[clang] [Driver] Add check for -mstack-alignment (PR #143124)

[Feng Zou via cfe-commits]

https://github.com/fzou1 created 
https://github.com/llvm/llvm-project/pull/143124

An error message will be emitted if the wrong value is passed to 
-mstack-alignment option.

>From 688405f851d3685e588b4797314377a1d5d5c124 Mon Sep 17 00:00:00 2001
From: Feng Zou <feng....@intel.com>
Date: Fri, 6 Jun 2025 18:21:30 +0800
Subject: [PATCH] [Driver] Add check for -mstack-alignment

An error message will be emitted if the wrong value is passed to
-mstack-alignment option.
---
 clang/lib/Driver/ToolChains/Clang.cpp | 14 +++++++++++---
 clang/test/Driver/stack-alignment.c   | 11 +++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 clang/test/Driver/stack-alignment.c

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp 
b/clang/lib/Driver/ToolChains/Clang.cpp
index 80dd72a23a673..290c10e5ea6cb 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7047,9 +7047,17 @@ void Clang::ConstructJob(Compilation &C, const JobAction 
&JA,
   Args.addOptInFlag(CmdArgs, options::OPT_mstackrealign,
                     options::OPT_mno_stackrealign);
 
-  if (Args.hasArg(options::OPT_mstack_alignment)) {
-    StringRef alignment = Args.getLastArgValue(options::OPT_mstack_alignment);
-    CmdArgs.push_back(Args.MakeArgString("-mstack-alignment=" + alignment));
+  if (const Arg *A = Args.getLastArg(options::OPT_mstack_alignment)) {
+    StringRef Value = A->getValue();
+    int64_t Alignment = 0;
+    if (Value.getAsInteger(10, Alignment) || Alignment < 0)
+      D.Diag(diag::err_drv_invalid_argument_to_option)
+          << Value << A->getOption().getName();
+    else if (Alignment & (Alignment - 1))
+      D.Diag(diag::err_drv_alignment_not_power_of_two)
+          << A->getAsString(Args) << Value;
+    else
+      CmdArgs.push_back(Args.MakeArgString("-mstack-alignment=" + Value));
   }
 
   if (Args.hasArg(options::OPT_mstack_probe_size)) {
diff --git a/clang/test/Driver/stack-alignment.c 
b/clang/test/Driver/stack-alignment.c
new file mode 100644
index 0000000000000..e1e62c05c32ab
--- /dev/null
+++ b/clang/test/Driver/stack-alignment.c
@@ -0,0 +1,11 @@
+// RUN: not %clang -### -mstack-alignment=-1 %s 2>&1 | FileCheck %s 
--check-prefix=CHECK_NEG_1
+// RUN: %clang -### -mstack-alignment=0 %s 2>&1 | FileCheck %s 
--check-prefix=CHECK_0
+// RUN: %clang -### -mstack-alignment=1 %s 2>&1 | FileCheck %s 
--check-prefix=CHECK_1
+// RUN: %clang -### -mstack-alignment=4 %s 2>&1 | FileCheck %s 
--check-prefix=CHECK_4
+// RUN: not %clang -### -mstack-alignment=5 %s 2>&1 | FileCheck %s 
--check-prefix=CHECK_5
+
+// CHECK_NEG_1: error: invalid argument '-1' to -mstack-alignment=
+// CHECK_0: -mstack-alignment=0
+// CHECK_1: -mstack-alignment=1
+// CHECK_4: -mstack-alignment=4
+// CHECK_5: error: alignment is not a power of 2 in '-mstack-alignment=5'

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