Merge pull request #13495 from ziglang/macho-dsym

stage2: misc DWARF debug info fixes and additions for x86_64 and aarch64

src/arch/aarch64/CodeGen.zig

@@ -51,13 +51,14 @@ gpa: Allocator,
 air: Air,
 liveness: Liveness,
 bin_file: *link.File,
+debug_output: DebugInfoOutput,
 target: *const std.Target,
 mod_fn: *const Module.Fn,
 err_msg: ?*ErrorMsg,
 args: []MCValue,
 ret_mcv: MCValue,
 fn_type: Type,
-arg_index: usize,
+arg_index: u32,
 src_loc: Module.SrcLoc,
 stack_align: u32,
 
@@ -75,6 +76,12 @@ end_di_column: u32,
 /// which is a relative jump, based on the address following the reloc.
 exitlude_jump_relocs: std.ArrayListUnmanaged(usize) = .{},
 
+/// We postpone the creation of debug info for function args and locals
+/// until after all Mir instructions have been generated. Only then we
+/// will know saved_regs_stack_space which is necessary in order to
+/// calculate the right stack offsest with respect to the `.fp` register.
+dbg_info_relocs: std.ArrayListUnmanaged(DbgInfoReloc) = .{},
+
 /// Whenever there is a runtime branch, we push a Branch onto this stack,
 /// and pop it off when the runtime branch joins. This provides an "overlay"
 /// of the table of mappings from instructions to `MCValue` from within the branch.
@@ -160,6 +167,220 @@ const MCValue = union(enum) {
     stack_argument_offset: u32,
 };
 
+const DbgInfoReloc = struct {
+    tag: Air.Inst.Tag,
+    ty: Type,
+    name: [:0]const u8,
+    mcv: MCValue,
+
+    fn genDbgInfo(reloc: DbgInfoReloc, function: Self) !void {
+        switch (reloc.tag) {
+            .arg => try reloc.genArgDbgInfo(function),
+
+            .dbg_var_ptr,
+            .dbg_var_val,
+            => try reloc.genVarDbgInfo(function),
+
+            else => unreachable,
+        }
+    }
+
+    fn genArgDbgInfo(reloc: DbgInfoReloc, function: Self) error{OutOfMemory}!void {
+        const name_with_null = reloc.name.ptr[0 .. reloc.name.len + 1];
+
+        switch (function.debug_output) {
+            .dwarf => |dw| {
+                const dbg_info = &dw.dbg_info;
+                switch (reloc.mcv) {
+                    .register => |reg| {
+                        try dbg_info.ensureUnusedCapacity(3);
+                        dbg_info.appendAssumeCapacity(@enumToInt(link.File.Dwarf.AbbrevKind.parameter));
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1, // ULEB128 dwarf expression length
+                            reg.dwarfLocOp(),
+                        });
+                        try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
+                        try function.addDbgInfoTypeReloc(reloc.ty); // DW.AT.type,  DW.FORM.ref4
+                        dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
+                    },
+
+                    .stack_offset,
+                    .stack_argument_offset,
+                    => |offset| {
+                        const adjusted_offset = switch (reloc.mcv) {
+                            .stack_offset => -@intCast(i32, offset),
+                            .stack_argument_offset => @intCast(i32, function.saved_regs_stack_space + offset),
+                            else => unreachable,
+                        };
+
+                        try dbg_info.ensureUnusedCapacity(8);
+                        dbg_info.appendAssumeCapacity(@enumToInt(link.File.Dwarf.AbbrevKind.parameter));
+                        const fixup = dbg_info.items.len;
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1, // we will backpatch it after we encode the displacement in LEB128
+                            Register.x29.dwarfLocOpDeref(), // frame pointer
+                        });
+                        leb128.writeILEB128(dbg_info.writer(), adjusted_offset) catch unreachable;
+                        dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
+                        try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
+                        try function.addDbgInfoTypeReloc(reloc.ty); // DW.AT.type,  DW.FORM.ref4
+                        dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
+
+                    },
+
+                    else => unreachable, // not a possible argument
+                }
+            },
+            .plan9 => {},
+            .none => {},
+        }
+    }
+
+    fn genVarDbgInfo(reloc: DbgInfoReloc, function: Self) !void {
+        const name_with_null = reloc.name.ptr[0 .. reloc.name.len + 1];
+        const ty = switch (reloc.tag) {
+            .dbg_var_ptr => reloc.ty.childType(),
+            .dbg_var_val => reloc.ty,
+            else => unreachable,
+        };
+
+        switch (function.debug_output) {
+            .dwarf => |dw| {
+                const dbg_info = &dw.dbg_info;
+                try dbg_info.append(@enumToInt(link.File.Dwarf.AbbrevKind.variable));
+                const endian = function.target.cpu.arch.endian();
+
+                switch (reloc.mcv) {
+                    .register => |reg| {
+                        try dbg_info.ensureUnusedCapacity(2);
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1, // ULEB128 dwarf expression length
+                            reg.dwarfLocOp(),
+                        });
+                    },
+
+                    .ptr_stack_offset,
+                    .stack_offset,
+                    .stack_argument_offset,
+                    => |offset| {
+                        const adjusted_offset = switch (reloc.mcv) {
+                            .ptr_stack_offset,
+                            .stack_offset,
+                            => -@intCast(i32, offset),
+                            .stack_argument_offset => @intCast(i32, function.saved_regs_stack_space + offset),
+                            else => unreachable,
+                        };
+
+                        try dbg_info.ensureUnusedCapacity(7);
+                        const fixup = dbg_info.items.len;
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1, // we will backpatch it after we encode the displacement in LEB128
+                            Register.x29.dwarfLocOpDeref(), // frame pointer
+                        });
+                        leb128.writeILEB128(dbg_info.writer(), adjusted_offset) catch unreachable;
+                        dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
+                    },
+
+                    .memory,
+                    .linker_load,
+                    => {
+                        const ptr_width = @intCast(u8, @divExact(function.target.cpu.arch.ptrBitWidth(), 8));
+                        const is_ptr = switch (reloc.tag) {
+                            .dbg_var_ptr => true,
+                            .dbg_var_val => false,
+                            else => unreachable,
+                        };
+                        try dbg_info.ensureUnusedCapacity(2 + ptr_width);
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1 + ptr_width + @boolToInt(is_ptr),
+                            DW.OP.addr, // literal address
+                        });
+                        const offset = @intCast(u32, dbg_info.items.len);
+                        const addr = switch (reloc.mcv) {
+                            .memory => |addr| addr,
+                            else => 0,
+                        };
+                        switch (ptr_width) {
+                            0...4 => {
+                                try dbg_info.writer().writeInt(u32, @intCast(u32, addr), endian);
+                            },
+                            5...8 => {
+                                try dbg_info.writer().writeInt(u64, addr, endian);
+                            },
+                            else => unreachable,
+                        }
+                        if (is_ptr) {
+                            // We need deref the address as we point to the value via GOT entry.
+                            try dbg_info.append(DW.OP.deref);
+                        }
+                        switch (reloc.mcv) {
+                            .linker_load => |load_struct| try dw.addExprlocReloc(
+                                load_struct.sym_index,
+                                offset,
+                                is_ptr,
+                            ),
+                            else => {},
+                        }
+                    },
+
+                    .immediate => |x| {
+                        try dbg_info.ensureUnusedCapacity(2);
+                        const fixup = dbg_info.items.len;
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1,
+                            if (ty.isSignedInt()) DW.OP.consts else DW.OP.constu,
+                        });
+                        if (ty.isSignedInt()) {
+                            try leb128.writeILEB128(dbg_info.writer(), @bitCast(i64, x));
+                        } else {
+                            try leb128.writeULEB128(dbg_info.writer(), x);
+                        }
+                        try dbg_info.append(DW.OP.stack_value);
+                        dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
+                    },
+
+                    .undef => {
+                        // DW.AT.location, DW.FORM.exprloc
+                        // uleb128(exprloc_len)
+                        // DW.OP.implicit_value uleb128(len_of_bytes) bytes
+                        const abi_size = @intCast(u32, ty.abiSize(function.target.*));
+                        var implicit_value_len = std.ArrayList(u8).init(function.gpa);
+                        defer implicit_value_len.deinit();
+                        try leb128.writeULEB128(implicit_value_len.writer(), abi_size);
+                        const total_exprloc_len = 1 + implicit_value_len.items.len + abi_size;
+                        try leb128.writeULEB128(dbg_info.writer(), total_exprloc_len);
+                        try dbg_info.ensureUnusedCapacity(total_exprloc_len);
+                        dbg_info.appendAssumeCapacity(DW.OP.implicit_value);
+                        dbg_info.appendSliceAssumeCapacity(implicit_value_len.items);
+                        dbg_info.appendNTimesAssumeCapacity(0xaa, abi_size);
+                    },
+
+                    .none => {
+                        try dbg_info.ensureUnusedCapacity(3);
+                        dbg_info.appendSliceAssumeCapacity(&[3]u8{ // DW.AT.location, DW.FORM.exprloc
+                            2, DW.OP.lit0, DW.OP.stack_value,
+                        });
+                    },
+
+                    else => {
+                        try dbg_info.ensureUnusedCapacity(2);
+                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                            1, DW.OP.nop,
+                        });
+                        log.debug("TODO generate debug info for {}", .{reloc.mcv});
+                    },
+                }
+
+                try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
+                try function.addDbgInfoTypeReloc(ty); // DW.AT.type,  DW.FORM.ref4
+                dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
+            },
+            .plan9 => {},
+            .none => {},
+        }
+    }
+};
+
 const Branch = struct {
     inst_table: std.AutoArrayHashMapUnmanaged(Air.Inst.Index, MCValue) = .{},
 
@@ -262,6 +483,7 @@ pub fn generate(
         .gpa = bin_file.allocator,
         .air = air,
         .liveness = liveness,
+        .debug_output = debug_output,
         .target = &bin_file.options.target,
         .bin_file = bin_file,
         .mod_fn = module_fn,
@@ -279,6 +501,7 @@ pub fn generate(
     defer function.stack.deinit(bin_file.allocator);
     defer function.blocks.deinit(bin_file.allocator);
     defer function.exitlude_jump_relocs.deinit(bin_file.allocator);
+    defer function.dbg_info_relocs.deinit(bin_file.allocator);
 
     var call_info = function.resolveCallingConventionValues(fn_type) catch |err| switch (err) {
         error.CodegenFail => return FnResult{ .fail = function.err_msg.? },
@@ -302,6 +525,10 @@ pub fn generate(
         else => |e| return e,
     };
 
+    for (function.dbg_info_relocs.items) |reloc| {
+        try reloc.genDbgInfo(function);
+    }
+
     var mir = Mir{
         .instructions = function.mir_instructions.toOwnedSlice(),
         .extra = function.mir_extra.toOwnedSlice(bin_file.allocator),
@@ -854,23 +1081,20 @@ fn ensureProcessDeathCapacity(self: *Self, additional_count: usize) !void {
 
 /// Adds a Type to the .debug_info at the current position. The bytes will be populated later,
 /// after codegen for this symbol is done.
-fn addDbgInfoTypeReloc(self: *Self, ty: Type) !void {
+fn addDbgInfoTypeReloc(self: Self, ty: Type) !void {
     switch (self.debug_output) {
-        .dwarf => |dbg_out| {
-            assert(ty.hasRuntimeBits());
-            const index = dbg_out.dbg_info.items.len;
-            try dbg_out.dbg_info.resize(index + 4); // DW.AT.type,  DW.FORM.ref4
-
-            const gop = try dbg_out.dbg_info_type_relocs.getOrPutContext(self.gpa, ty, .{
-                .target = self.target.*,
-            });
-            if (!gop.found_existing) {
-                gop.value_ptr.* = .{
-                    .off = undefined,
-                    .relocs = .{},
-                };
-            }
-            try gop.value_ptr.relocs.append(self.gpa, @intCast(u32, index));
+        .dwarf => |dw| {
+            const dbg_info = &dw.dbg_info;
+            const index = dbg_info.items.len;
+            try dbg_info.resize(index + 4); // DW.AT.type,  DW.FORM.ref4
+            const mod = self.bin_file.options.module.?;
+            const fn_owner_decl = mod.declPtr(self.mod_fn.owner_decl);
+            const atom = switch (self.bin_file.tag) {
+                .elf => &fn_owner_decl.link.elf.dbg_info_atom,
+                .macho => &fn_owner_decl.link.macho.dbg_info_atom,
+                else => unreachable,
+            };
+            try dw.addTypeRelocGlobal(atom, ty, @intCast(u32, index));
         },
         .plan9 => {},
         .none => {},
@@ -3957,8 +4181,9 @@ fn airArg(self: *Self, inst: Air.Inst.Index) !void {
     self.arg_index += 1;
 
     const ty = self.air.typeOfIndex(inst);
-
     const result = self.args[arg_index];
+    const name = self.mod_fn.getParamName(self.bin_file.options.module.?, arg_index);
+
     const mcv = switch (result) {
         // Copy registers to the stack
         .register => |reg| blk: {
@@ -3974,8 +4199,14 @@ fn airArg(self: *Self, inst: Air.Inst.Index) !void {
         },
         else => result,
     };
-    // TODO generate debug info
-    // try self.genArgDbgInfo(inst, mcv);
+
+    const tag = self.air.instructions.items(.tag)[inst];
+    try self.dbg_info_relocs.append(self.gpa, .{
+        .tag = tag,
+        .ty = ty,
+        .name = name,
+        .mcv = result,
+    });
 
     if (self.liveness.isUnused(inst))
         return self.finishAirBookkeeping();
@@ -4463,10 +4694,21 @@ fn airDbgBlock(self: *Self, inst: Air.Inst.Index) !void {
 
 fn airDbgVar(self: *Self, inst: Air.Inst.Index) !void {
     const pl_op = self.air.instructions.items(.data)[inst].pl_op;
-    const name = self.air.nullTerminatedString(pl_op.payload);
     const operand = pl_op.operand;
-    // TODO emit debug info for this variable
-    _ = name;
+    const tag = self.air.instructions.items(.tag)[inst];
+    const ty = self.air.typeOf(operand);
+    const mcv = try self.resolveInst(operand);
+    const name = self.air.nullTerminatedString(pl_op.payload);
+
+    log.debug("airDbgVar: %{d}: {}, {}", .{ inst, ty.fmtDebug(), mcv });
+
+    try self.dbg_info_relocs.append(self.gpa, .{
+        .tag = tag,
+        .ty = ty,
+        .name = name,
+        .mcv = mcv,
+    });
+
     return self.finishAir(inst, .dead, .{ operand, .none, .none });
 }
 

src/arch/aarch64/bits.zig

@@ -296,6 +296,13 @@ pub const Register = enum(u8) {
     pub fn dwarfLocOp(self: Register) u8 {
         return @as(u8, self.enc()) + DW.OP.reg0;
     }
+
+    /// DWARF encodings that push a value onto the DWARF stack that is either
+    /// the contents of a register or the result of adding the contents a given
+    /// register to a given signed offset.
+    pub fn dwarfLocOpDeref(self: Register) u8 {
+        return @as(u8, self.enc()) + DW.OP.breg0;
+    }
 };
 
 test "Register.enc" {

src/arch/x86_64/CodeGen.zig

@@ -3797,64 +3797,68 @@ fn airArg(self: *Self, inst: Air.Inst.Index) !void {
     const ty = self.air.typeOfIndex(inst);
     const mcv = self.args[arg_index];
     const name = self.mod_fn.getParamName(self.bin_file.options.module.?, arg_index);
-    const name_with_null = name.ptr[0 .. name.len + 1];
 
     if (self.liveness.isUnused(inst))
         return self.finishAirBookkeeping();
 
-    const dst_mcv: MCValue = blk: {
-        switch (mcv) {
-            .register => |reg| {
-                self.register_manager.getRegAssumeFree(reg.to64(), inst);
-                switch (self.debug_output) {
-                    .dwarf => |dw| {
-                        const dbg_info = &dw.dbg_info;
-                        try dbg_info.ensureUnusedCapacity(3);
-                        dbg_info.appendAssumeCapacity(@enumToInt(link.File.Dwarf.AbbrevKind.parameter));
-                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
-                            1, // ULEB128 dwarf expression length
-                            reg.dwarfLocOp(),
-                        });
-                        try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
-                        try self.addDbgInfoTypeReloc(ty); // DW.AT.type,  DW.FORM.ref4
-                        dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
-                    },
-                    .plan9 => {},
-                    .none => {},
-                }
-                break :blk mcv;
-            },
-            .stack_offset => |off| {
-                const offset = @intCast(i32, self.max_end_stack) - off + 16;
-                switch (self.debug_output) {
-                    .dwarf => |dw| {
-                        const dbg_info = &dw.dbg_info;
-                        try dbg_info.ensureUnusedCapacity(8);
-                        dbg_info.appendAssumeCapacity(@enumToInt(link.File.Dwarf.AbbrevKind.parameter));
-                        const fixup = dbg_info.items.len;
-                        dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
-                            1, // we will backpatch it after we encode the displacement in LEB128
-                            DW.OP.breg6, // .rbp TODO handle -fomit-frame-pointer
-                        });
-                        leb128.writeILEB128(dbg_info.writer(), offset) catch unreachable;
-                        dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
-                        try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
-                        try self.addDbgInfoTypeReloc(ty); // DW.AT.type,  DW.FORM.ref4
-                        dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
-
-                    },
-                    .plan9 => {},
-                    .none => {},
-                }
-                break :blk MCValue{ .stack_offset = -offset };
-            },
-            else => return self.fail("TODO implement arg for {}", .{mcv}),
-        }
+    const dst_mcv: MCValue = switch (mcv) {
+        .register => |reg| blk: {
+            self.register_manager.getRegAssumeFree(reg.to64(), inst);
+            break :blk MCValue{ .register = reg };
+        },
+        .stack_offset => |off| blk: {
+            const offset = @intCast(i32, self.max_end_stack) - off + 16;
+            break :blk MCValue{ .stack_offset = -offset };
+        },
+        else => return self.fail("TODO implement arg for {}", .{mcv}),
     };
+    try self.genArgDbgInfo(ty, name, dst_mcv);
 
     return self.finishAir(inst, dst_mcv, .{ .none, .none, .none });
 }
 
+fn genArgDbgInfo(self: Self, ty: Type, name: [:0]const u8, mcv: MCValue) !void {
+    const name_with_null = name.ptr[0 .. name.len + 1];
+    switch (self.debug_output) {
+        .dwarf => |dw| {
+            const dbg_info = &dw.dbg_info;
+            switch (mcv) {
+                .register => |reg| {
+                    try dbg_info.ensureUnusedCapacity(3);
+                    dbg_info.appendAssumeCapacity(@enumToInt(link.File.Dwarf.AbbrevKind.parameter));
+                    dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                        1, // ULEB128 dwarf expression length
+                        reg.dwarfLocOp(),
+                    });
+                    try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
+                    try self.addDbgInfoTypeReloc(ty); // DW.AT.type,  DW.FORM.ref4
+                    dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
+                },
+
+                .stack_offset => |off| {
+                    try dbg_info.ensureUnusedCapacity(8);
+                    dbg_info.appendAssumeCapacity(@enumToInt(link.File.Dwarf.AbbrevKind.parameter));
+                    const fixup = dbg_info.items.len;
+                    dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
+                        1, // we will backpatch it after we encode the displacement in LEB128
+                        Register.rbp.dwarfLocOpDeref(), // TODO handle -fomit-frame-pointer
+                    });
+                    leb128.writeILEB128(dbg_info.writer(), -off) catch unreachable;
+                    dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
+                    try dbg_info.ensureUnusedCapacity(5 + name_with_null.len);
+                    try self.addDbgInfoTypeReloc(ty); // DW.AT.type,  DW.FORM.ref4
+                    dbg_info.appendSliceAssumeCapacity(name_with_null); // DW.AT.name, DW.FORM.string
+
+                },
+
+                else => unreachable, // not a valid function parameter
+            }
+        },
+        .plan9 => {},
+        .none => {},
+    }
+}
+
 fn airBreakpoint(self: *Self) !void {
     _ = try self.addInst(.{
         .tag = .interrupt,
@@ -4424,7 +4428,7 @@ fn airDbgVar(self: *Self, inst: Air.Inst.Index) !void {
 }
 
 fn genVarDbgInfo(
-    self: *Self,
+    self: Self,
     tag: Air.Inst.Tag,
     ty: Type,
     mcv: MCValue,
@@ -4445,17 +4449,23 @@ fn genVarDbgInfo(
                         reg.dwarfLocOp(),
                     });
                 },
-                .ptr_stack_offset, .stack_offset => |off| {
+
+                .ptr_stack_offset,
+                .stack_offset,
+                => |off| {
                     try dbg_info.ensureUnusedCapacity(7);
                     const fixup = dbg_info.items.len;
                     dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
                         1, // we will backpatch it after we encode the displacement in LEB128
-                        DW.OP.breg6, // .rbp TODO handle -fomit-frame-pointer
+                        Register.rbp.dwarfLocOpDeref(), // TODO handle -fomit-frame-pointer
                     });
                     leb128.writeILEB128(dbg_info.writer(), -off) catch unreachable;
                     dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
                 },
-                .memory, .linker_load => {
+
+                .memory,
+                .linker_load,
+                => {
                     const ptr_width = @intCast(u8, @divExact(self.target.cpu.arch.ptrBitWidth(), 8));
                     const is_ptr = switch (tag) {
                         .dbg_var_ptr => true,
@@ -4494,27 +4504,23 @@ fn genVarDbgInfo(
                         else => {},
                     }
                 },
+
                 .immediate => |x| {
-                    const signedness: std.builtin.Signedness = blk: {
-                        if (ty.zigTypeTag() != .Int) break :blk .unsigned;
-                        break :blk ty.intInfo(self.target.*).signedness;
-                    };
                     try dbg_info.ensureUnusedCapacity(2);
                     const fixup = dbg_info.items.len;
                     dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
                         1,
-                        switch (signedness) {
-                            .signed => DW.OP.consts,
-                            .unsigned => DW.OP.constu,
-                        },
+                        if (ty.isSignedInt()) DW.OP.consts else DW.OP.constu,
                     });
-                    switch (signedness) {
-                        .signed => try leb128.writeILEB128(dbg_info.writer(), @bitCast(i64, x)),
-                        .unsigned => try leb128.writeULEB128(dbg_info.writer(), x),
+                    if (ty.isSignedInt()) {
+                        try leb128.writeILEB128(dbg_info.writer(), @bitCast(i64, x));
+                    } else {
+                        try leb128.writeULEB128(dbg_info.writer(), x);
                     }
                     try dbg_info.append(DW.OP.stack_value);
                     dbg_info.items[fixup] += @intCast(u8, dbg_info.items.len - fixup - 2);
                 },
+
                 .undef => {
                     // DW.AT.location, DW.FORM.exprloc
                     // uleb128(exprloc_len)
@@ -4530,12 +4536,14 @@ fn genVarDbgInfo(
                     dbg_info.appendSliceAssumeCapacity(implicit_value_len.items);
                     dbg_info.appendNTimesAssumeCapacity(0xaa, abi_size);
                 },
+
                 .none => {
                     try dbg_info.ensureUnusedCapacity(3);
                     dbg_info.appendSliceAssumeCapacity(&[3]u8{ // DW.AT.location, DW.FORM.exprloc
                         2, DW.OP.lit0, DW.OP.stack_value,
                     });
                 },
+
                 else => {
                     try dbg_info.ensureUnusedCapacity(2);
                     dbg_info.appendSliceAssumeCapacity(&[2]u8{ // DW.AT.location, DW.FORM.exprloc
@@ -4556,7 +4564,7 @@ fn genVarDbgInfo(
 
 /// Adds a Type to the .debug_info at the current position. The bytes will be populated later,
 /// after codegen for this symbol is done.
-fn addDbgInfoTypeReloc(self: *Self, ty: Type) !void {
+fn addDbgInfoTypeReloc(self: Self, ty: Type) !void {
     switch (self.debug_output) {
         .dwarf => |dw| {
             const dbg_info = &dw.dbg_info;

src/arch/x86_64/bits.zig

@@ -135,8 +135,6 @@ pub const Condition = enum(u5) {
     }
 };
 
-// zig fmt: off
-
 /// Definitions of all of the general purpose x64 registers. The order is semantically meaningful.
 /// The registers are defined such that IDs go in descending order of 64-bit,
 /// 32-bit, 16-bit, and then 8-bit, and each set contains exactly sixteen
@@ -152,6 +150,7 @@ pub const Condition = enum(u5) {
 /// The ID can be easily determined by figuring out what range the register is
 /// in, and then subtracting the base.
 pub const Register = enum(u7) {
+    // zig fmt: off
     // 0 through 15, 64-bit registers. 8-15 are extended.
     // id is just the int value.
     rax, rcx, rdx, rbx, rsp, rbp, rsi, rdi,
@@ -184,6 +183,7 @@ pub const Register = enum(u7) {
 
     // Pseudo-value for MIR instructions.
     none,
+    // zig fmt: on
 
     pub fn id(self: Register) u7 {
         return switch (@enumToInt(self)) {
@@ -258,27 +258,66 @@ pub const Register = enum(u7) {
     }
 
     pub fn dwarfLocOp(self: Register) u8 {
-        return switch (self.to64()) {
-            .rax => DW.OP.reg0,
-            .rdx => DW.OP.reg1,
-            .rcx => DW.OP.reg2,
-            .rbx => DW.OP.reg3,
-            .rsi => DW.OP.reg4,
-            .rdi => DW.OP.reg5,
-            .rbp => DW.OP.reg6,
-            .rsp => DW.OP.reg7,
+        switch (@enumToInt(self)) {
+            0...63 => return switch (self.to64()) {
+                .rax => DW.OP.reg0,
+                .rdx => DW.OP.reg1,
+                .rcx => DW.OP.reg2,
+                .rbx => DW.OP.reg3,
+                .rsi => DW.OP.reg4,
+                .rdi => DW.OP.reg5,
+                .rbp => DW.OP.reg6,
+                .rsp => DW.OP.reg7,
 
-            .r8 => DW.OP.reg8,
-            .r9 => DW.OP.reg9,
-            .r10 => DW.OP.reg10,
-            .r11 => DW.OP.reg11,
-            .r12 => DW.OP.reg12,
-            .r13 => DW.OP.reg13,
-            .r14 => DW.OP.reg14,
-            .r15 => DW.OP.reg15,
+                .r8 => DW.OP.reg8,
+                .r9 => DW.OP.reg9,
+                .r10 => DW.OP.reg10,
+                .r11 => DW.OP.reg11,
+                .r12 => DW.OP.reg12,
+                .r13 => DW.OP.reg13,
+                .r14 => DW.OP.reg14,
+                .r15 => DW.OP.reg15,
+
+                else => unreachable,
+            },
+
+            64...79 => return @as(u8, self.enc()) + DW.OP.reg17,
 
             else => unreachable,
-        };
+        }
+    }
+
+    /// DWARF encodings that push a value onto the DWARF stack that is either
+    /// the contents of a register or the result of adding the contents a given
+    /// register to a given signed offset.
+    pub fn dwarfLocOpDeref(self: Register) u8 {
+        switch (@enumToInt(self)) {
+            0...63 => return switch (self.to64()) {
+                .rax => DW.OP.breg0,
+                .rdx => DW.OP.breg1,
+                .rcx => DW.OP.breg2,
+                .rbx => DW.OP.breg3,
+                .rsi => DW.OP.breg4,
+                .rdi => DW.OP.breg5,
+                .rbp => DW.OP.breg6,
+                .rsp => DW.OP.fbreg,
+
+                .r8 => DW.OP.breg8,
+                .r9 => DW.OP.breg9,
+                .r10 => DW.OP.breg10,
+                .r11 => DW.OP.breg11,
+                .r12 => DW.OP.breg12,
+                .r13 => DW.OP.breg13,
+                .r14 => DW.OP.breg14,
+                .r15 => DW.OP.breg15,
+
+                else => unreachable,
+            },
+
+            64...79 => return @as(u8, self.enc()) + DW.OP.breg17,
+
+            else => unreachable,
+        }
     }
 };
 

src/link/Dwarf.zig

@@ -405,8 +405,11 @@ pub const DeclState = struct {
                     const value: u64 = if (values) |vals| value: {
                         if (vals.count() == 0) break :value @intCast(u64, field_i); // auto-numbered
                         const value = vals.keys()[field_i];
+                        // TODO do not assume a 64bit enum value - could be bigger.
+                        // See https://github.com/ziglang/zig/issues/645
                         var int_buffer: Value.Payload.U64 = undefined;
-                        break :value value.enumToInt(ty, &int_buffer).toUnsignedInt(target);
+                        const field_int_val = value.enumToInt(ty, &int_buffer);
+                        break :value @bitCast(u64, field_int_val.toSignedInt());
                     } else @intCast(u64, field_i);
                     mem.writeInt(u64, dbg_info_buffer.addManyAsArrayAssumeCapacity(8), value, target_endian);
                 }

src/link/MachO.zig

@@ -329,8 +329,7 @@ pub fn openPath(allocator: Allocator, options: link.Options) !*MachO {
 
     if (!options.strip and options.module != null) {
         // Create dSYM bundle.
-        const dir = options.module.?.zig_cache_artifact_directory;
-        log.debug("creating {s}.dSYM bundle in {?s}", .{ emit.sub_path, dir.path });
+        log.debug("creating {s}.dSYM bundle", .{emit.sub_path});
 
         const d_sym_path = try fmt.allocPrint(
             allocator,
@@ -339,7 +338,7 @@ pub fn openPath(allocator: Allocator, options: link.Options) !*MachO {
         );
         defer allocator.free(d_sym_path);
 
-        var d_sym_bundle = try dir.handle.makeOpenPath(d_sym_path, .{});
+        var d_sym_bundle = try emit.directory.handle.makeOpenPath(d_sym_path, .{});
         defer d_sym_bundle.close();
 
         const d_sym_file = try d_sym_bundle.createFile(emit.sub_path, .{

test/behavior/enum.zig

@@ -1146,8 +1146,6 @@ test "size of enum with only one tag which has explicit integer tag type" {
 }
 
 test "switch on an extern enum with negative value" {
-    // TODO x86, wasm backends fail because they assume that enum tag types are unsigned
-    if (@import("builtin").zig_backend == .stage2_x86_64) return error.SkipZigTest;
     if (@import("builtin").zig_backend == .stage2_wasm) return error.SkipZigTest;
 
     const Foo = enum(c_int) {