Commit c73eb00727

@@ -780,6 +780,8 @@ fn airArg(self: *Self, inst: Air.Inst.Index) !void {
     // TODO Copy registers to the stack
     const mcv = result;
 
+    try self.genArgDbgInfo(inst, mcv, @intCast(u32, arg_index));
+
     if (self.liveness.isUnused(inst))
         return self.finishAirBookkeeping();
 
@@ -1038,6 +1040,26 @@ fn airSwitch(self: *Self, inst: Air.Inst.Index) !void {
 
 // Common helper functions
 
+/// 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 {
+    switch (self.debug_output) {
+        .dwarf => |dw| {
+            assert(ty.hasRuntimeBits());
+            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 atom = switch (self.bin_file.tag) {
+                .elf => &mod.declPtr(self.mod_fn.owner_decl).link.elf.dbg_info_atom,
+                else => unreachable,
+            };
+            try dw.addTypeReloc(atom, ty, @intCast(u32, index), null);
+        },
+        else => {},
+    }
+}
+
 fn addInst(self: *Self, inst: Mir.Inst) error{OutOfMemory}!Mir.Inst.Index {
     const gpa = self.gpa;
     try self.mir_instructions.ensureUnusedCapacity(gpa, 1);
@@ -1166,6 +1188,40 @@ fn finishAir(self: *Self, inst: Air.Inst.Index, result: MCValue, operands: [Live
     self.finishAirBookkeeping();
 }
 
+fn genArgDbgInfo(self: *Self, inst: Air.Inst.Index, mcv: MCValue, arg_index: u32) !void {
+    const ty = self.air.instructions.items(.data)[inst].ty;
+    const name = self.mod_fn.getParamName(arg_index);
+    const name_with_null = name.ptr[0 .. name.len + 1];
+
+    switch (mcv) {
+        .register => |reg| {
+            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
+                },
+                else => {},
+            }
+        },
+        .stack_offset => |offset| {
+            _ = offset;
+            switch (self.debug_output) {
+                .dwarf => {},
+                else => {},
+            }
+        },
+        else => {},
+    }
+}
+
 fn genLoad(self: *Self, value_reg: Register, addr_reg: Register, comptime off_type: type, off: off_type, abi_size: u64) !void {
     assert(off_type == Register or off_type == i13);