Add methods to read debug information from IR

This was previously pushed to LLVM master, but did not land in LLVM 9
yet:
https://reviews.llvm.org/D63056

The patch was slightly modified to fix some small issues.

dibuilder.go

@@ -604,3 +604,109 @@ func (c Context) TemporaryMDNode(mds []Metadata) (md Metadata) {
 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, or the empty
+// string if there is no directory information.
+func (md Metadata) FileDirectory() string {
+	var length C.unsigned
+	ptr := C.LLVMDIFileGetDirectory(md.C, &length)
+	if ptr == nil {
+		return ""
+	}
+	return string(((*[1 << 20]byte)(unsafe.Pointer(ptr)))[:length:length])
+}
+
+// FileFilename returns the filename of a DIFile metadata node, or the empty
+// string if there is no filename information.
+func (md Metadata) FileFilename() string {
+	var length C.unsigned
+	ptr := C.LLVMDIFileGetFilename(md.C, &length)
+	if ptr == nil {
+		return ""
+	}
+	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)
+	if ptr == nil {
+		return ""
+	}
+	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)}
+}
+
+// SubprogramLine returns the line number of a DISubprogram.
+func (md Metadata) SubprogramLine() uint {
+	return uint(C.LLVMDISubprogramGetLine(md.C))
+}

ir.go

@@ -87,6 +87,7 @@ 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)) }
@@ -1209,6 +1210,8 @@ func (bb BasicBlock) MoveAfter(pos BasicBlock)  { C.LLVMMoveBasicBlockAfter(bb.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 }