[DebugInfo] Add num_extra_inhabitants to debug info (#112590)

An extra inhabitant is a bit pattern that does not represent a valid
value for instances of a given type. The number of extra inhabitants is
the number of those bit configurations.

This is used by Swift to save space when composing types. For example,
because Bool only needs 2 bit patterns to represent all of its values
(true and false), an Optional<Bool> only occupies 1 byte in memory by
using a bit configuration that is unused by Bool. Which bit patterns are
unused are part of the ABI of the language.

Since Swift generics are not monomorphized, by using dynamic libraries
you can have generic types whose size, alignment, etc, are known only
at runtime (which is why this feature is needed).

This patch adds num_extra_inhabitants to LLVM-IR debug info and in DWARF
as an Apple extension.

1 files changed, 28 insertions, 25 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index fb4326e..f7268a5 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -663,14 +663,16 @@ DIEnumerator *DIEnumerator::getImpl(LLVMContext &Context, const APInt &Value,
 DIBasicType *DIBasicType::getImpl(LLVMContext &Context, unsigned Tag,
                                   MDString *Name, uint64_t SizeInBits,
                                   uint32_t AlignInBits, unsigned Encoding,
-                                  DIFlags Flags, StorageType Storage,
-                                  bool ShouldCreate) {
+                                  uint32_t NumExtraInhabitants, DIFlags Flags,
+                                  StorageType Storage, bool ShouldCreate) {
   assert(isCanonical(Name) && "Expected canonical MDString");
-  DEFINE_GETIMPL_LOOKUP(DIBasicType,
-                        (Tag, Name, SizeInBits, AlignInBits, Encoding, Flags));
+  DEFINE_GETIMPL_LOOKUP(DIBasicType, (Tag, Name, SizeInBits, AlignInBits,
+                                      Encoding, NumExtraInhabitants, Flags));
   Metadata *Ops[] = {nullptr, nullptr, Name};
-  DEFINE_GETIMPL_STORE(DIBasicType,
-                       (Tag, SizeInBits, AlignInBits, Encoding, Flags), Ops);
+  DEFINE_GETIMPL_STORE(
+      DIBasicType,
+      (Tag, SizeInBits, AlignInBits, Encoding, NumExtraInhabitants, Flags),
+      Ops);
 }
 
 std::optional<DIBasicType::Signedness> DIBasicType::getSignedness() const {
@@ -768,8 +770,8 @@ DICompositeType *DICompositeType::getImpl(
     Metadata *Elements, unsigned RuntimeLang, Metadata *VTableHolder,
     Metadata *TemplateParams, MDString *Identifier, Metadata *Discriminator,
     Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
-    Metadata *Rank, Metadata *Annotations, StorageType Storage,
-    bool ShouldCreate) {
+    Metadata *Rank, Metadata *Annotations, uint32_t NumExtraInhabitants,
+    StorageType Storage, bool ShouldCreate) {
   assert(isCanonical(Name) && "Expected canonical MDString");
 
   // Keep this in sync with buildODRType.
@@ -778,25 +780,25 @@ DICompositeType *DICompositeType::getImpl(
                          AlignInBits, OffsetInBits, Flags, Elements,
                          RuntimeLang, VTableHolder, TemplateParams, Identifier,
                          Discriminator, DataLocation, Associated, Allocated,
-                         Rank, Annotations));
+                         Rank, Annotations, NumExtraInhabitants));
   Metadata *Ops[] = {File,          Scope,        Name,           BaseType,
                      Elements,      VTableHolder, TemplateParams, Identifier,
                      Discriminator, DataLocation, Associated,     Allocated,
                      Rank,          Annotations};
-  DEFINE_GETIMPL_STORE(
-      DICompositeType,
-      (Tag, Line, RuntimeLang, SizeInBits, AlignInBits, OffsetInBits, Flags),
-      Ops);
+  DEFINE_GETIMPL_STORE(DICompositeType,
+                       (Tag, Line, RuntimeLang, SizeInBits, AlignInBits,
+                        OffsetInBits, NumExtraInhabitants, Flags),
+                       Ops);
 }
 
 DICompositeType *DICompositeType::buildODRType(
     LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
     Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,
     uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
-    DIFlags Flags, Metadata *Elements, unsigned RuntimeLang,
-    Metadata *VTableHolder, Metadata *TemplateParams, Metadata *Discriminator,
-    Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
-    Metadata *Rank, Metadata *Annotations) {
+    uint32_t NumExtraInhabitants, DIFlags Flags, Metadata *Elements,
+    unsigned RuntimeLang, Metadata *VTableHolder, Metadata *TemplateParams,
+    Metadata *Discriminator, Metadata *DataLocation, Metadata *Associated,
+    Metadata *Allocated, Metadata *Rank, Metadata *Annotations) {
   assert(!Identifier.getString().empty() && "Expected valid identifier");
   if (!Context.isODRUniquingDebugTypes())
     return nullptr;
@@ -806,7 +808,8 @@ DICompositeType *DICompositeType::buildODRType(
                Context, Tag, Name, File, Line, Scope, BaseType, SizeInBits,
                AlignInBits, OffsetInBits, Flags, Elements, RuntimeLang,
                VTableHolder, TemplateParams, &Identifier, Discriminator,
-               DataLocation, Associated, Allocated, Rank, Annotations);
+               DataLocation, Associated, Allocated, Rank, Annotations,
+               NumExtraInhabitants);
 
   if (CT->getTag() != Tag)
     return nullptr;
@@ -818,7 +821,7 @@ DICompositeType *DICompositeType::buildODRType(
 
   // Mutate CT in place.  Keep this in sync with getImpl.
   CT->mutate(Tag, Line, RuntimeLang, SizeInBits, AlignInBits, OffsetInBits,
-             Flags);
+             NumExtraInhabitants, Flags);
   Metadata *Ops[] = {File,          Scope,        Name,           BaseType,
                      Elements,      VTableHolder, TemplateParams, &Identifier,
                      Discriminator, DataLocation, Associated,     Allocated,
@@ -835,10 +838,10 @@ DICompositeType *DICompositeType::getODRType(
     LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
     Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,
     uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
-    DIFlags Flags, Metadata *Elements, unsigned RuntimeLang,
-    Metadata *VTableHolder, Metadata *TemplateParams, Metadata *Discriminator,
-    Metadata *DataLocation, Metadata *Associated, Metadata *Allocated,
-    Metadata *Rank, Metadata *Annotations) {
+    uint32_t NumExtraInhabitants, DIFlags Flags, Metadata *Elements,
+    unsigned RuntimeLang, Metadata *VTableHolder, Metadata *TemplateParams,
+    Metadata *Discriminator, Metadata *DataLocation, Metadata *Associated,
+    Metadata *Allocated, Metadata *Rank, Metadata *Annotations) {
   assert(!Identifier.getString().empty() && "Expected valid identifier");
   if (!Context.isODRUniquingDebugTypes())
     return nullptr;
@@ -848,7 +851,7 @@ DICompositeType *DICompositeType::getODRType(
         Context, Tag, Name, File, Line, Scope, BaseType, SizeInBits,
         AlignInBits, OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder,
         TemplateParams, &Identifier, Discriminator, DataLocation, Associated,
-        Allocated, Rank, Annotations);
+        Allocated, Rank, Annotations, NumExtraInhabitants);
   } else {
     if (CT->getTag() != Tag)
       return nullptr;
@@ -867,7 +870,7 @@ DISubroutineType::DISubroutineType(LLVMContext &C, StorageType Storage,
                                    DIFlags Flags, uint8_t CC,
                                    ArrayRef<Metadata *> Ops)
     : DIType(C, DISubroutineTypeKind, Storage, dwarf::DW_TAG_subroutine_type, 0,
-             0, 0, 0, Flags, Ops),
+             0, 0, 0, 0, Flags, Ops),
       CC(CC) {}
 
 DISubroutineType *DISubroutineType::getImpl(LLVMContext &Context, DIFlags Flags,