Zero extend APInt when piece size is bigger than the bitwidth

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Differential Revision: https://phabricator.intern.facebook.com/D78791142

Author: satyajanga

lldb/source/Expression/DWARFExpression.cpp

@@ -1978,7 +1978,12 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
             // grows to the nearest host integer type.
             llvm::APInt fail_value(1, 0, false);
             llvm::APInt ap_int = scalar.UInt128(fail_value);
-            assert(ap_int.getBitWidth() >= bit_size);
+            // We have seen a case where we have expression like:
+            //      DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x28
+            // here we are assuming the compiler was trying to zero
+            // extend the value that we should append to the buffer.
+            if (ap_int.getBitWidth() < bit_size)
+              ap_int = ap_int.zext(bit_size);
             llvm::ArrayRef<uint64_t> buf{ap_int.getRawData(),
                                          ap_int.getNumWords()};
             curr_piece.GetScalar() = Scalar(llvm::APInt(bit_size, buf));

lldb/unittests/Expression/DWARFExpressionTest.cpp

@@ -358,6 +358,26 @@ TEST(DWARFExpression, DW_OP_piece) {
       llvm::HasValue(GetScalar(16, 0xff00, true)));
 }
 
+TEST(DWARFExpression, DW_OP_piece_host_address) {
+  llvm::ArrayRef<uint8_t> expr = {DW_OP_lit2, DW_OP_stack_value, DW_OP_piece,
+                                  40};
+  DataExtractor extractor(expr.data(), expr.size(), lldb::eByteOrderLittle, 4);
+
+  // This tests if ap_int is extended to the right width.
+  // expect 40*8 = 320 bits size.
+  llvm::Expected<Value> result =
+      DWARFExpression::Evaluate(nullptr, nullptr, nullptr, extractor, nullptr,
+                                lldb::eRegisterKindLLDB, nullptr, nullptr);
+  ASSERT_THAT_EXPECTED(result, llvm::Succeeded());
+  ASSERT_EQ(result->GetValueType(), Value::ValueType::HostAddress);
+  ASSERT_EQ(result->GetBuffer().GetByteSize(), 40);
+  const uint8_t *data = result->GetBuffer().GetBytes();
+  ASSERT_EQ(data[0], 2);
+  for (int i = 1; i < 40; i++) {
+    ASSERT_EQ(data[i], 0);
+  }
+}
+
 TEST(DWARFExpression, DW_OP_implicit_value) {
   unsigned char bytes = 4;