[clang] [Multilib] Expose sanitizer flags as multilib flags for RISC-V (PR #182350)

[via cfe-commits]

https://github.com/pzhengqc updated https://github.com/llvm/llvm-project/pull/182350

>From e7d1ae623387355381ce5e0656e30057638988a8 Mon Sep 17 00:00:00 2001
From: Pengxuan Zheng <pzheng at qti.qualcomm.com>
Date: Thu, 19 Feb 2026 11:30:31 -0800
Subject: [PATCH] [Multilib] Expose shadow call stack as multilib flags for
 RISC-V

This allows multilib selection based on shadow call stack for RISC-V.
---
 clang/lib/Driver/ToolChain.cpp                  | 11 +++++++++--
 clang/test/Driver/print-multi-selection-flags.c |  6 ++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 0eee7f917d2b8..cccb9b1d790e7 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -325,7 +325,8 @@ static void getARMMultilibFlags(const Driver &D, const llvm::Triple &Triple,
 
 static void getRISCVMultilibFlags(const Driver &D, const llvm::Triple &Triple,
                                   const llvm::opt::ArgList &Args,
-                                  Multilib::flags_list &Result) {
+                                  Multilib::flags_list &Result,
+                                  bool hasShadowCallStack) {
   std::string Arch = riscv::getRISCVArch(Args, Triple);
   // Canonicalize arch for easier matching
   auto ISAInfo = llvm::RISCVISAInfo::parseArchString(
@@ -334,6 +335,11 @@ static void getRISCVMultilibFlags(const Driver &D, const llvm::Triple &Triple,
     Result.push_back("-march=" + (*ISAInfo)->toString());
 
   Result.push_back(("-mabi=" + riscv::getRISCVABI(Args, Triple)).str());
+
+  if (hasShadowCallStack)
+    Result.push_back("-fsanitize=shadow-call-stack");
+  else
+    Result.push_back("-fno-sanitize=shadow-call-stack");
 }
 
 Multilib::flags_list
@@ -372,7 +378,8 @@ ToolChain::getMultilibFlags(const llvm::opt::ArgList &Args) const {
   case llvm::Triple::riscv64:
   case llvm::Triple::riscv32be:
   case llvm::Triple::riscv64be:
-    getRISCVMultilibFlags(D, Triple, Args, Result);
+    getRISCVMultilibFlags(D, Triple, Args, Result,
+                          getSanitizerArgs(Args).hasShadowCallStack());
     break;
   default:
     break;
diff --git a/clang/test/Driver/print-multi-selection-flags.c b/clang/test/Driver/print-multi-selection-flags.c
index b1a0a29ec4180..eba00e3278f18 100644
--- a/clang/test/Driver/print-multi-selection-flags.c
+++ b/clang/test/Driver/print-multi-selection-flags.c
@@ -86,6 +86,12 @@
 // RUN: %clang -multi-lib-config=%S/Inputs/multilib/empty.yaml -print-multi-flags-experimental --target=aarch64-none-elf -mbig-endian | FileCheck --check-prefix=CHECK-BIG-ENDIAN %s
 // CHECK-BIG-ENDIAN: -mbig-endian
 
+// RUN: %clang -multi-lib-config=%S/Inputs/multilib/empty.yaml -print-multi-flags-experimental --target=riscv64-none-elf -fsanitize=shadow-call-stack | FileCheck --check-prefix=CHECK-SHADOW-CALL-STACK %s
+// RUN: %clang -multi-lib-config=%S/Inputs/multilib/empty.yaml -print-multi-flags-experimental --target=riscv64-none-elf -fno-sanitize=shadow-call-stack | FileCheck --check-prefix=CHECK-NO-SHADOW-CALL-STACK %s
+// RUN: %clang -multi-lib-config=%S/Inputs/multilib/empty.yaml -print-multi-flags-experimental --target=riscv64-none-elf | FileCheck --check-prefix=CHECK-NO-SHADOW-CALL-STACK %s
+// CHECK-SHADOW-CALL-STACK: -fsanitize=shadow-call-stack
+// CHECK-NO-SHADOW-CALL-STACK: -fno-sanitize=shadow-call-stack
+
 // RUN: %clang -multi-lib-config=%S/Inputs/multilib/empty.yaml -print-multi-flags-experimental --target=riscv32-none-elf -march=rv32g | FileCheck --check-prefix=CHECK-RV32 %s
 // CHECK-RV32: --target=riscv32-unknown-none-elf
 // CHECK-RV32: -mabi=ilp32d