[StackSafetyAnalysis] Bail out when calling ifunc

[MaskRay]

An assertion failure arises when a call instruction calls a GlobalIFunc.
Since we cannot reason about the underlying function, just bail out.

Fix #87923

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Fangrui Song (MaskRay)

Changes

An assertion failure arises when a call instruction calls a GlobalIFunc.
Since we cannot reason about the underlying function, just bail out.

Fix #87923

---

Full diff: https://github.com/llvm/llvm-project/pull/113841.diff

2 Files Affected:

• (modified) llvm/lib/Analysis/StackSafetyAnalysis.cpp (+1-1)
• (modified) llvm/test/Analysis/StackSafetyAnalysis/local.ll (+16)

diff --git a/llvm/lib/Analysis/StackSafetyAnalysis.cpp b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
index 27360d0e84cb2b..5d81658409dae8 100644
--- a/llvm/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
@@ -528,7 +528,7 @@ void StackSafetyLocalAnalysis::analyzeAllUses(Value *Ptr,
         // dso_preemptable aliases or aliases with interposable linkage.
         const GlobalValue *Callee =
             dyn_cast<GlobalValue>(CB.getCalledOperand()->stripPointerCasts());
-        if (!Callee) {
+        if (!Callee || isa<GlobalIFunc>(Callee)) {
           US.addRange(I, UnknownRange, /*IsSafe=*/false);
           break;
         }
diff --git a/llvm/test/Analysis/StackSafetyAnalysis/local.ll b/llvm/test/Analysis/StackSafetyAnalysis/local.ll
index 4a833611c78916..02d46c8449bae5 100644
--- a/llvm/test/Analysis/StackSafetyAnalysis/local.ll
+++ b/llvm/test/Analysis/StackSafetyAnalysis/local.ll
@@ -1120,5 +1120,21 @@ define void @NonPointer(ptr %p) {
   ret void
 }
 
+@ifunc = dso_local ifunc i64 (ptr), ptr @ifunc_resolver
+
+define dso_local void @CallIfunc(ptr noundef %uaddr) local_unnamed_addr {
+; CHECK-LABEL: @CallIfunc
+; CHECK-NEXT:  args uses:
+; CHECK-NEXT:    uaddr[]: full-set
+entry:
+  tail call i64 @ifunc(ptr noundef %uaddr)
+  ret void
+}
+
+define dso_local ptr @ifunc_resolver() {
+entry:
+  ret ptr null
+}
+
 declare void @llvm.lifetime.start.p0(i64, ptr nocapture)
 declare void @llvm.lifetime.end.p0(i64, ptr nocapture)

[DimitryAndric]

Yes, this works for me, both for the original test case, and for a full FreeBSD buildworld using WITH_ASAN.