Allow 128-bit discriminants in DWARF variants (#125578)

If a variant part has a 128-bit discriminator, then
DwarfUnit::constructTypeDIE will assert.  This patch fixes the problem
by allowing any size of integer to be used here.  This is largely
accomplished by moving part of DwarfUnit::addConstantValue to a new
method.

Fixes #119655

Author: tromey

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -232,6 +232,42 @@ void DwarfUnit::addUInt(DIEValueList &Block, dwarf::Form Form,
   addUInt(Block, (dwarf::Attribute)0, Form, Integer);
 }
 
+void DwarfUnit::addIntAsBlock(DIE &Die, dwarf::Attribute Attribute, const APInt &Val) {
+  DIEBlock *Block = new (DIEValueAllocator) DIEBlock;
+
+  // Get the raw data form of the large APInt.
+  const uint64_t *Ptr64 = Val.getRawData();
+
+  int NumBytes = Val.getBitWidth() / 8; // 8 bits per byte.
+  bool LittleEndian = Asm->getDataLayout().isLittleEndian();
+
+  // Output the constant to DWARF one byte at a time.
+  for (int i = 0; i < NumBytes; i++) {
+    uint8_t c;
+    if (LittleEndian)
+      c = Ptr64[i / 8] >> (8 * (i & 7));
+    else
+      c = Ptr64[(NumBytes - 1 - i) / 8] >> (8 * ((NumBytes - 1 - i) & 7));
+    addUInt(*Block, dwarf::DW_FORM_data1, c);
+  }
+
+  addBlock(Die, Attribute, Block);
+}
+
+void DwarfUnit::addInt(DIE &Die, dwarf::Attribute Attribute,
+		       const APInt &Val, bool Unsigned) {
+  unsigned CIBitWidth = Val.getBitWidth();
+  if (CIBitWidth <= 64) {
+    if (Unsigned)
+      addUInt(Die, Attribute, std::nullopt, Val.getZExtValue());
+    else
+      addSInt(Die, Attribute, std::nullopt, Val.getSExtValue());
+    return;
+  }
+
+  addIntAsBlock(Die, Attribute, Val);
+}
+
 void DwarfUnit::addSInt(DIEValueList &Die, dwarf::Attribute Attribute,
                         std::optional<dwarf::Form> Form, int64_t Integer) {
   if (!Form)
@@ -484,25 +520,7 @@ void DwarfUnit::addConstantValue(DIE &Die, const APInt &Val, bool Unsigned) {
     return;
   }
 
-  DIEBlock *Block = new (DIEValueAllocator) DIEBlock;
-
-  // Get the raw data form of the large APInt.
-  const uint64_t *Ptr64 = Val.getRawData();
-
-  int NumBytes = Val.getBitWidth() / 8; // 8 bits per byte.
-  bool LittleEndian = Asm->getDataLayout().isLittleEndian();
-
-  // Output the constant to DWARF one byte at a time.
-  for (int i = 0; i < NumBytes; i++) {
-    uint8_t c;
-    if (LittleEndian)
-      c = Ptr64[i / 8] >> (8 * (i & 7));
-    else
-      c = Ptr64[(NumBytes - 1 - i) / 8] >> (8 * ((NumBytes - 1 - i) & 7));
-    addUInt(*Block, dwarf::DW_FORM_data1, c);
-  }
-
-  addBlock(Die, dwarf::DW_AT_const_value, Block);
+  addIntAsBlock(Die, dwarf::DW_AT_const_value, Val);
 }
 
 void DwarfUnit::addLinkageName(DIE &Die, StringRef LinkageName) {
@@ -972,12 +990,8 @@ void DwarfUnit::constructTypeDIE(DIE &Buffer, const DICompositeType *CTy) {
           DIE &Variant = createAndAddDIE(dwarf::DW_TAG_variant, Buffer);
           if (const ConstantInt *CI =
               dyn_cast_or_null<ConstantInt>(DDTy->getDiscriminantValue())) {
-            if (DD->isUnsignedDIType(Discriminator->getBaseType()))
-              addUInt(Variant, dwarf::DW_AT_discr_value, std::nullopt,
-                      CI->getZExtValue());
-            else
-              addSInt(Variant, dwarf::DW_AT_discr_value, std::nullopt,
-                      CI->getSExtValue());
+	    addInt(Variant, dwarf::DW_AT_discr_value, CI->getValue(),
+		   DD->isUnsignedDIType(Discriminator->getBaseType()));
           }
           constructMemberDIE(Variant, DDTy);
         } else {

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h

@@ -167,6 +167,10 @@ class DwarfUnit : public DIEUnit {
 
   void addSInt(DIELoc &Die, std::optional<dwarf::Form> Form, int64_t Integer);
 
+  /// Add an integer attribute data and value; value may be any width.
+  void addInt(DIE &Die, dwarf::Attribute Attribute, const APInt &Integer,
+	      bool Unsigned);
+
   /// Add a string attribute data and value.
   ///
   /// We always emit a reference to the string pool instead of immediate
@@ -334,6 +338,10 @@ class DwarfUnit : public DIEUnit {
   void emitCommonHeader(bool UseOffsets, dwarf::UnitType UT);
 
 private:
+  /// A helper to add a wide integer constant to a DIE using a block
+  /// form.
+  void addIntAsBlock(DIE &Die, dwarf::Attribute Attribute, const APInt &Val);
+
   void constructTypeDIE(DIE &Buffer, const DIBasicType *BTy);
   void constructTypeDIE(DIE &Buffer, const DIStringType *BTy);
   void constructTypeDIE(DIE &Buffer, const DIDerivedType *DTy);

llvm/test/DebugInfo/Generic/discriminated-union.ll

@@ -22,7 +22,7 @@
 ;         CHECK: DW_AT_alignment
 ;         CHECK: DW_AT_data_member_location [DW_FORM_data1]	(0x00)
 ;     CHECK: DW_TAG_variant
-;       CHECK: DW_AT_discr_value [DW_FORM_data1]	(0x00)
+;       CHECK: DW_AT_discr_value [DW_FORM_block1]	(<0x10> 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 )
 ;       CHECK: DW_TAG_member
 ;         CHECK: DW_AT_type
 ;         CHECK: DW_AT_alignment
@@ -71,7 +71,7 @@ attributes #0 = { nounwind uwtable }
 !21 = !DIBasicType(name: "u8", size: 8, encoding: DW_ATE_unsigned)
 !22 = !DIDerivedType(tag: DW_TAG_member, name: "__1", scope: !18, file: !7, baseType: !23, size: 64, align: 64)
 !23 = !DIDerivedType(tag: DW_TAG_pointer_type, name: "&u8", baseType: !21, size: 64, align: 64)
-!24 = !DIDerivedType(tag: DW_TAG_member, scope: !14, file: !7, baseType: !25, size: 128, align: 64, extraData: i64 0)
+!24 = !DIDerivedType(tag: DW_TAG_member, scope: !14, file: !7, baseType: !25, size: 128, align: 64, extraData: i128 18446744073709551616)
 !25 = !DICompositeType(tag: DW_TAG_structure_type, name: "Nope", scope: !12, file: !7, size: 128, align: 64, elements: !4, identifier: "7ce1efff6b82281ab9ceb730566e7e20::Nope")
 !27 = !DIBasicType(name: "u64", size: 64, encoding: DW_ATE_unsigned)
 !28 = !DIExpression()