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need to go through the GOT, and use a temporary register

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mparadinha 2022-02-02 08:48:00 +00:00
parent b67b89025c
commit ef4c54ba38
1 changed files with 57 additions and 5 deletions
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62
src/arch/x86_64/CodeGen.zig
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@ -1781,18 +1781,70 @@ fn store(self: *Self, ptr: MCValue, value: MCValue, ptr_ty: Type, value_ty: Type
}
},
.memory => |addr| {
const reg = try self.copyToTmpRegister(ptr_ty, .{ .memory = addr });
// TODO: in case the address fits in an imm32 we can use [ds:imm32]
// instead of wasting an instruction copying the address to a register
const addr_reg = try self.copyToTmpRegister(ptr_ty, .{ .immediate = addr });
// to get the actual address of the value we want to modify we have to go through the GOT
// mov reg, [reg]
_ = try self.addInst(.{
.tag = .mov,
.ops = (Mir.Ops{
.reg1 = reg.to64(),
.reg2 = reg.to64(),
.flags = 0b10,
.reg1 = addr_reg.to64(),
.reg2 = addr_reg.to64(),
.flags = 0b01,
}).encode(),
.data = .{ .imm = 0 },
});
return self.store(.{ .register = reg }, value, ptr_ty, value_ty);
const abi_size = value_ty.abiSize(self.target.*);
switch (value) {
.immediate => |imm| {
const payload = try self.addExtra(Mir.ImmPair{
.dest_off = 0,
.operand = @intCast(u32, imm),
});
_ = try self.addInst(.{
.tag = .mov_mem_imm,
.ops = (Mir.Ops{
.reg1 = addr_reg.to64(),
.flags = switch (abi_size) {
1 => 0b00,
2 => 0b01,
4 => 0b10,
8 => flag: {
const top_bits: u32 = @intCast(u32, imm >> 32);
const can_extend = if (value_ty.isUnsignedInt())
(top_bits == 0) and (imm & 0x8000_0000) == 0
else
top_bits == 0xffff_ffff;
if (!can_extend) {
return self.fail("TODO imm64 would get incorrectly sign extended", .{});
}
break :flag 0b11;
},
else => {
return self.fail("TODO saving imm to memory for abi_size {}", .{abi_size});
},
},
}).encode(),
.data = .{ .payload = payload },
});
},
.register => |reg| {
_ = try self.addInst(.{
.tag = .mov,
.ops = (Mir.Ops{
.reg1 = addr_reg.to64(),
.reg2 = reg,
.flags = 0b10,
}).encode(),
.data = .{ .imm = 0 },
});
},
else => return self.fail("TODO implement storing {} to MCValue.memory", .{value}),
}
},
.stack_offset => {
return self.fail("TODO implement storing to MCValue.stack_offset", .{});