[Clang] Prevent null pointer dereferences in SVE tuple functions

[smanna12]

This patch

addresses a null pointer dereference issue reported by static analyzer tool in the
EmitSVETupleSetOrGet() and EmitSVETupleCreate() functions. Previously, the function
assumed that the result of dyn_cast<> to ScalableVectorType would always be non-null,
which is not guaranteed.

The fix introduces a null check after the dyn_cast<> operation. If the cast fails and
SingleVecTy is null, the function now returns nullptr to indicate an error. This prevents the
dereference of a null pointer, which could lead to undefined behavior.

Additionally, the assert message has been corrected to accurately reflect the expected
conditions.

These changes collectively enhance the robustness of the code by ensuring type safety and preventing runtime errors due to improper type casting.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-codegen

Author: None (smanna12)

Changes

This patch replaces dyn_cast<> with cast<> for obtaining ScalableVectorType pointers in the EmitSVETupleSetOrGet() and EmitSVETupleCreate() functions to ensure that the code expects valid ScalableVectorType instances and will cause an assertion if the cast is invalid, preventing possible null pointer dereferences and improving codes safety.

---

Full diff: https://github.com/llvm/llvm-project/pull/94267.diff

1 Files Affected:

• (modified) clang/lib/CodeGen/CGBuiltin.cpp (+2-2)

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 37d0c478e0330..3ba9f4693170f 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -10211,7 +10211,7 @@ Value *CodeGenFunction::EmitSVETupleSetOrGet(const SVETypeFlags &TypeFlags,
          "Expects TypleFlag isTupleSet or TypeFlags.isTupleSet()");
 
   unsigned I = cast<ConstantInt>(Ops[1])->getSExtValue();
-  auto *SingleVecTy = dyn_cast<llvm::ScalableVectorType>(
+  auto *SingleVecTy = cast<llvm::ScalableVectorType>(
                       TypeFlags.isTupleSet() ? Ops[2]->getType() : Ty);
   Value *Idx = ConstantInt::get(CGM.Int64Ty,
                                 I * SingleVecTy->getMinNumElements());
@@ -10226,7 +10226,7 @@ Value *CodeGenFunction::EmitSVETupleCreate(const SVETypeFlags &TypeFlags,
                                              ArrayRef<Value *> Ops) {
   assert(TypeFlags.isTupleCreate() && "Expects TypleFlag isTupleCreate");
 
-  auto *SrcTy = dyn_cast<llvm::ScalableVectorType>(Ops[0]->getType());
+  auto *SrcTy = cast<llvm::ScalableVectorType>(Ops[0]->getType());
   unsigned MinElts = SrcTy->getMinNumElements();
   Value *Call = llvm::PoisonValue::get(Ty);
   for (unsigned I = 0; I < Ops.size(); I++) {

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[CarolineConcatto]

Thank you @smanna12.

[smanna12]

Thank you @CarolineConcatto for reviews!