DWARFFormValue: Add getAsSignedConstant method.

The implementation accepts explicitely signed forms (DW_FORM_sdata),
but also unsigned forms as long as they fit in an int64_t.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231299 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DebugInfo/DWARF/DWARFFormValue.h

@@ -74,6 +74,7 @@ public:
   /// DWARFFormValue has form class is suitable for representing Foo.
   Optional<uint64_t> getAsReference(const DWARFUnit *U) const;
   Optional<uint64_t> getAsUnsignedConstant() const;
+  Optional<int64_t> getAsSignedConstant() const;
   Optional<const char *> getAsCString(const DWARFUnit *U) const;
   Optional<uint64_t> getAsAddress(const DWARFUnit *U) const;
   Optional<uint64_t> getAsSectionOffset() const;

lib/DebugInfo/DWARF/DWARFFormValue.cpp

@@ -18,6 +18,7 @@
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
+#include <climits>
 using namespace llvm;
 using namespace dwarf;
 using namespace syntax;
@@ -557,6 +558,24 @@ Optional<uint64_t> DWARFFormValue::getAsUnsignedConstant() const {
   return Value.uval;
 }
 
+Optional<int64_t> DWARFFormValue::getAsSignedConstant() const {
+  if ((!isFormClass(FC_Constant) && !isFormClass(FC_Flag)) ||
+      (Form == DW_FORM_udata && uint64_t(LLONG_MAX) < Value.uval))
+    return None;
+  switch (Form) {
+  case DW_FORM_data4:
+    return int32_t(Value.uval);
+  case DW_FORM_data2:
+    return int16_t(Value.uval);
+  case DW_FORM_data1:
+    return int8_t(Value.uval);
+  case DW_FORM_sdata:
+  case DW_FORM_data8:
+  default:
+    return Value.sval;
+  }
+}
+
 Optional<ArrayRef<uint8_t>> DWARFFormValue::getAsBlock() const {
   if (!isFormClass(FC_Block) && !isFormClass(FC_Exprloc))
     return None;

unittests/DebugInfo/DWARF/DWARFFormValueTest.cpp

@@ -8,7 +8,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/Support/Dwarf.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/Host.h"
 #include "gtest/gtest.h"
 using namespace llvm;
 using namespace dwarf;
@@ -46,4 +49,75 @@ TEST(DWARFFormValue, FormClass) {
   EXPECT_TRUE(isFormClass(DW_FORM_ref_sig8, DWARFFormValue::FC_Reference));
 }
 
+template<typename RawTypeT>
+DWARFFormValue createDataXFormValue(uint16_t Form, RawTypeT Value) {
+  char Raw[sizeof(RawTypeT)];
+  memcpy(Raw, &Value, sizeof(RawTypeT));
+  uint32_t Offset = 0;
+  DWARFFormValue Result(Form);
+  DataExtractor Data(StringRef(Raw, sizeof(RawTypeT)),
+                     sys::IsLittleEndianHost, sizeof(void*));
+  Result.extractValue(Data, &Offset, nullptr);
+  return Result;
+}
+
+DWARFFormValue createULEBFormValue(uint64_t Value) {
+  SmallString<10> RawData;
+  raw_svector_ostream OS(RawData);
+  encodeULEB128(Value, OS);
+  uint32_t Offset = 0;
+  DWARFFormValue Result(DW_FORM_udata);
+  DataExtractor Data(OS.str(), sys::IsLittleEndianHost, sizeof(void*));
+  Result.extractValue(Data, &Offset, nullptr);
+  return Result;
+}
+
+DWARFFormValue createSLEBFormValue(int64_t Value) {
+  SmallString<10> RawData;
+  raw_svector_ostream OS(RawData);
+  encodeSLEB128(Value, OS);
+  uint32_t Offset = 0;
+  DWARFFormValue Result(DW_FORM_sdata);
+  DataExtractor Data(OS.str(), sys::IsLittleEndianHost, sizeof(void*));
+  Result.extractValue(Data, &Offset, nullptr);
+  return Result;
+}
+
+TEST(DWARFFormValue, SignedConstantForms) {
+  // Check that we correctly sign extend fixed size forms.
+  auto Sign1 = createDataXFormValue<uint8_t>(DW_FORM_data1, -123);
+  auto Sign2 = createDataXFormValue<uint16_t>(DW_FORM_data2, -12345);
+  auto Sign4 = createDataXFormValue<uint32_t>(DW_FORM_data4, -123456789);
+  auto Sign8 = createDataXFormValue<uint64_t>(DW_FORM_data8, -1);
+  EXPECT_EQ(Sign1.getAsSignedConstant().getValue(), -123);
+  EXPECT_EQ(Sign2.getAsSignedConstant().getValue(), -12345);
+  EXPECT_EQ(Sign4.getAsSignedConstant().getValue(), -123456789);
+  EXPECT_EQ(Sign8.getAsSignedConstant().getValue(), -1);
+
+  // Check that we can handle big positive values, but that we return
+  // an error just over the limit.
+  auto UMax = createULEBFormValue(LLONG_MAX);
+  auto TooBig = createULEBFormValue(LLONG_MAX + 1);
+  EXPECT_EQ(UMax.getAsSignedConstant().getValue(), LLONG_MAX);
+  EXPECT_EQ(TooBig.getAsSignedConstant().hasValue(), false);
+
+  // Sanity check some other forms.
+  auto Data1 = createDataXFormValue<uint8_t>(DW_FORM_data1, 120);
+  auto Data2 = createDataXFormValue<uint16_t>(DW_FORM_data2, 32000);
+  auto Data4 = createDataXFormValue<uint32_t>(DW_FORM_data4, 2000000000);
+  auto Data8 = createDataXFormValue<uint64_t>(DW_FORM_data8, 0x1234567812345678LL);
+  auto LEBMin = createSLEBFormValue(LLONG_MIN);
+  auto LEBMax = createSLEBFormValue(LLONG_MAX);
+  auto LEB1 = createSLEBFormValue(-42);
+  auto LEB2 = createSLEBFormValue(42);
+  EXPECT_EQ(Data1.getAsSignedConstant().getValue(), 120);
+  EXPECT_EQ(Data2.getAsSignedConstant().getValue(), 32000);
+  EXPECT_EQ(Data4.getAsSignedConstant().getValue(), 2000000000);
+  EXPECT_EQ(Data8.getAsSignedConstant().getValue(), 0x1234567812345678LL);
+  EXPECT_EQ(LEBMin.getAsSignedConstant().getValue(), LLONG_MIN);
+  EXPECT_EQ(LEBMax.getAsSignedConstant().getValue(), LLONG_MAX);
+  EXPECT_EQ(LEB1.getAsSignedConstant().getValue(), -42);
+  EXPECT_EQ(LEB2.getAsSignedConstant().getValue(), 42);
+}
+
 } // end anonymous namespace