[flang] Tighten requirements on some glibc float128 functions

[DavidTruby]

j0l, j1l, jnl, y0l, y1l and ynl are glibc extensions rather than
standard POSIX functions, and so are not available in every Linux libc.
This patch checks if __GLIBC__ and _GNU_SOURCE are defined before using
these functions.

This patch allows the float128 runtime to build with musl libc on Linux.

[vzakhari]

Thank you, David!

[tblah]

Thanks!

[llvmbot]

@llvm/pr-subscribers-flang-runtime

@llvm/pr-subscribers-flang-semantics

Author: David Truby (DavidTruby)

Changes

j0l, j1l, jnl, y0l, y1l and ynl are glibc extensions rather than
standard POSIX functions, and so are not available in every Linux libc.
This patch checks if __GLIBC__ and _GNU_SOURCE are defined before using
these functions.

This patch allows the float128 runtime to build with musl libc on Linux.

---

Full diff: https://github.com/llvm/llvm-project/pull/110651.diff

2 Files Affected:

• (modified) flang/lib/Evaluate/intrinsics-library.cpp (+1-1)
• (modified) flang/runtime/Float128Math/math-entries.h (+6-3)

diff --git a/flang/lib/Evaluate/intrinsics-library.cpp b/flang/lib/Evaluate/intrinsics-library.cpp
index ce9dd6b7b3df86..977705acf7a9f7 100644
--- a/flang/lib/Evaluate/intrinsics-library.cpp
+++ b/flang/lib/Evaluate/intrinsics-library.cpp
@@ -415,7 +415,7 @@ template <> struct HostRuntimeLibrary<double, LibraryVersion::LibmExtensions> {
   static_assert(map.Verify(), "map must be sorted");
 };
 
-#if HAS_FLOAT80 || HAS_LDBL128
+#if defined(__GLIBC__) && (HAS_FLOAT80 || HAS_LDBL128)
 template <>
 struct HostRuntimeLibrary<long double, LibraryVersion::LibmExtensions> {
   using F = FuncPointer<long double, long double>;
diff --git a/flang/runtime/Float128Math/math-entries.h b/flang/runtime/Float128Math/math-entries.h
index 151ed8a09fde0a..47f1993f22d659 100644
--- a/flang/runtime/Float128Math/math-entries.h
+++ b/flang/runtime/Float128Math/math-entries.h
@@ -185,9 +185,6 @@ DEFINE_SIMPLE_ALIAS(Hypot, std::hypot)
 DEFINE_SIMPLE_ALIAS(Ilogb, std::ilogb)
 DEFINE_SIMPLE_ALIAS(Isinf, std::isinf)
 DEFINE_SIMPLE_ALIAS(Isnan, std::isnan)
-DEFINE_SIMPLE_ALIAS(J0, j0l)
-DEFINE_SIMPLE_ALIAS(J1, j1l)
-DEFINE_SIMPLE_ALIAS(Jn, jnl)
 DEFINE_SIMPLE_ALIAS(Ldexp, std::ldexp)
 DEFINE_SIMPLE_ALIAS(Lgamma, std::lgamma)
 DEFINE_SIMPLE_ALIAS(Llround, std::llround)
@@ -204,9 +201,15 @@ DEFINE_SIMPLE_ALIAS(Tan, std::tan)
 DEFINE_SIMPLE_ALIAS(Tanh, std::tanh)
 DEFINE_SIMPLE_ALIAS(Tgamma, std::tgamma)
 DEFINE_SIMPLE_ALIAS(Trunc, std::trunc)
+
+#if defined(__GLIBC__) && defined(_GNU_SOURCE)
+DEFINE_SIMPLE_ALIAS(J0, j0l)
+DEFINE_SIMPLE_ALIAS(J1, j1l)
+DEFINE_SIMPLE_ALIAS(Jn, jnl)
 DEFINE_SIMPLE_ALIAS(Y0, y0l)
 DEFINE_SIMPLE_ALIAS(Y1, y1l)
 DEFINE_SIMPLE_ALIAS(Yn, ynl)
+#endif
 
 // Use numeric_limits to produce infinity of the right type.
 #define F128_RT_INFINITY \

[DavidTruby]

I think we need a check on the definitions as well for some platforms so I've added that