[llvm-branch-commits] [llvm] SafeStack: Emit __safestack_pointer_address call through RuntimeLibcalls (PR #147916)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm updated 
https://github.com/llvm/llvm-project/pull/147916

>From fcf040ce1d0590be1b3dd95ded798c26b1b8f020 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <matthew.arsena...@amd.com>
Date: Thu, 10 Jul 2025 15:09:37 +0900
Subject: [PATCH] SafeStack: Emit __safestack_pointer_address call through
 RuntimeLibcalls

Stop using hardcoded function named and check availability. This only fixes
the forced usage via command line in the pass itself; the implementations
inside of TargetLoweringBase hide additional call emission.
---
 llvm/include/llvm/IR/RuntimeLibcalls.td              |  6 ++++++
 llvm/lib/CodeGen/SafeStack.cpp                       | 10 +++++++++-
 .../NVPTX/safestack-pointer-address-libcall-error.ll | 12 ++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 
llvm/test/Transforms/SafeStack/NVPTX/safestack-pointer-address-libcall-error.ll

diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.td 
b/llvm/include/llvm/IR/RuntimeLibcalls.td
index d4d982922ad9b..65e1adff42d0d 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.td
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.td
@@ -362,6 +362,9 @@ defset list<RuntimeLibcall> LibCalls__OutOfLineAtomic = {
 def STACKPROTECTOR_CHECK_FAIL : RuntimeLibcall;
 def STACK_SMASH_HANDLER : RuntimeLibcall;
 
+// Safe stack
+def SAFESTACK_POINTER_ADDRESS : RuntimeLibcall;
+
 // Deoptimization
 def DEOPTIMIZE : RuntimeLibcall;
 
@@ -702,6 +705,9 @@ foreach lc = LibCalls__atomic in {
 // Stack Protector Fail
 def __stack_chk_fail : RuntimeLibcallImpl<STACKPROTECTOR_CHECK_FAIL>;
 
+// Safe stack.
+def __safestack_pointer_address : 
RuntimeLibcallImpl<SAFESTACK_POINTER_ADDRESS>;
+
 // Deoptimization
 def __llvm_deoptimize : RuntimeLibcallImpl<DEOPTIMIZE>;
 
diff --git a/llvm/lib/CodeGen/SafeStack.cpp b/llvm/lib/CodeGen/SafeStack.cpp
index a6c1a76f53f39..996207034d076 100644
--- a/llvm/lib/CodeGen/SafeStack.cpp
+++ b/llvm/lib/CodeGen/SafeStack.cpp
@@ -799,8 +799,16 @@ bool SafeStack::run() {
     IRB.SetCurrentDebugLocation(
         DILocation::get(SP->getContext(), SP->getScopeLine(), 0, SP));
   if (SafeStackUsePointerAddress) {
+    const char *SafestackPointerAddressName =
+        TL.getLibcallName(RTLIB::SAFESTACK_POINTER_ADDRESS);
+    if (!SafestackPointerAddressName) {
+      F.getContext().emitError(
+          "no libcall available for safestack pointer address");
+      return false;
+    }
+
     FunctionCallee Fn = F.getParent()->getOrInsertFunction(
-        "__safestack_pointer_address", IRB.getPtrTy(0));
+        SafestackPointerAddressName, IRB.getPtrTy(0));
     UnsafeStackPtr = IRB.CreateCall(Fn);
   } else {
     UnsafeStackPtr = TL.getSafeStackPointerLocation(IRB);
diff --git 
a/llvm/test/Transforms/SafeStack/NVPTX/safestack-pointer-address-libcall-error.ll
 
b/llvm/test/Transforms/SafeStack/NVPTX/safestack-pointer-address-libcall-error.ll
new file mode 100644
index 0000000000000..9bf84585e5468
--- /dev/null
+++ 
b/llvm/test/Transforms/SafeStack/NVPTX/safestack-pointer-address-libcall-error.ll
@@ -0,0 +1,12 @@
+; RUN: not opt -disable-output -mtriple=nvptx64-- 
-safestack-use-pointer-address -mcpu=sm_90 -passes=safe-stack %s 2>&1 | 
FileCheck %s
+
+; CHECK: error: no libcall available for safestack pointer address
+define void @foo(i32 %t) #0 {
+  %vla = alloca i32, i32 %t, align 4
+  call void @baz(ptr %vla)
+  ret void
+}
+
+declare void @baz(ptr)
+
+attributes #0 = { nounwind safestack sspstrong }

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