[clang] [Driver] -fno-plt: warn for unsupported targets (PR #124081)

[Fangrui Song via cfe-commits]

https://github.com/MaskRay updated https://github.com/llvm/llvm-project/pull/124081

>From a38b6aecebba895f11c967cc83f9e98bda359ffe Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Wed, 22 Jan 2025 23:03:41 -0800
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.5-bogner
---
 clang/lib/Driver/ToolChains/Clang.cpp | 5 ++---
 clang/test/Driver/fno-plt.c           | 7 +++++++
 2 files changed, 9 insertions(+), 3 deletions(-)
 create mode 100644 clang/test/Driver/fno-plt.c

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 33f08cf28feca1..5df58005a52373 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6141,9 +6141,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-fno-direct-access-external-data");
   }
 
-  if (Args.hasFlag(options::OPT_fno_plt, options::OPT_fplt, false)) {
-    CmdArgs.push_back("-fno-plt");
-  }
+  if (Triple.isOSBinFormatELF())
+    Args.addOptOutFlag(CmdArgs, options::OPT_fplt, options::OPT_fno_plt);
 
   // -fhosted is default.
   // TODO: Audit uses of KernelOrKext and see where it'd be more appropriate to
diff --git a/clang/test/Driver/fno-plt.c b/clang/test/Driver/fno-plt.c
new file mode 100644
index 00000000000000..d5189e2b508b2a
--- /dev/null
+++ b/clang/test/Driver/fno-plt.c
@@ -0,0 +1,7 @@
+// RUN: %clang -### -c --target=aarch64 -fno-plt -Werror %s 2>&1 | FileCheck %s
+// RUN: %clang -### -c --target=aarch64 -fno-plt -fplt -Werror %s 2>&1 | FileCheck %s --check-prefix=NO
+// RUN: %clang -### -c --target=aarch64-windows -fno-plt %s 2>&1 | FileCheck %s --check-prefixes=WARN,NO
+
+// WARN: warning: argument unused during compilation: '-fno-plt' [-Wunused-command-line-argument]
+// CHECK: "-fno-plt"
+// NO-NOT: "-fno-plt"