[Lldb-commits] [lldb] [lldb] Compare generic DWARF relational operands as signed values (PR #218335)
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lldb-commits at lists.llvm.org
Mon Aug 24 02:24:34 PDT 2026
https://github.com/MrEven132 updated https://github.com/llvm/llvm-project/pull/218335
>From ef38c25666f4294fd20008653431e551ee885d05 Mon Sep 17 00:00:00 2001
From: MrEven132 <13554966229 at 163.com>
Date: Mon, 24 Aug 2026 16:46:52 +0800
Subject: [PATCH 1/6] [lldb][NFC] Add generic operand comparison helpers
---
lldb/source/Expression/DWARFExpression.cpp | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 91c47546eeac7..72e6a5144a1e2 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -1380,6 +1380,12 @@ static llvm::Error CheckScalarOperandsHaveSameType(const Scalar &lhs,
return llvm::Error::success();
}
+static bool IsPotentiallyGenericIntegerOperand(const Scalar &operand,
+ size_t address_size) {
+ return address_size != 0 && operand.GetType() == Scalar::e_int &&
+ operand.GetByteSize() == address_size;
+}
+
llvm::Expected<Value> DWARFExpression::Evaluate(
ExecutionContext *exe_ctx, RegisterContext *reg_ctx,
lldb::ModuleSP module_sp, const DataExtractor &opcodes,
@@ -1419,6 +1425,14 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
!is_signed));
};
+ auto make_generic_operands_signed = [&](Scalar &lhs, Scalar &rhs) {
+ if (IsPotentiallyGenericIntegerOperand(lhs, address_size) &&
+ IsPotentiallyGenericIntegerOperand(rhs, address_size)) {
+ lhs.MakeSigned();
+ rhs.MakeSigned();
+ }
+ };
+
llvm::DWARFExpression::iterator op = expr.begin(), op_end = expr.end();
while (op != op_end) {
const uint64_t op_offset = op.getOffset();
>From 84cbe4cbcbde32368bb0a59f0e7599df1bd86f52 Mon Sep 17 00:00:00 2001
From: MrEven132 <13554966229 at 163.com>
Date: Mon, 24 Aug 2026 16:50:13 +0800
Subject: [PATCH 2/6] [lldb] Compare generic DW_OP_ge operands as signed
---
lldb/source/Expression/DWARFExpression.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 72e6a5144a1e2..98e1e77dfa5b1 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -1759,6 +1759,7 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
return err;
tmp = stack.back();
stack.pop_back();
+ make_generic_operands_signed(stack.back().GetScalar(), tmp.GetScalar());
stack.back().GetScalar() =
to_generic(stack.back().GetScalar() >= tmp.GetScalar());
break;
>From bac0255cf87a326e96189a9400f5620a6ddd63a1 Mon Sep 17 00:00:00 2001
From: MrEven132 <13554966229 at 163.com>
Date: Mon, 24 Aug 2026 16:50:40 +0800
Subject: [PATCH 3/6] [lldb] Compare generic DW_OP_gt operands as signed
---
lldb/source/Expression/DWARFExpression.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 98e1e77dfa5b1..1c0d3b2cb6676 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -1771,6 +1771,7 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
return err;
tmp = stack.back();
stack.pop_back();
+ make_generic_operands_signed(stack.back().GetScalar(), tmp.GetScalar());
stack.back().GetScalar() =
to_generic(stack.back().GetScalar() > tmp.GetScalar());
break;
>From 5598ad4fe90ff4dc7272d7a56867e517f7ae90a8 Mon Sep 17 00:00:00 2001
From: MrEven132 <13554966229 at 163.com>
Date: Mon, 24 Aug 2026 16:51:05 +0800
Subject: [PATCH 4/6] [lldb] Compare generic DW_OP_le operands as signed
---
lldb/source/Expression/DWARFExpression.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 1c0d3b2cb6676..e121f843291e1 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -1783,6 +1783,7 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
return err;
tmp = stack.back();
stack.pop_back();
+ make_generic_operands_signed(stack.back().GetScalar(), tmp.GetScalar());
stack.back().GetScalar() =
to_generic(stack.back().GetScalar() <= tmp.GetScalar());
break;
>From d6f01f0f805cd4d419c53665a6bc8611bf4a0cce Mon Sep 17 00:00:00 2001
From: MrEven132 <13554966229 at 163.com>
Date: Mon, 24 Aug 2026 16:52:16 +0800
Subject: [PATCH 5/6] [lldb] Compare generic DW_OP_lt operands as signed
---
lldb/source/Expression/DWARFExpression.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index e121f843291e1..a07bf5166ef51 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -1795,6 +1795,7 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
return err;
tmp = stack.back();
stack.pop_back();
+ make_generic_operands_signed(stack.back().GetScalar(), tmp.GetScalar());
stack.back().GetScalar() =
to_generic(stack.back().GetScalar() < tmp.GetScalar());
break;
>From 0d7ceb9c9d793093982649759b94eba1b684db88 Mon Sep 17 00:00:00 2001
From: MrEven132 <13554966229 at 163.com>
Date: Mon, 24 Aug 2026 17:23:51 +0800
Subject: [PATCH 6/6] [lldb] Test signed generic DWARF relational comparisons
Add regression coverage for DW_OP_lt, DW_OP_le, DW_OP_gt, and DW_OP_ge
using an address-sized all-one generic value compared with zero.
Assisted-by: Codex
---
.../Expression/DWARFExpressionTest.cpp | 39 +++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/lldb/unittests/Expression/DWARFExpressionTest.cpp b/lldb/unittests/Expression/DWARFExpressionTest.cpp
index 094cfaf790a9a..50bdc96be7c93 100644
--- a/lldb/unittests/Expression/DWARFExpressionTest.cpp
+++ b/lldb/unittests/Expression/DWARFExpressionTest.cpp
@@ -766,6 +766,45 @@ TEST(DWARFExpression, RelationalOpsProduceGenericResult) {
}
}
+TEST(DWARFExpression, GenericRelationalOpsUseSignedComparison) {
+ struct TestCase {
+ uint8_t opcode;
+ uint8_t expected;
+ };
+ constexpr TestCase test_cases[] = {
+ {DW_OP_lt, 1}, {DW_OP_le, 1}, {DW_OP_gt, 0}, {DW_OP_ge, 0}};
+
+ for (const TestCase &test : test_cases) {
+ // Generic relational operands are compared as signed values, so the
+ // unsigned encoding of all-one bits below represents -1 for comparison.
+ const std::vector<uint8_t> expr = {
+ DW_OP_const8u,
+ 0xff,
+ 0xff,
+ 0xff,
+ 0xff,
+ 0xff,
+ 0xff,
+ 0xff,
+ 0xff,
+ DW_OP_consts,
+ 0x00,
+ test.opcode,
+ DW_OP_stack_value,
+ };
+ DataExtractor extractor(expr.data(), expr.size(), lldb::eByteOrderLittle,
+ /*addr_size=*/8);
+
+ EXPECT_THAT_EXPECTED(
+ DWARFExpression::Evaluate(
+ /*exe_ctx=*/nullptr, /*reg_ctx=*/nullptr, /*module_sp=*/{},
+ extractor, /*unit=*/nullptr, lldb::eRegisterKindLLDB,
+ /*initial_value_ptr=*/nullptr, /*object_address_ptr=*/nullptr),
+ ExpectScalar(64, test.expected, false))
+ << "opcode 0x" << llvm::utohexstr(test.opcode);
+ }
+}
+
TEST(DWARFExpression, DW_OP_stack_value) {
EXPECT_THAT_EXPECTED(Evaluate({DW_OP_stack_value}), llvm::Failed());
}
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