[libc++] Fix one case in saturate_cast.pass.cpp for 64-bit on z/OS

[zibi2]

On z/OS int128 is disabled causing one of the cases in saturate_cast.pass.cpp to fail. The failure is only in 64-bit mode.
In this case the std::numeric_limits<long long int>::max() is within std::numeric_limits<unsigned long int>::min()
and std::numeric_limits<unsigned long int>::max() therefore, saturate_cast( sBigMax) == LONG_MAX and not ULONG_MAX as original test.

In 32-bit, saturate_cast<unsigned long int>( sBigMax) == ULONG_MAX like on other platforms where int128 is enabled.

This PR is required to pass this test case on z/OS and possibly on other platforms where int128 is not supported/enabled.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: None (zibi2)

Changes

On z/OS int128 is disabled causing one of the cases in saturate_cast.pass.cpp to fail. The failure is only in 64-bit mode.
In this case the std::numeric_limits<long long int>::max() is within std::numeric_limits<unsigned long int>::min()
and std::numeric_limits<unsigned long int>::max() therefore, saturate_cast<unsigned long int>( sBigMax) == LONG_MAX and not ULONG_MAX as original test.

In 32-bit, saturate_cast<unsigned long int>( sBigMax) == ULONG_MAX like on other platforms where int128 is enabled.

This PR is required to pass this test case on z/OS and possibly on other platforms where int128 is not supported/enabled.

---

Full diff: https://github.com/llvm/llvm-project/pull/86724.diff

1 Files Affected:

• (modified) libcxx/test/std/numerics/numeric.ops/numeric.ops.sat/saturate_cast.pass.cpp (+1-1)

diff --git a/libcxx/test/std/numerics/numeric.ops/numeric.ops.sat/saturate_cast.pass.cpp b/libcxx/test/std/numerics/numeric.ops/numeric.ops.sat/saturate_cast.pass.cpp
index c06a9ed2d5cb42..59f397d5c0ee76 100644
--- a/libcxx/test/std/numerics/numeric.ops/numeric.ops.sat/saturate_cast.pass.cpp
+++ b/libcxx/test/std/numerics/numeric.ops/numeric.ops.sat/saturate_cast.pass.cpp
@@ -329,7 +329,7 @@ constexpr bool test() {
   { [[maybe_unused]] std::same_as<unsigned long int> decltype(auto) _ = std::saturate_cast<unsigned long int>(sBigMax); }
   assert(std::saturate_cast<unsigned long int>(  sBigMin) == 0UL);       // saturated
   assert(std::saturate_cast<unsigned long int>(    sZero) == 0UL);
-  assert(std::saturate_cast<unsigned long int>(  sBigMax) == ULONG_MAX); // saturated
+  assert(std::saturate_cast<unsigned long int>(  sBigMax) == (sizeof(UIntT)>sizeof(unsigned long int)?ULONG_MAX:LONG_MAX)); // saturated depending on underlying types
 
   { [[maybe_unused]] std::same_as<unsigned long int> decltype(auto) _ = std::saturate_cast<unsigned long int>(uBigMax); }
   assert(std::saturate_cast<unsigned long int>(    uZero) == 0UL);

[ldionne]

LGTM with a formatting nitpick.