[llvm] [ADT] Fix an empty BitVector call getData assert `idx < size()' failed (PR #65505)

[via llvm-commits]

https://github.com/wingrez updated https://github.com/llvm/llvm-project/pull/65505:

>From 503a7542d52fa4b47f7c9e04dd78a7587ad04222 Mon Sep 17 00:00:00 2001
From: wingrez <wingrez at 126.com>
Date: Thu, 7 Sep 2023 01:21:00 +0800
Subject: [PATCH] [ADT] Fix an empty BitVector call getData assert `idx <
 size()' failed

Make sure calling getData() is legal even on an empty BitVector.
---
 llvm/include/llvm/ADT/BitVector.h    | 2 +-
 llvm/unittests/ADT/BitVectorTest.cpp | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/llvm/include/llvm/ADT/BitVector.h b/llvm/include/llvm/ADT/BitVector.h
index a8847a32675378..e0de1afcc94182 100644
--- a/llvm/include/llvm/ADT/BitVector.h
+++ b/llvm/include/llvm/ADT/BitVector.h
@@ -688,7 +688,7 @@ class BitVector {
   }
   bool isInvalid() const { return Size == (unsigned)-1; }
 
-  ArrayRef<BitWord> getData() const { return {&Bits[0], Bits.size()}; }
+  ArrayRef<BitWord> getData() const { return {Bits.data(), Bits.size()}; }
 
   //===--------------------------------------------------------------------===//
   // Portable bit mask operations.
diff --git a/llvm/unittests/ADT/BitVectorTest.cpp b/llvm/unittests/ADT/BitVectorTest.cpp
index ce043d47b97f1a..e00e11e4655aa0 100644
--- a/llvm/unittests/ADT/BitVectorTest.cpp
+++ b/llvm/unittests/ADT/BitVectorTest.cpp
@@ -1134,6 +1134,14 @@ TYPED_TEST(BitVectorTest, EmptyVector) {
   testEmpty(E);
 }
 
+/// Make sure calling getData() is legal even on an empty BitVector
+TYPED_TEST(BitVectorTest, EmptyVectorGetData) {
+  BitVector A;
+  testEmpty(A);
+  auto B = A.getData();
+  EXPECT_TRUE(B.empty());
+}
+
 TYPED_TEST(BitVectorTest, Iterators) {
   TypeParam Filled(10, true);
   EXPECT_NE(Filled.set_bits_begin(), Filled.set_bits_end());