[clang] [SystemZ][zOS] disable _Float16 support on z/OS (PR #145532)

[Sean Perry via cfe-commits]

https://github.com/perry-ca created https://github.com/llvm/llvm-project/pull/145532

The new half float type (aka _Float16 ) isn't supported on z/OS.

>From 42c7e584ab1faa7dd07921a7de79d96d052a6949 Mon Sep 17 00:00:00 2001
From: Sean Perry <perry at ca.ibm.com>
Date: Tue, 24 Jun 2025 11:26:57 -0400
Subject: [PATCH] disable _Float16 support on z/OS

---
 clang/lib/Basic/Targets/SystemZ.h | 5 +++--
 clang/test/Sema/Float16.c         | 1 +
 clang/test/SemaCXX/Float16.cpp    | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Basic/Targets/SystemZ.h b/clang/lib/Basic/Targets/SystemZ.h
index 1f69530c4757f..bb7b6640570a5 100644
--- a/clang/lib/Basic/Targets/SystemZ.h
+++ b/clang/lib/Basic/Targets/SystemZ.h
@@ -76,6 +76,7 @@ class LLVM_LIBRARY_VISIBILITY SystemZTargetInfo : public TargetInfo {
     MinGlobalAlign = 16;
     HasUnalignedAccess = true;
     if (Triple.isOSzOS()) {
+      HasFloat16 = false;
       if (Triple.isArch64Bit()) {
         AddrSpaceMap = &ZOSAddressMap;
       }
@@ -89,6 +90,8 @@ class LLVM_LIBRARY_VISIBILITY SystemZTargetInfo : public TargetInfo {
       resetDataLayout("E-m:l-p1:32:32-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-"
                       "a:8:16-n32:64");
     } else {
+      // Support _Float16.
+      HasFloat16 = true;
       TLSSupported = true;
       resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64"
                       "-v128:64-a:8:16-n32:64");
@@ -102,8 +105,6 @@ class LLVM_LIBRARY_VISIBILITY SystemZTargetInfo : public TargetInfo {
     // and instead the backend will promote each half operation to float
     // individually.
     HasLegalHalfType = false;
-    // Support _Float16.
-    HasFloat16 = true;
 
     HasStrictFP = true;
   }
diff --git a/clang/test/Sema/Float16.c b/clang/test/Sema/Float16.c
index 9269a0ded4eb9..2830213b6099f 100644
--- a/clang/test/Sema/Float16.c
+++ b/clang/test/Sema/Float16.c
@@ -6,6 +6,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -triple aarch64-linux-gnu %s -DHAVE
 // RUN: %clang_cc1 -fsyntax-only -verify -triple riscv32 %s -DHAVE
 // RUN: %clang_cc1 -fsyntax-only -verify -triple riscv64 %s -DHAVE
+// RUN: %clang_cc1 -fsyntax-only -verify -triple s390x-ibm-zos %s
 
 #ifndef HAVE
 // expected-error at +2{{_Float16 is not supported on this target}}
diff --git a/clang/test/SemaCXX/Float16.cpp b/clang/test/SemaCXX/Float16.cpp
index 61b02a50687b9..9646a8d0c317f 100644
--- a/clang/test/SemaCXX/Float16.cpp
+++ b/clang/test/SemaCXX/Float16.cpp
@@ -4,7 +4,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -triple spir-unknown-unknown %s -DHAVE
 // RUN: %clang_cc1 -fsyntax-only -verify -triple armv7a-linux-gnu %s -DHAVE
 // RUN: %clang_cc1 -fsyntax-only -verify -triple aarch64-linux-gnu %s -DHAVE
-
+// RUN: %clang_cc1 -fsyntax-only -verify -triple s390x-ibm-zos %s
 #ifdef HAVE
 // expected-no-diagnostics
 #endif // HAVE