[Lldb-commits] [lldb] [lldb] Zero extend APInt when piece size is bigger than the bitwidth (PR #150149)

[Pavel Labath via lldb-commits]

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@@ -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));
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labath wrote:

I think these two cases should be unified I don't see any reason why extension (or truncation) in DW_OP_piece should behave any differently from DW_OP_convert. And I don't like how this violates "campground rules" (leave the place in a better state than you found it in): instead of cleaning things up, it piles onto the existing dodgy implementation.

https://github.com/llvm/llvm-project/pull/150149