[llvm] CodeGen: Fix crash when no libcall is available for stackguard (PR #164211)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/164211

Not all the paths appear to be implemented for GlobalISel

>From 249f14a4cb4831727ee74d5d1f3564a6b7900091 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Thu, 16 Oct 2025 14:57:43 +0900
Subject: [PATCH] CodeGen: Fix crash when no libcall is available for
 stackguard

Not all the paths appear to be implemented for GlobalISel
---
 llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp  | 12 ++++++----
 .../SelectionDAG/SelectionDAGBuilder.cpp      | 23 ++++++++++++++-----
 llvm/test/CodeGen/AMDGPU/stackguard.ll        | 14 +++++++++++
 3 files changed, 39 insertions(+), 10 deletions(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/stackguard.ll

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 884c3f1692e94..ec2371d17c088 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -1862,15 +1862,19 @@ bool IRTranslator::translateVectorDeinterleave2Intrinsic(
 
 void IRTranslator::getStackGuard(Register DstReg,
                                  MachineIRBuilder &MIRBuilder) {
+  Value *Global = TLI->getSDagStackGuard(*MF->getFunction().getParent());
+  if (!Global) {
+    LLVMContext &Ctx = MIRBuilder.getContext();
+    Ctx.diagnose(DiagnosticInfoGeneric("unable to lower stackguard"));
+    MIRBuilder.buildUndef(DstReg);
+    return;
+  }
+
   const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
   MRI->setRegClass(DstReg, TRI->getPointerRegClass());
   auto MIB =
       MIRBuilder.buildInstr(TargetOpcode::LOAD_STACK_GUARD, {DstReg}, {});
 
-  Value *Global = TLI->getSDagStackGuard(*MF->getFunction().getParent());
-  if (!Global)
-    return;
-
   unsigned AddrSpace = Global->getType()->getPointerAddressSpace();
   LLT PtrTy = LLT::pointer(AddrSpace, DL->getPointerSizeInBits(AddrSpace));
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index cb0038c54f8c7..f9ff981981ee4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3126,12 +3126,16 @@ void SelectionDAGBuilder::visitSPDescriptorParent(StackProtectorDescriptor &SPD,
   if (TLI.useLoadStackGuardNode(M)) {
     Guard = getLoadStackGuard(DAG, dl, Chain);
   } else {
-    const Value *IRGuard = TLI.getSDagStackGuard(M);
-    SDValue GuardPtr = getValue(IRGuard);
-
-    Guard = DAG.getLoad(PtrMemTy, dl, Chain, GuardPtr,
-                        MachinePointerInfo(IRGuard, 0), Align,
-                        MachineMemOperand::MOVolatile);
+    if (const Value *IRGuard = TLI.getSDagStackGuard(M)) {
+      SDValue GuardPtr = getValue(IRGuard);
+      Guard = DAG.getLoad(PtrMemTy, dl, Chain, GuardPtr,
+                          MachinePointerInfo(IRGuard, 0), Align,
+                          MachineMemOperand::MOVolatile);
+    } else {
+      LLVMContext &Ctx = *DAG.getContext();
+      Ctx.diagnose(DiagnosticInfoGeneric("unable to lower stackguard"));
+      Guard = DAG.getPOISON(PtrMemTy);
+    }
   }
 
   // Perform the comparison via a getsetcc.
@@ -7361,6 +7365,13 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
       Res = DAG.getPtrExtOrTrunc(Res, sdl, PtrTy);
     } else {
       const Value *Global = TLI.getSDagStackGuard(M);
+      if (!Global) {
+        LLVMContext &Ctx = *DAG.getContext();
+        Ctx.diagnose(DiagnosticInfoGeneric("unable to lower stackguard"));
+        setValue(&I, DAG.getPOISON(PtrTy));
+        return;
+      }
+
       Align Align = DAG.getDataLayout().getPrefTypeAlign(Global->getType());
       Res = DAG.getLoad(PtrTy, sdl, Chain, getValue(Global),
                         MachinePointerInfo(Global, 0), Align,
diff --git a/llvm/test/CodeGen/AMDGPU/stackguard.ll b/llvm/test/CodeGen/AMDGPU/stackguard.ll
new file mode 100644
index 0000000000000..393686f86ac40
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/stackguard.ll
@@ -0,0 +1,14 @@
+; RUN: not llc -global-isel=0 -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 -filetype=null %s 2>&1 | FileCheck %s
+; RUN: not llc -global-isel -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 -filetype=null %s 2>&1 | FileCheck %s
+
+; FIXME: To actually support stackguard, need to fix intrinsic to
+; return pointer in any address space.
+
+; CHECK: error: unable to lower stackguard
+define i1 @test_stackguard(ptr %p1) {
+  %p2 = call ptr @llvm.stackguard()
+  %res = icmp ne ptr %p2, %p1
+  ret i1 %res
+}
+
+declare ptr @llvm.stackguard()