[libc++][test][AIX] Only XFAIL atomic tests for before clang 19 (#94646)

These tests pass on 64-bit. They were fixed by 5fdd094 on 32-bit.
So XFAIL only for 32-bit before clang 19.

Author: jakeegan

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/fetch_add.pass.cpp

@@ -6,9 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
 
+// Older versions of clang have a bug with atomic builtins affecting double and long double.
+// Fixed by 5fdd0948.
+// XFAIL: target=powerpc-ibm-{{.*}} && (clang-17 || clang-18)
+
 // https://github.com/llvm/llvm-project/issues/72893
 // XFAIL: target={{x86_64-.*}} && tsan
 

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/fetch_sub.pass.cpp

@@ -6,9 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
 
+// Older versions of clang have a bug with atomic builtins affecting double and long double.
+// Fixed by 5fdd0948.
+// XFAIL: target=powerpc-ibm-{{.*}} && (clang-17 || clang-18)
+
 // https://github.com/llvm/llvm-project/issues/72893
 // XFAIL: target={{x86_64-.*}} && tsan
 

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.minus_equals.pass.cpp

@@ -6,9 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
 
+// Older versions of clang have a bug with atomic builtins affecting double and long double.
+// Fixed by 5fdd0948.
+// XFAIL: target=powerpc-ibm-{{.*}} && (clang-17 || clang-18)
+
 // floating-point-type operator-=(floating-point-type) volatile noexcept;
 // floating-point-type operator-=(floating-point-type) noexcept;
 

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.plus_equals.pass.cpp

@@ -6,9 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
 
+// Older versions of clang have a bug with atomic builtins affecting double and long double.
+// Fixed by 5fdd0948.
+// XFAIL: target=powerpc-ibm-{{.*}} && (clang-17 || clang-18)
+
 // floating-point-type operator+=(floating-point-type) volatile noexcept;
 // floating-point-type operator+=(floating-point-type) noexcept;