[bindings/go] Add debug information accessors

[aykevl]

Summary

Add debug information accessors, as provided in the following patches:

https://reviews.llvm.org/D46627 (DILocation)
https://reviews.llvm.org/D52693 metadata kind
https://reviews.llvm.org/D60481 get/set debug location on a Value
https://reviews.llvm.org/D60489 (DIScope)

If needed I can split this patch up in multiple pieces if that's easier to review. But this is the subset that is required to read debug information from the IR so it makes testing locally easier.

The API as proposed in this patch is similar to the current Value API, with a single root type and methods that are only valid for certain subclasses. I have considered just implementing generic Line() calls (that are valid on all DINodes that have a line) but the implementation of that got a bit awkward without support from the C API. I've also considered creating generic getters like a Metadata.DebugLoc() that returns a DebugLoc, but there is a mismatch between the Go DI nodes in the LLVM API and the actual DINode class hierarchy, so that's also hard to get right (without being confusing or breaking the API).

[aykevl]

bindings/go/llvm/dibuilder.go

657

FileFilename is a bit weird but I used it (instead of just Filename for example) for consistency with the other getters.

[CodaFi]

LGTM.

We spoke out of band about the troubles I’m having verifying this locally, but the patch looks good and my limitations shouldn’t hold it back any longer.

@echristo is the Go authority IIRC.

[echristo]

*points at pcc* :)

[aykevl]

@CodaFi thanks for the review! I assume "Accepted" means it can be merged now? (Just checking to be sure).

---

Unfortunately, it looks like @pcc isn't maintaining the Go bindings anymore. He isn't listed as code owner of the Go bindings but is listed as the code owner of llgo which is the closest I could find.
I am willing to take over code ownership of the Go bindings, at least for now, simply because it looks like I'm using them the most lately. I'm not sure what the procedure or required trust level of such a thing would be but proposing it now anyway :)

bindings/go/llvm/dibuilder.go

func (c Context) TemporaryMDNode(mds []Metadata) (md Metadata) {
   ptr, nvals := llvmMetadataRefs(mds)
   md.C = C.LLVMTemporaryMDNode(c.C, ptr, C.size_t(nvals))
   return
 }
 
 func (md Metadata) ReplaceAllUsesWith(new Metadata) {
   C.LLVMMetadataReplaceAllUsesWith(md.C, new.C)
 }
+
+type MetadataKind C.LLVMMetadataKind
+
+const (
+  MDStringMetadataKind                     = C.LLVMMDStringMetadataKind
+  ConstantAsMetadataMetadataKind           = C.LLVMConstantAsMetadataMetadataKind
+  LocalAsMetadataMetadataKind              = C.LLVMLocalAsMetadataMetadataKind
+  DistinctMDOperandPlaceholderMetadataKind = C.LLVMDistinctMDOperandPlaceholderMetadataKind
+  MDTupleMetadataKind                      = C.LLVMMDTupleMetadataKind
+  DILocationMetadataKind                   = C.LLVMDILocationMetadataKind
+  DIExpressionMetadataKind                 = C.LLVMDIExpressionMetadataKind
+  DIGlobalVariableExpressionMetadataKind   = C.LLVMDIGlobalVariableExpressionMetadataKind
+  GenericDINodeMetadataKind                = C.LLVMGenericDINodeMetadataKind
+  DISubrangeMetadataKind                   = C.LLVMDISubrangeMetadataKind
+  DIEnumeratorMetadataKind                 = C.LLVMDIEnumeratorMetadataKind
+  DIBasicTypeMetadataKind                  = C.LLVMDIBasicTypeMetadataKind
+  DIDerivedTypeMetadataKind                = C.LLVMDIDerivedTypeMetadataKind
+  DICompositeTypeMetadataKind              = C.LLVMDICompositeTypeMetadataKind
+  DISubroutineTypeMetadataKind             = C.LLVMDISubroutineTypeMetadataKind
+  DIFileMetadataKind                       = C.LLVMDIFileMetadataKind
+  DICompileUnitMetadataKind                = C.LLVMDICompileUnitMetadataKind
+  DISubprogramMetadataKind                 = C.LLVMDISubprogramMetadataKind
+  DILexicalBlockMetadataKind               = C.LLVMDILexicalBlockMetadataKind
+  DILexicalBlockFileMetadataKind           = C.LLVMDILexicalBlockFileMetadataKind
+  DINamespaceMetadataKind                  = C.LLVMDINamespaceMetadataKind
+  DIModuleMetadataKind                     = C.LLVMDIModuleMetadataKind
+  DITemplateTypeParameterMetadataKind      = C.LLVMDITemplateTypeParameterMetadataKind
+  DITemplateValueParameterMetadataKind     = C.LLVMDITemplateValueParameterMetadataKind
+  DIGlobalVariableMetadataKind             = C.LLVMDIGlobalVariableMetadataKind
+  DILocalVariableMetadataKind              = C.LLVMDILocalVariableMetadataKind
+  DILabelMetadataKind                      = C.LLVMDILabelMetadataKind
+  DIObjCPropertyMetadataKind               = C.LLVMDIObjCPropertyMetadataKind
+  DIImportedEntityMetadataKind             = C.LLVMDIImportedEntityMetadataKind
+  DIMacroMetadataKind                      = C.LLVMDIMacroMetadataKind
+  DIMacroFileMetadataKind                  = C.LLVMDIMacroFileMetadataKind
+  DICommonBlockMetadataKind                = C.LLVMDICommonBlockMetadataKind
+)
+
+// Kind returns the metadata kind.
+func (md Metadata) Kind() MetadataKind {
+  return MetadataKind(C.LLVMGetMetadataKind(md.C))
+}
+
+// FileDirectory returns the directory of a DIFile metadata node.
+func (md Metadata) FileDirectory() string {
+  var length C.unsigned
+  ptr := C.LLVMDIFileGetDirectory(md.C, &length)
+  return string(((*[1 << 20]byte)(unsafe.Pointer(ptr)))[:length:length])
+}
+
+// FileFilename returns the filename of a DIFile metadata node.
+func (md Metadata) FileFilename() string {
+  var length C.unsigned
+  ptr := C.LLVMDIFileGetFilename(md.C, &length)
+  return string(((*[1 << 20]byte)(unsafe.Pointer(ptr)))[:length:length])
+}
+
+// FileSource returns the source of a DIFile metadata node.
+func (md Metadata) FileSource() string {
+  var length C.unsigned
+  ptr := C.LLVMDIFileGetSource(md.C, &length)
+  return string(((*[1 << 20]byte)(unsafe.Pointer(ptr)))[:length:length])
+}
+
+// LocationLine returns the line number of a DILocation.
+func (md Metadata) LocationLine() uint {
+  return uint(C.LLVMDILocationGetLine(md.C))
+}
+
+// LocationColumn returns the column (offset from the start of the line) of a
+// DILocation.
+func (md Metadata) LocationColumn() uint {
+  return uint(C.LLVMDILocationGetColumn(md.C))
+}
+
+// LocationScope returns the local scope associated with this debug location.
+func (md Metadata) LocationScope() Metadata {
+  return Metadata{C.LLVMDILocationGetScope(md.C)}
+}
+
+// LocationInlinedAt return the "inline at" location associated with this debug
+// location.
+func (md Metadata) LocationInlinedAt() Metadata {
+  return Metadata{C.LLVMDILocationGetInlinedAt(md.C)}
+}
+
+// ScopeFile returns the file (DIFile) of a given scope.
+func (md Metadata) ScopeFile() Metadata {
+  return Metadata{C.LLVMDIScopeGetFile(md.C)}
+}

ir.go

 func (c Value) IsNil() bool          { return c.C == nil }
 func (c BasicBlock) IsNil() bool     { return c.C == nil }
 func (c Builder) IsNil() bool        { return c.C == nil }
 func (c ModuleProvider) IsNil() bool { return c.C == nil }
 func (c MemoryBuffer) IsNil() bool   { return c.C == nil }
 func (c PassManager) IsNil() bool    { return c.C == nil }
 func (c Use) IsNil() bool            { return c.C == nil }
 func (c Attribute) IsNil() bool      { return c.C == nil }
+func (c Metadata) IsNil() bool       { return c.C == nil }
 
 // helpers
 func llvmTypeRefPtr(t *Type) *C.LLVMTypeRef    { return (*C.LLVMTypeRef)(unsafe.Pointer(t)) }
 func llvmValueRefPtr(t *Value) *C.LLVMValueRef { return (*C.LLVMValueRef)(unsafe.Pointer(t)) }
 func llvmMetadataRefPtr(t *Metadata) *C.LLVMMetadataRef {
   return (*C.LLVMMetadataRef)(unsafe.Pointer(t))
 }
 func llvmBasicBlockRefPtr(t *BasicBlock) *C.LLVMBasicBlockRef {
func InsertBasicBlock(ref BasicBlock, name string) (bb BasicBlock) {
   return
 }
 func (bb BasicBlock) EraseFromParent()          { C.LLVMDeleteBasicBlock(bb.C) }
 func (bb BasicBlock) MoveBefore(pos BasicBlock) { C.LLVMMoveBasicBlockBefore(bb.C, pos.C) }
 func (bb BasicBlock) MoveAfter(pos BasicBlock)  { C.LLVMMoveBasicBlockAfter(bb.C, pos.C) }
 
 // Operations on instructions
 func (v Value) InstructionParent() (bb BasicBlock) { bb.C = C.LLVMGetInstructionParent(v.C); return }
+func (v Value) InstructionDebugLoc() (md Metadata) { md.C = C.LLVMInstructionGetDebugLoc(v.C); return }
+func (v Value) InstructionSetDebugLoc(md Metadata) { C.LLVMInstructionSetDebugLoc(v.C, md.C) }
 func (bb BasicBlock) FirstInstruction() (v Value)  { v.C = C.LLVMGetFirstInstruction(bb.C); return }
 func (bb BasicBlock) LastInstruction() (v Value)   { v.C = C.LLVMGetLastInstruction(bb.C); return }
 func NextInstruction(v Value) (rv Value)           { rv.C = C.LLVMGetNextInstruction(v.C); return }
 func PrevInstruction(v Value) (rv Value)           { rv.C = C.LLVMGetPreviousInstruction(v.C); return }
 
 // Operations on call sites
 func (v Value) SetInstructionCallConv(cc CallConv) {
   C.LLVMSetInstructionCallConv(v.C, C.unsigned(cc))