compiler: add debug info for function arguments

This commit adds debug info to function arguments, so that in many cases
you can see them when compiling with less optimizations enabled.
Unfortunately, due to the way Go SSA works, it is hard to preserve them
in many cases.
Local variables are not yet saved.

Also, change the language type to C, to make sure lldb shows function
arguments. The previous language was Modula 3, apparently due to a
off-by-one error somewhere.

compiler/calls.go

@@ -55,6 +55,25 @@ func (c *Compiler) expandFormalParamType(t llvm.Type) []llvm.Type {
 	}
 }
 
+// Expand an argument type to a list of offsets from the start of the object.
+// Used together with expandFormalParam to get the offset of each value from the
+// start of the non-expanded value.
+func (c *Compiler) expandFormalParamOffsets(t llvm.Type) []uint64 {
+	switch t.TypeKind() {
+	case llvm.StructTypeKind:
+		fields := c.flattenAggregateTypeOffsets(t)
+		if len(fields) <= MaxFieldsPerParam {
+			return fields
+		} else {
+			// failed to lower
+			return []uint64{0}
+		}
+	default:
+		// TODO: split small arrays
+		return []uint64{0}
+	}
+}
+
 // Equivalent of expandFormalParamType for parameter values.
 func (c *Compiler) expandFormalParam(v llvm.Value) []llvm.Value {
 	switch v.Type().TypeKind() {
@@ -92,6 +111,27 @@ func (c *Compiler) flattenAggregateType(t llvm.Type) []llvm.Type {
 	}
 }
 
+// Return the offsets from the start of the object if this object type were
+// flattened like in flattenAggregate. Used together with flattenAggregate to
+// know the start indices of each value in the non-flattened object.
+func (c *Compiler) flattenAggregateTypeOffsets(t llvm.Type) []uint64 {
+	switch t.TypeKind() {
+	case llvm.StructTypeKind:
+		fields := make([]uint64, 0, t.StructElementTypesCount())
+		for fieldIndex, field := range t.StructElementTypes() {
+			suboffsets := c.flattenAggregateTypeOffsets(field)
+			offset := c.targetData.ElementOffset(t, fieldIndex)
+			for i := range suboffsets {
+				suboffsets[i] += offset
+			}
+			fields = append(fields, suboffsets...)
+		}
+		return fields
+	default:
+		return []uint64{0}
+	}
+}
+
 // Break down a struct into its elementary types for argument passing. The value
 // equivalent of flattenAggregateType
 func (c *Compiler) flattenAggregate(v llvm.Value) []llvm.Value {

compiler/compiler.go

@@ -52,7 +52,6 @@ type Compiler struct {
 	dibuilder               *llvm.DIBuilder
 	cu                      llvm.Metadata
 	difiles                 map[string]llvm.Metadata
-	ditypes                 map[string]llvm.Metadata
 	machine                 llvm.TargetMachine
 	targetData              llvm.TargetData
 	intType                 llvm.Type
@@ -96,7 +95,6 @@ func NewCompiler(pkgName string, config Config) (*Compiler, error) {
 	c := &Compiler{
 		Config:  config,
 		difiles: make(map[string]llvm.Metadata),
-		ditypes: make(map[string]llvm.Metadata),
 	}
 
 	target, err := llvm.GetTargetFromTriple(config.Triple)
@@ -252,7 +250,7 @@ func (c *Compiler) Compile(mainPath string) []error {
 	// Initialize debug information.
 	if c.Debug {
 		c.cu = c.dibuilder.CreateCompileUnit(llvm.DICompileUnit{
-			Language:  llvm.DW_LANG_Go,
+			Language:  0xb, // DW_LANG_C99 (0xc, off-by-one?)
 			File:      mainPath,
 			Dir:       "",
 			Producer:  "TinyGo",
@@ -387,6 +385,13 @@ func (c *Compiler) Compile(mainPath string) []error {
 				llvm.ConstInt(c.ctx.Int32Type(), 3, false).ConstantAsMetadata(), // DWARF version
 			}),
 		)
+		c.mod.AddNamedMetadataOperand("llvm.module.flags",
+			c.ctx.MDNode([]llvm.Metadata{
+				llvm.ConstInt(c.ctx.Int32Type(), 1, false).ConstantAsMetadata(),
+				llvm.GlobalContext().MDString("Dwarf Version"),
+				llvm.ConstInt(c.ctx.Int32Type(), 4, false).ConstantAsMetadata(),
+			}),
+		)
 		c.dibuilder.Finalize()
 	}
 
@@ -550,15 +555,23 @@ func isPointer(typ types.Type) bool {
 
 // Get the DWARF type for this Go type.
 func (c *Compiler) getDIType(typ types.Type) llvm.Metadata {
-	name := typ.String()
-	if dityp, ok := c.ditypes[name]; ok {
-		return dityp
-	} else {
 	llvmType := c.getLLVMType(typ)
 	sizeInBytes := c.targetData.TypeAllocSize(llvmType)
-		var encoding llvm.DwarfTypeEncoding
 	switch typ := typ.(type) {
+	case *types.Array:
+		return c.dibuilder.CreateArrayType(llvm.DIArrayType{
+			SizeInBits:  sizeInBytes * 8,
+			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+			ElementType: c.getDIType(typ.Elem()),
+			Subscripts: []llvm.DISubrange{
+				llvm.DISubrange{
+					Lo:    0,
+					Count: typ.Len(),
+				},
+			},
+		})
 	case *types.Basic:
+		var encoding llvm.DwarfTypeEncoding
 		if typ.Info()&types.IsBoolean != 0 {
 			encoding = llvm.DW_ATE_boolean
 		} else if typ.Info()&types.IsFloat != 0 {
@@ -570,19 +583,138 @@ func (c *Compiler) getDIType(typ types.Type) llvm.Metadata {
 		} else if typ.Info()&types.IsInteger != 0 {
 			encoding = llvm.DW_ATE_signed
 		} else if typ.Kind() == types.UnsafePointer {
-				encoding = llvm.DW_ATE_address
+			return c.dibuilder.CreatePointerType(llvm.DIPointerType{
+				Name:         "unsafe.Pointer",
+				SizeInBits:   c.targetData.TypeAllocSize(llvmType) * 8,
+				AlignInBits:  uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+				AddressSpace: 0,
+			})
+		} else if typ.Info()&types.IsString != 0 {
+			return c.dibuilder.CreateStructType(llvm.Metadata{}, llvm.DIStructType{
+				Name:        "string",
+				SizeInBits:  sizeInBytes * 8,
+				AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+				Elements: []llvm.Metadata{
+					c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+						Name:         "ptr",
+						SizeInBits:   c.targetData.TypeAllocSize(c.i8ptrType) * 8,
+						AlignInBits:  uint32(c.targetData.ABITypeAlignment(c.i8ptrType)) * 8,
+						OffsetInBits: 0,
+						Type:         c.getDIType(types.NewPointer(types.Typ[types.Byte])),
+					}),
+					c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+						Name:         "len",
+						SizeInBits:   c.targetData.TypeAllocSize(c.uintptrType) * 8,
+						AlignInBits:  uint32(c.targetData.ABITypeAlignment(c.uintptrType)) * 8,
+						OffsetInBits: c.targetData.ElementOffset(llvmType, 1) * 8,
+						Type:         c.getDIType(types.Typ[types.Uintptr]),
+					}),
+				},
+			})
+		} else {
+			panic("unknown basic type")
 		}
+		return c.dibuilder.CreateBasicType(llvm.DIBasicType{
+			Name:       typ.String(),
+			SizeInBits: sizeInBytes * 8,
+			Encoding:   encoding,
+		})
+	case *types.Chan:
+		return c.getDIType(types.NewPointer(c.ir.Program.ImportedPackage("runtime").Members["channel"].(*ssa.Type).Type()))
+	case *types.Interface:
+		return c.getDIType(c.ir.Program.ImportedPackage("runtime").Members["_interface"].(*ssa.Type).Type())
+	case *types.Map:
+		return c.getDIType(types.NewPointer(c.ir.Program.ImportedPackage("runtime").Members["hashmap"].(*ssa.Type).Type()))
+	case *types.Named:
+		return c.dibuilder.CreateTypedef(llvm.DITypedef{
+			Type: c.getDIType(typ.Underlying()),
+			Name: typ.String(),
+		})
 	case *types.Pointer:
-			encoding = llvm.DW_ATE_address
+		return c.dibuilder.CreatePointerType(llvm.DIPointerType{
+			Pointee:      c.getDIType(typ.Elem()),
+			SizeInBits:   c.targetData.TypeAllocSize(llvmType) * 8,
+			AlignInBits:  uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+			AddressSpace: 0,
+		})
+	case *types.Signature:
+		// actually a closure
+		fields := llvmType.StructElementTypes()
+		return c.dibuilder.CreateStructType(llvm.Metadata{}, llvm.DIStructType{
+			SizeInBits:  sizeInBytes * 8,
+			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+			Elements: []llvm.Metadata{
+				c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+					Name:         "context",
+					SizeInBits:   c.targetData.TypeAllocSize(fields[1]) * 8,
+					AlignInBits:  uint32(c.targetData.ABITypeAlignment(fields[1])) * 8,
+					OffsetInBits: 0,
+					Type:         c.getDIType(types.Typ[types.UnsafePointer]),
+				}),
+				c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+					Name:         "fn",
+					SizeInBits:   c.targetData.TypeAllocSize(fields[0]) * 8,
+					AlignInBits:  uint32(c.targetData.ABITypeAlignment(fields[0])) * 8,
+					OffsetInBits: c.targetData.ElementOffset(llvmType, 1) * 8,
+					Type:         c.getDIType(types.Typ[types.UnsafePointer]),
+				}),
+			},
+		})
+	case *types.Slice:
+		fields := llvmType.StructElementTypes()
+		return c.dibuilder.CreateStructType(llvm.Metadata{}, llvm.DIStructType{
+			Name:        typ.String(),
+			SizeInBits:  sizeInBytes * 8,
+			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+			Elements: []llvm.Metadata{
+				c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+					Name:         "ptr",
+					SizeInBits:   c.targetData.TypeAllocSize(fields[0]) * 8,
+					AlignInBits:  uint32(c.targetData.ABITypeAlignment(fields[0])) * 8,
+					OffsetInBits: 0,
+					Type:         c.getDIType(types.NewPointer(typ.Elem())),
+				}),
+				c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+					Name:         "len",
+					SizeInBits:   c.targetData.TypeAllocSize(c.uintptrType) * 8,
+					AlignInBits:  uint32(c.targetData.ABITypeAlignment(c.uintptrType)) * 8,
+					OffsetInBits: c.targetData.ElementOffset(llvmType, 1) * 8,
+					Type:         c.getDIType(types.Typ[types.Uintptr]),
+				}),
+				c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+					Name:         "cap",
+					SizeInBits:   c.targetData.TypeAllocSize(c.uintptrType) * 8,
+					AlignInBits:  uint32(c.targetData.ABITypeAlignment(c.uintptrType)) * 8,
+					OffsetInBits: c.targetData.ElementOffset(llvmType, 2) * 8,
+					Type:         c.getDIType(types.Typ[types.Uintptr]),
+				}),
+			},
+		})
+	case *types.Struct:
+		elements := make([]llvm.Metadata, typ.NumFields())
+		for i := range elements {
+			field := typ.Field(i)
+			fieldType := field.Type()
+			if _, ok := fieldType.Underlying().(*types.Pointer); ok {
+				// XXX hack to avoid recursive types
+				fieldType = types.Typ[types.UnsafePointer]
+			}
+			llvmField := c.getLLVMType(fieldType)
+			elements[i] = c.dibuilder.CreateMemberType(llvm.Metadata{}, llvm.DIMemberType{
+				Name:         field.Name(),
+				SizeInBits:   c.targetData.TypeAllocSize(llvmField) * 8,
+				AlignInBits:  uint32(c.targetData.ABITypeAlignment(llvmField)) * 8,
+				OffsetInBits: c.targetData.ElementOffset(llvmType, i) * 8,
+				Type:         c.getDIType(fieldType),
+			})
 		}
-		// TODO: other types
-		dityp = c.dibuilder.CreateBasicType(llvm.DIBasicType{
-			Name:       name,
+		return c.dibuilder.CreateStructType(llvm.Metadata{}, llvm.DIStructType{
 			SizeInBits:  sizeInBytes * 8,
-			Encoding:   encoding,
+			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+			Elements:    elements,
 		})
-		c.ditypes[name] = dityp
-		return dityp
+	default:
+		panic("unknown type while generating DWARF debug type: " + typ.String())
 	}
 }
 
@@ -733,15 +865,30 @@ func (c *Compiler) parseFunc(frame *Frame) {
 		// Add debug information to this parameter (if available)
 		if c.Debug && frame.fn.Syntax() != nil {
 			pos := c.ir.Program.Fset.Position(frame.fn.Syntax().Pos())
-			c.dibuilder.CreateParameterVariable(frame.difunc, llvm.DIParameterVariable{
+			diType := c.getDIType(param.Type())
+			dbgParam := c.dibuilder.CreateParameterVariable(frame.difunc, llvm.DIParameterVariable{
 				Name:           param.Name(),
 				File:           c.difiles[pos.Filename],
 				Line:           pos.Line,
-				Type:           c.getDIType(param.Type()),
+				Type:           diType,
 				AlwaysPreserve: true,
 				ArgNo:          i + 1,
 			})
-			// TODO: set the value of this parameter.
+			loc := c.builder.GetCurrentDebugLocation()
+			if len(fields) == 1 {
+				expr := c.dibuilder.CreateExpression(nil)
+				c.dibuilder.InsertValueAtEnd(fields[0], dbgParam, expr, loc, entryBlock)
+			} else {
+				fieldOffsets := c.expandFormalParamOffsets(llvmType)
+				for i, field := range fields {
+					expr := c.dibuilder.CreateExpression([]int64{
+						0x1000,                     // DW_OP_LLVM_fragment
+						int64(fieldOffsets[i]) * 8, // offset in bits
+						int64(c.targetData.TypeAllocSize(field.Type())) * 8, // size in bits
+					})
+					c.dibuilder.InsertValueAtEnd(field, dbgParam, expr, loc, entryBlock)
+				}
+			}
 		}
 	}
 

interp/frame.go

@@ -347,6 +347,8 @@ func (fr *frame) evalBasicBlock(bb, incoming llvm.BasicBlock, indent string) (re
 				fr.locals[inst] = &LocalValue{fr.Eval, llvm.ConstInt(fr.Mod.Context().Int1Type(), implements, false)}
 			case callee.Name() == "runtime.nanotime":
 				fr.locals[inst] = &LocalValue{fr.Eval, llvm.ConstInt(fr.Mod.Context().Int64Type(), 0, false)}
+			case callee.Name() == "llvm.dbg.value":
+				// do nothing
 			case strings.HasPrefix(callee.Name(), "runtime.print") || callee.Name() == "runtime._panic":
 				// This are all print instructions, which necessarily have side
 				// effects but no results.

interp/interp.go

@@ -18,7 +18,6 @@ type Eval struct {
 	TargetData      llvm.TargetData
 	Debug           bool
 	builder         llvm.Builder
-	dibuilder       *llvm.DIBuilder
 	dirtyGlobals    map[llvm.Value]struct{}
 	sideEffectFuncs map[llvm.Value]*sideEffectResult // cache of side effect scan results
 }
@@ -38,7 +37,6 @@ func Run(mod llvm.Module, targetData llvm.TargetData, debug bool) error {
 		dirtyGlobals: map[llvm.Value]struct{}{},
 	}
 	e.builder = mod.Context().NewBuilder()
-	e.dibuilder = llvm.NewDIBuilder(mod)
 
 	initAll := mod.NamedFunction(name)
 	bb := initAll.EntryBasicBlock()
@@ -49,7 +47,6 @@ func Run(mod llvm.Module, targetData llvm.TargetData, debug bool) error {
 	e.builder.SetInsertPointBefore(bb.FirstInstruction())
 	dummy := e.builder.CreateAlloca(e.Mod.Context().Int8Type(), "dummy")
 	e.builder.SetInsertPointBefore(dummy)
-	e.builder.SetInstDebugLocation(bb.FirstInstruction())
 	var initCalls []llvm.Value
 	for inst := bb.FirstInstruction(); !inst.IsNil(); inst = llvm.NextInstruction(inst) {
 		if inst == dummy {

interp/scan.go

@@ -35,6 +35,8 @@ func (e *Eval) hasSideEffects(fn llvm.Value) *sideEffectResult {
 		return &sideEffectResult{severity: sideEffectLimited}
 	case "runtime.interfaceImplements":
 		return &sideEffectResult{severity: sideEffectNone}
+	case "llvm.dbg.value":
+		return &sideEffectResult{severity: sideEffectNone}
 	}
 	if e.sideEffectFuncs == nil {
 		e.sideEffectFuncs = make(map[llvm.Value]*sideEffectResult)