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x64: handle storing non-pow2 values to stack from register

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This actually requires storing and shifting mechanics so that we
don't accidentally clobber anything else on the stack.
This commit is contained in:
Jakub Konka
2022-02-16 22:41:19 +01:00
parent 94474ec7c7
commit c1fb14c51e
1 changed files with 48 additions and 9 deletions
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57
src/arch/x86_64/CodeGen.zig
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@@ -3715,15 +3715,54 @@ fn genSetStack(self: *Self, ty: Type, stack_offset: i32, mcv: MCValue) InnerErro
if (stack_offset > math.maxInt(i32)) {
return self.fail("stack offset too large", .{});
}
_ = try self.addInst(.{
.tag = .mov,
.ops = (Mir.Ops{
.reg1 = .rbp,
.reg2 = registerAlias(reg, @intCast(u32, abi_size)),
.flags = 0b10,
}).encode(),
.data = .{ .imm = @bitCast(u32, -stack_offset) },
});
const is_power_of_two = (abi_size % 2) == 0;
if (!is_power_of_two) {
self.register_manager.freezeRegs(&.{reg});
defer self.register_manager.unfreezeRegs(&.{reg});
const tmp_reg = try self.copyToTmpRegister(ty, mcv);
var next_offset = stack_offset;
var remainder = abi_size;
while (remainder > 0) {
const closest_power_of_two = @as(u6, 1) << @intCast(u3, math.log2(remainder));
_ = try self.addInst(.{
.tag = .mov,
.ops = (Mir.Ops{
.reg1 = .rbp,
.reg2 = registerAlias(tmp_reg, closest_power_of_two),
.flags = 0b10,
}).encode(),
.data = .{ .imm = @bitCast(u32, -next_offset) },
});
if (closest_power_of_two > 1) {
_ = try self.addInst(.{
.tag = .shr,
.ops = (Mir.Ops{
.reg1 = tmp_reg,
.flags = 0b10,
}).encode(),
.data = .{ .imm = closest_power_of_two * 8 },
});
}
remainder -= closest_power_of_two;
next_offset -= closest_power_of_two;
}
} else {
_ = try self.addInst(.{
.tag = .mov,
.ops = (Mir.Ops{
.reg1 = .rbp,
.reg2 = registerAlias(reg, @intCast(u32, abi_size)),
.flags = 0b10,
}).encode(),
.data = .{ .imm = @bitCast(u32, -stack_offset) },
});
}
},
.memory,
.embedded_in_code,