L);
+#endif
 
   ASSERT_NOT_CONSTEXPR_CXX23(std::ilogb(1.0f) == 0);
   ASSERT_NOT_CONSTEXPR_CXX23(std::ilogb(1.0) == 0);
   ASSERT_NOT_CONSTEXPR_CXX23(std::ilogb(1.0L) == 0);
   ASSERT_NOT_CONSTEXPR_CXX23(std::ilogbf(1.0f) == 0);
   ASSERT_NOT_CONSTEXPR_CXX23(std::ilogbl(1.0L) == 0);
 
   ASSERT_NOT_CONSTEXPR_CXX23(std::ldexp(1.0f, 1) == 2.0f);