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| author | Jakub Konka <kubkon@jakubkonka.com> | 2020-11-24 18:46:43 +0100 |
|---|---|---|
| committer | Jakub Konka <kubkon@jakubkonka.com> | 2020-11-26 11:50:09 +0100 |
| commit | ef5132c508f89ed8392143f6e8d03e8a2f121ba9 (patch) | |
| tree | 350ef2bf4e2a78e2a4ba3c33c644c164d16e88c7 /src/codegen.zig | |
| parent | 80b1041c21599f5d444373dd35eafe2dc68e3887 (diff) | |
| download | zig-ef5132c508f89ed8392143f6e8d03e8a2f121ba9.tar.gz zig-ef5132c508f89ed8392143f6e8d03e8a2f121ba9.zip | |
stage2 macho: first, rough draft at trampolining
Diffstat (limited to 'src/codegen.zig')
| -rw-r--r-- | src/codegen.zig | 63 |
1 files changed, 45 insertions, 18 deletions
diff --git a/src/codegen.zig b/src/codegen.zig index 6cef7d8d0a..85b039069a 100644 --- a/src/codegen.zig +++ b/src/codegen.zig @@ -2767,24 +2767,51 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type { // For MachO, the binary, with the exception of object files, has to be a PIE. // Therefore, we cannot load an absolute address. assert(x > math.maxInt(u32)); // 32bit direct addressing is not supported by MachO. - // The plan here is to use RIP-relative addressing, but leaving the actual displacement - // information empty (0-padded) and fixing it up later in the linker. - try self.mod_fn.owner_decl.link.macho.addRipPosition(self.bin_file.allocator, .{ - .address = x, - .start = self.code.items.len, - .len = 7, - }); - try self.code.ensureCapacity(self.code.items.len + 9); - // leaq %r, [rip + disp] - self.code.appendSliceAssumeCapacity(&[_]u8{ - 0x48, - 0x8d, - 0x05 | (@as(u8, reg.id() & 0b111) << 3), // R - 0x0, - 0x0, - 0x0, - 0x0, - }); + // The plan here is to use unconditional relative jump to GOT entry, where we store + // pre-calculated and stored effective address to load into the target register. + // We leave the actual displacement information empty (0-padded) and fixing it up + // later in the linker. + if (reg.id() == 0) { // %rax is special-cased + try self.code.ensureCapacity(self.code.items.len + 5); + try self.mod_fn.owner_decl.link.macho.addRipPosition(self.bin_file.allocator, .{ + .address = x, + .start = self.code.items.len, + .len = 5, + }); + // call [label] + self.code.appendSliceAssumeCapacity(&[_]u8{ + 0xE8, + 0x0, + 0x0, + 0x0, + 0x0, + }); + } else { + try self.code.ensureCapacity(self.code.items.len + 10); + // push %rax + self.code.appendSliceAssumeCapacity(&[_]u8{0x50}); + try self.mod_fn.owner_decl.link.macho.addRipPosition(self.bin_file.allocator, .{ + .address = x, + .start = self.code.items.len, + .len = 5, + }); + // call [label] + self.code.appendSliceAssumeCapacity(&[_]u8{ + 0xE8, + 0x0, + 0x0, + 0x0, + 0x0, + }); + // mov %r, %rax + self.code.appendSliceAssumeCapacity(&[_]u8{ + 0x48, + 0x89, + 0xC0 | @as(u8, reg.id()), + }); + // pop %rax + self.code.appendSliceAssumeCapacity(&[_]u8{0x58}); + } } else if (x <= math.maxInt(u32)) { // Moving from memory to a register is a variant of `8B /r`. // Since we're using 64-bit moves, we require a REX. |