[llvm] [llvm::transforms] Add overflow check in AllocaInst::getAllocationSize (PR #97170)

[Thorsten Schütt via llvm-commits]

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@@ -60,22 +61,33 @@ static cl::opt<bool> DisableI2pP2iOpt(
 std::optional<TypeSize>
 AllocaInst::getAllocationSize(const DataLayout &DL) const {
   TypeSize Size = DL.getTypeAllocSize(getAllocatedType());
-  if (isArrayAllocation()) {
-    auto *C = dyn_cast<ConstantInt>(getArraySize());
-    if (!C)
-      return std::nullopt;
-    assert(!Size.isScalable() && "Array elements cannot have a scalable size");
-    Size *= C->getZExtValue();
+  if (!isArrayAllocation()) {
+    return Size;
   }
-  return Size;
+  auto *C = dyn_cast<ConstantInt>(getArraySize());
+  if (!C)
+    return std::nullopt;
+  assert(!Size.isScalable() && "Array elements cannot have a scalable size");
+  auto checkedProd =
+      checkedMulUnsigned(Size.getKnownMinValue(), C->getZExtValue());
+  if (!checkedProd) {
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tschuett wrote:

Please remove redundant braces.

https://github.com/llvm/llvm-project/pull/97170