[CodeView] Encode signed int values correctly when emitting S_CONSTANTs

[rnk]

lgtm

llvm/test/DebugInfo/COFF/global-constants.ll

66

So, we actually already had a test for this, but didn't notice the mismatch during review. Oops. :)

[akhuang]

rebase

[akhuang]

I think we want to emit floats as unsigned, so add a function to check if the
constant is a float.

[rnk]

lgtm

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

for (const DIDerivedType *DTy : StaticConstMembers) {
     OS.emitBinaryData(SRef);
 
     OS.AddComment("Name");
     emitNullTerminatedSymbolName(OS, QualifiedName);
     endSymbolRecord(SConstantEnd);
   }
 }
 
+static bool isFloatDIType(const DIType *Ty) {
+  if (auto *CTy = dyn_cast<DICompositeType>(Ty))
+    return false;
+
+  if (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
+    dwarf::Tag T = (dwarf::Tag)Ty->getTag();
+    if (T == dwarf::DW_TAG_pointer_type ||
+        T == dwarf::DW_TAG_ptr_to_member_type ||
+        T == dwarf::DW_TAG_reference_type ||
+        T == dwarf::DW_TAG_rvalue_reference_type)
+      return false;
+    assert(DTy->getBaseType() && "Expected valid base type");
+    return isFloatDIType(DTy->getBaseType());
+  }
+
+  auto *BTy = cast<DIBasicType>(Ty);
+  return (BTy->getEncoding() == dwarf::DW_ATE_float);
+}
+
 void CodeViewDebug::emitDebugInfoForGlobal(const CVGlobalVariable &CVGV) {
   const DIGlobalVariable *DIGV = CVGV.DIGV;
 
   const DIScope *Scope = DIGV->getScope();
   // For static data members, get the scope from the declaration.
   if (const auto *MemberDecl = dyn_cast_or_null<DIDerivedType>(
           DIGV->getRawStaticDataMemberDeclaration()))
     Scope = MemberDecl->getScope();
if (const GlobalVariable *GV =
     OS.AddComment("Name");
     const unsigned LengthOfDataRecord = 12;
     emitNullTerminatedSymbolName(OS, QualifiedName, LengthOfDataRecord);
     endSymbolRecord(DataEnd);
   } else {
     const DIExpression *DIE = CVGV.GVInfo.get<const DIExpression *>();
     assert(DIE->isConstant() &&
            "Global constant variables must contain a constant expression.");
-    uint64_t Val = DIE->getElement(1);
+
+    // Use unsigned for floats.
+    bool isUnsigned = isFloatDIType(DIGV->getType())
+                          ? true
+                          : DebugHandlerBase::isUnsignedDIType(DIGV->getType());
+    APSInt Value(APInt(/*BitWidth=*/64, DIE->getElement(1)), isUnsigned);
 
     MCSymbol *SConstantEnd = beginSymbolRecord(SymbolKind::S_CONSTANT);
     OS.AddComment("Type");
     OS.emitInt32(getTypeIndex(DIGV->getType()).getIndex());
     OS.AddComment("Value");
 
     // Encoded integers shouldn't need more than 10 bytes.
     uint8_t data[10];
     BinaryStreamWriter Writer(data, llvm::support::endianness::little);
     CodeViewRecordIO IO(Writer);
-    cantFail(IO.mapEncodedInteger(Val));
+    cantFail(IO.mapEncodedInteger(Value));
     StringRef SRef((char *)data, Writer.getOffset());
     OS.emitBinaryData(SRef);
 
     OS.AddComment("Name");
     emitNullTerminatedSymbolName(OS, QualifiedName);
     endSymbolRecord(SConstantEnd);
   }
 }

llvm/test/DebugInfo/COFF/global-constants.ll

 ; ASM-NEXT:   .long 4099                    # Type
 ; ASM-NEXT:   .byte 0x04, 0x80, 0xc3, 0xf5  # Value
 ; ASM-NEXT:   .byte 0x48, 0x40
 ; ASM-NEXT:   .asciz  "Test1::TestConst1"     # Name
 ; ASM-NEXT:   .p2align  2
 
 ; ASM:        .short  4359                    # Record kind: S_CONSTANT
 ; ASM-NEXT:   .long 4101                    # Type
-; ASM-NEXT:   .byte 0x0a, 0x80, 0x40, 0x61  # Value
-; ASM-NEXT:   .byte 0x07, 0x80, 0xff, 0xff
-; ASM-NEXT:   .byte 0xff, 0xff
+; ASM-NEXT:   .byte 0x03, 0x80, 0x40, 0x61  # Value
+; ASM-NEXT:   .byte 0x07, 0x80
 ; ASM-NEXT:   .asciz  "ENUM_B"                # Name
 ; ASM-NEXT:   .p2align  2
 ; ASM-NOT:    .asciz "S::SEnum"             # Name
 
 ; ASM:        .short  4359                    # Record kind: S_CONSTANT
 ; ASM-NEXT:   .long 4105                    # Type
 ; ASM-NEXT:   .byte 0x00, 0x80, 0xf6        # Value
 ; ASM-NEXT:   .asciz  "S::TestConst2"         # Name
 ; ASM-NEXT:   .p2align  2
 
 ; OBJ:        CodeViewDebugInfo [
 ; OBJ:          Section: .debug$S
 ; OBJ:          Magic: 0x4
 ; OBJ:          Subsection [
 ; OBJ:            SubSectionType: Symbols (0xF1)
 ; OBJ:            ConstantSym {
 ; OBJ-NEXT:         Kind: S_CONSTANT (0x1107)
 ; OBJ-NEXT:         Type: const float (0x1003)
 ; OBJ-NEXT:         Value: 1078523331
 ; OBJ-NEXT:         Name: Test1::TestConst1
 ; OBJ-NEXT:       }
 ; OBJ-NEXT:       ConstantSym {
 ; OBJ-NEXT:         Kind: S_CONSTANT (0x1107)
 ; OBJ-NEXT:         Type: TestEnum (0x1005)
-; OBJ-NEXT:         Value: 18446744071562551616
+; OBJ-NEXT:         Value: -214700000
 ; OBJ-NEXT:         Name: ENUM_B
 ; OBJ-NEXT:       }
 ; OBJ-NOT:          Name: S::SEnum
 ; OBJ-NEXT:       ConstantSym {
 ; OBJ-NEXT:         Kind: S_CONSTANT (0x1107)
 ; OBJ-NEXT:         Type: const int (0x1009)
 ; OBJ-NEXT:         Value: -10
 ; OBJ-NEXT:         Name: S::TestConst2

llvm/test/DebugInfo/COFF/globals.ll

 ; ASM-NEXT:   .long   116                     # Type
 ; ASM-NEXT:   .secrel32       "?last@@3HA"    # DataOffset
 ; ASM-NEXT:   .secidx "?last@@3HA"            # Segment
 ; ASM-NEXT:   .asciz  "last"                  # Name
 ; ASM-NEXT:   .p2align        2
 
 ; ASM:        .short  4359                    # Record kind: S_CONSTANT
 ; ASM-NEXT:   .long 4100                    # Type
-; ASM-NEXT:   .byte 0x08, 0x00              # Value
+; ASM-NEXT:   .byte 0x00, 0x80, 0x08        # Value
 ; ASM-NEXT:   .asciz  "foo::constExpr"        # Name
 ; ASM-NEXT:   .p2align  2
 
 ; ASM:        .short  4359                    # Record kind: S_CONSTANT
 ; ASM-NEXT:   .long 4100                    # Type
-; ASM-NEXT:   .byte 0x09, 0x00              # Value
+; ASM-NEXT:   .byte 0x00, 0x80, 0x09        # Value
 ; ASM-NEXT:   .asciz  "foo::constVal"         # Name
 ; ASM-NEXT:   .p2align  2
 
 ; ASM:        .short  4359                    # Record kind: S_CONSTANT
 ; ASM-NEXT:   .long 4100                    # Type
-; ASM-NEXT:   .byte 0x0e, 0x00              # Value
+; ASM-NEXT:   .byte 0x00, 0x80, 0x0e        # Value
 ; ASM-NEXT:   .asciz  "foo::Data::DataConstExpr" # Name
 ; ASM-NEXT:   .p2align  2
 
 ; ASM:        .short  4364                    # Record kind: S_LDATA32
 ; ASM-NEXT:   .long   116                     # Type
 ; ASM-NEXT:   .secrel32       "?globalStatic@foo@@3HA" # DataOffset
 ; ASM-NEXT:   .secidx "?globalStatic@foo@@3HA" # Segment
 ; ASM-NEXT:   .asciz  "foo::globalStatic"     # Name