codegen: lower field_ptr to memory across linking backends

This requires generating an addend for the target relocation as
the field pointer might point at a field inner to the container.

4 files changed, 40 insertions, 25 deletions

diff --git a/src/link/Coff.zig b/src/link/Coff.zig
index 3ee34682e9..3293cf2dfc 100644
--- a/src/link/Coff.zig
+++ b/src/link/Coff.zig
@@ -724,10 +724,12 @@ pub fn updateDecl(self: *Coff, module: *Module, decl: *Module.Decl) !void {
     var code_buffer = std.ArrayList(u8).init(self.base.allocator);
     defer code_buffer.deinit();
 
-    const res = try codegen.generateSymbol(&self.base, 0, decl.srcLoc(), .{
+    const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
         .ty = decl.ty,
         .val = decl.val,
-    }, &code_buffer, .none);
+    }, &code_buffer, .none, .{
+        .parent_atom_index = 0,
+    });
     const code = switch (res) {
         .externally_managed => |x| x,
         .appended => code_buffer.items,
@@ -1463,9 +1465,8 @@ fn findLib(self: *Coff, arena: Allocator, name: []const u8) !?[]const u8 {
     return null;
 }
 
-pub fn getDeclVAddr(self: *Coff, decl: *const Module.Decl, parent_atom_index: u32, offset: u64) !u64 {
-    _ = parent_atom_index;
-    _ = offset;
+pub fn getDeclVAddr(self: *Coff, decl: *const Module.Decl, reloc_info: link.File.RelocInfo) !u64 {
+    _ = reloc_info;
     assert(self.llvm_object == null);
     return self.text_section_virtual_address + decl.link.coff.text_offset;
 }
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index 2b063dd1d2..1424a521b9 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -188,6 +188,7 @@ relocs: RelocTable = .{},
 const Reloc = struct {
     target: u32,
     offset: u64,
+    addend: u32,
     prev_vaddr: u64,
 };
 
@@ -421,20 +422,21 @@ pub fn deinit(self: *Elf) void {
     self.atom_by_index_table.deinit(self.base.allocator);
 }
 
-pub fn getDeclVAddr(self: *Elf, decl: *const Module.Decl, parent_atom_index: u32, offset: u64) !u64 {
+pub fn getDeclVAddr(self: *Elf, decl: *const Module.Decl, reloc_info: File.RelocInfo) !u64 {
     assert(self.llvm_object == null);
     assert(decl.link.elf.local_sym_index != 0);
 
     const target = decl.link.elf.local_sym_index;
     const vaddr = self.local_symbols.items[target].st_value;
-    const atom = self.atom_by_index_table.get(parent_atom_index).?;
+    const atom = self.atom_by_index_table.get(reloc_info.parent_atom_index).?;
     const gop = try self.relocs.getOrPut(self.base.allocator, atom);
     if (!gop.found_existing) {
         gop.value_ptr.* = .{};
     }
     try gop.value_ptr.append(self.base.allocator, .{
         .target = target,
-        .offset = offset,
+        .offset = reloc_info.offset,
+        .addend = reloc_info.addend,
         .prev_vaddr = vaddr,
     });
 
@@ -1039,7 +1041,7 @@ pub fn flushModule(self: *Elf, comp: *Compilation) !void {
 
             for (relocs.items) |*reloc| {
                 const target_sym = self.local_symbols.items[reloc.target];
-                const target_vaddr = target_sym.st_value;
+                const target_vaddr = target_sym.st_value + reloc.addend;
 
                 if (target_vaddr == reloc.prev_vaddr) continue;
 
@@ -3074,7 +3076,7 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
 
     // TODO implement .debug_info for global variables
     const decl_val = if (decl.val.castTag(.variable)) |payload| payload.data.init else decl.val;
-    const res = try codegen.generateSymbol(&self.base, decl.link.elf.local_sym_index, decl.srcLoc(), .{
+    const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
         .ty = decl.ty,
         .val = decl_val,
     }, &code_buffer, .{
@@ -3083,6 +3085,8 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
             .dbg_info = &dbg_info_buffer,
             .dbg_info_type_relocs = &dbg_info_type_relocs,
         },
+    }, .{
+        .parent_atom_index = decl.link.elf.local_sym_index,
     });
     const code = switch (res) {
         .externally_managed => |x| x,
@@ -3130,8 +3134,10 @@ pub fn lowerUnnamedConst(self: *Elf, typed_value: TypedValue, decl: *Module.Decl
     atom.local_sym_index = try self.allocateLocalSymbol();
     try self.atom_by_index_table.putNoClobber(self.base.allocator, atom.local_sym_index, atom);
 
-    const res = try codegen.generateSymbol(&self.base, atom.local_sym_index, decl.srcLoc(), typed_value, &code_buffer, .{
+    const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), typed_value, &code_buffer, .{
         .none = .{},
+    }, .{
+        .parent_atom_index = atom.local_sym_index,
     });
     const code = switch (res) {
         .externally_managed => |x| x,
diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 9f038d9b9f..2f55c69b3a 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -3781,8 +3781,10 @@ pub fn lowerUnnamedConst(self: *MachO, typed_value: TypedValue, decl: *Module.De
     const atom = try self.createEmptyAtom(local_sym_index, @sizeOf(u64), math.log2(required_alignment));
     try self.atom_by_index_table.putNoClobber(self.base.allocator, local_sym_index, atom);
 
-    const res = try codegen.generateSymbol(&self.base, local_sym_index, decl.srcLoc(), typed_value, &code_buffer, .{
+    const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), typed_value, &code_buffer, .{
         .none = .{},
+    }, .{
+        .parent_atom_index = local_sym_index,
     });
     const code = switch (res) {
         .externally_managed => |x| x,
@@ -3790,6 +3792,7 @@ pub fn lowerUnnamedConst(self: *MachO, typed_value: TypedValue, decl: *Module.De
         .fail => |em| {
             decl.analysis = .codegen_failure;
             try module.failed_decls.put(module.gpa, decl, em);
+            log.err("{s}", .{em.msg});
             return error.AnalysisFail;
         },
     };
@@ -3860,7 +3863,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
 
     const decl_val = if (decl.val.castTag(.variable)) |payload| payload.data.init else decl.val;
     const res = if (debug_buffers) |dbg|
-        try codegen.generateSymbol(&self.base, decl.link.macho.local_sym_index, decl.srcLoc(), .{
+        try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
             .ty = decl.ty,
             .val = decl_val,
         }, &code_buffer, .{
@@ -3869,12 +3872,16 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
                 .dbg_info = &dbg.dbg_info_buffer,
                 .dbg_info_type_relocs = &dbg.dbg_info_type_relocs,
             },
+        }, .{
+            .parent_atom_index = decl.link.macho.local_sym_index,
         })
     else
-        try codegen.generateSymbol(&self.base, decl.link.macho.local_sym_index, decl.srcLoc(), .{
+        try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
             .ty = decl.ty,
             .val = decl_val,
-        }, &code_buffer, .none);
+        }, &code_buffer, .none, .{
+            .parent_atom_index = decl.link.macho.local_sym_index,
+        });
 
     const code = blk: {
         switch (res) {
@@ -4357,15 +4364,15 @@ pub fn freeDecl(self: *MachO, decl: *Module.Decl) void {
     }
 }
 
-pub fn getDeclVAddr(self: *MachO, decl: *const Module.Decl, parent_atom_index: u32, offset: u64) !u64 {
+pub fn getDeclVAddr(self: *MachO, decl: *const Module.Decl, reloc_info: File.RelocInfo) !u64 {
     assert(self.llvm_object == null);
     assert(decl.link.macho.local_sym_index != 0);
 
-    const atom = self.atom_by_index_table.get(parent_atom_index).?;
+    const atom = self.atom_by_index_table.get(reloc_info.parent_atom_index).?;
     try atom.relocs.append(self.base.allocator, .{
-        .offset = @intCast(u32, offset),
+        .offset = @intCast(u32, reloc_info.offset),
         .target = .{ .local = decl.link.macho.local_sym_index },
-        .addend = 0,
+        .addend = reloc_info.addend,
         .subtractor = null,
         .pcrel = false,
         .length = 3,
@@ -4375,7 +4382,7 @@ pub fn getDeclVAddr(self: *MachO, decl: *const Module.Decl, parent_atom_index: u
             else => unreachable,
         },
     });
-    try atom.rebases.append(self.base.allocator, offset);
+    try atom.rebases.append(self.base.allocator, reloc_info.offset);
 
     return 0;
 }
diff --git a/src/link/Plan9.zig b/src/link/Plan9.zig
index 4648a6a673..8096b2d38c 100644
--- a/src/link/Plan9.zig
+++ b/src/link/Plan9.zig
@@ -304,10 +304,12 @@ pub fn updateDecl(self: *Plan9, module: *Module, decl: *Module.Decl) !void {
     const decl_val = if (decl.val.castTag(.variable)) |payload| payload.data.init else decl.val;
     // TODO we need the symbol index for symbol in the table of locals for the containing atom
     const sym_index = decl.link.plan9.sym_index orelse 0;
-    const res = try codegen.generateSymbol(&self.base, @intCast(u32, sym_index), decl.srcLoc(), .{
+    const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
         .ty = decl.ty,
         .val = decl_val,
-    }, &code_buffer, .{ .none = .{} });
+    }, &code_buffer, .{ .none = .{} }, .{
+        .parent_atom_index = @intCast(u32, sym_index),
+    });
     const code = switch (res) {
         .externally_managed => |x| x,
         .appended => code_buffer.items,
@@ -752,9 +754,8 @@ pub fn allocateDeclIndexes(self: *Plan9, decl: *Module.Decl) !void {
     _ = self;
     _ = decl;
 }
-pub fn getDeclVAddr(self: *Plan9, decl: *const Module.Decl, parent_atom_index: u32, offset: u64) !u64 {
-    _ = parent_atom_index;
-    _ = offset;
+pub fn getDeclVAddr(self: *Plan9, decl: *const Module.Decl, reloc_info: link.File.RelocInfo) !u64 {
+    _ = reloc_info;
     if (decl.ty.zigTypeTag() == .Fn) {
         var start = self.bases.text;
         var it_file = self.fn_decl_table.iterator();