compile time string hashing and assembly comparison

hashstr.cpp

#include <iostream>

constexpr unsigned _hash_string_recursive(unsigned hash, const char* str)
{
    return ( !*str ? hash :
    _hash_string_recursive(((hash << 5) + hash) + *str, str + 1));
}

constexpr unsigned hash_string(const char* str)
{
    return ( !str ? 0 :
    _hash_string_recursive(5381, str));
}

class HashedString
{
public:
    inline explicit constexpr HashedString(const char* str);

    inline constexpr bool operator==(const HashedString& other) const;
    inline constexpr bool operator!=(const HashedString& other) const;
    inline constexpr bool operator<(const HashedString& other) const;

    unsigned hash;
};


constexpr HashedString::HashedString(const char* str):
hash(hash_string(str))
{
}

bool constexpr HashedString::operator==(const HashedString& other) const
{
    return hash == other.hash;
}

bool constexpr HashedString::operator!=(const HashedString& other) const
{
    return hash != other.hash;
}

bool constexpr HashedString::operator<(const HashedString& other) const
{
    return hash < other.hash;
}

static_assert(HashedString("foo") != HashedString("bar"), "compare different hashed string by key");
static_assert(HashedString("foo") == HashedString("foo"), "compare identical strings by key");
static_assert(HashedString("bar") < HashedString("foo"), "compare strings by key ordering");

int main()
{
	HashedString foo("foo");
	HashedString bar("bar");

	std::string s;
	std::cin >> s;
	HashedString rtimehash(s.c_str());

	if (foo == rtimehash)
	{
		std::cout << "foo" << std::endl;
		std::cout << foo.hash << std::endl;
	}
	else if (bar == rtimehash)
	{
		std::cout << "bar" << std::endl;
		std::cout << foo.hash << std::endl;
	}
}

hashstr.s

	.file	"hashstr.cpp"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"foo"
.LC1:
	.string	"bar"
	.section	.text.startup,"ax",@progbits
	.p2align 4,,15
	.globl	main
	.type	main, @function
main:
.LFB1283:
	.cfi_startproc
	.cfi_personality 0,__gxx_personality_v0
	.cfi_lsda 0,.LLSDA1283
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	pushl	%esi
	pushl	%ebx
	andl	$-16, %esp
	subl	$32, %esp
	leal	28(%esp), %ebx
	.cfi_offset 3, -16
	.cfi_offset 6, -12
	movl	$_ZNSs4_Rep20_S_empty_rep_storageE+12, 28(%esp)
	movl	%ebx, 4(%esp)
	movl	$_ZSt3cin, (%esp)
.LEHB0:
	call	_ZStrsIcSt11char_traitsIcESaIcEERSt13basic_istreamIT_T0_ES7_RSbIS4_S5_T1_E
	movl	28(%esp), %eax
	testl	%eax, %eax
	je	.L4
	movzbl	(%eax), %ecx
	testb	%cl, %cl
	je	.L4
	movl	$5381, %edx
	.p2align 4,,7
	.p2align 3
.L5:
	movl	%edx, %esi
	movsbl	%cl, %ecx
	sall	$5, %esi
	addl	$1, %eax
	addl	%esi, %ecx
	addl	%ecx, %edx
	movzbl	(%eax), %ecx
	testb	%cl, %cl
	jne	.L5
	cmpl	$193491849, %edx
	je	.L17
	cmpl	$193487034, %edx
	je	.L18
.L4:
	movl	%ebx, (%esp)
	call	_ZNSsD1Ev
	leal	-8(%ebp), %esp
	xorl	%eax, %eax
	popl	%ebx
	.cfi_remember_state
	.cfi_restore 3
	popl	%esi
	.cfi_restore 6
	popl	%ebp
	.cfi_def_cfa 4, 4
	.cfi_restore 5
	ret
.L18:
	.cfi_restore_state
	movl	$.LC1, 4(%esp)
	movl	$_ZSt4cout, (%esp)
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
.L15:
	movl	%eax, (%esp)
	call	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_
	movl	$193491849, 4(%esp)
	movl	$_ZSt4cout, (%esp)
	call	_ZNSo9_M_insertImEERSoT_
	movl	%eax, (%esp)
	call	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_
	jmp	.L4
.L17:
	movl	$.LC0, 4(%esp)
	movl	$_ZSt4cout, (%esp)
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
.LEHE0:
	jmp	.L15
.L8:
	movl	%eax, %esi
	movl	%ebx, (%esp)
	call	_ZNSsD1Ev
	movl	%esi, (%esp)
.LEHB1:
	call	_Unwind_Resume
.LEHE1:
	.cfi_endproc
.LFE1283:
	.globl	__gxx_personality_v0
	.section	.gcc_except_table,"a",@progbits
.LLSDA1283:
	.byte	0xff
	.byte	0xff
	.byte	0x1
	.uleb128 .LLSDACSE1283-.LLSDACSB1283
.LLSDACSB1283:
	.uleb128 .LEHB0-.LFB1283
	.uleb128 .LEHE0-.LEHB0
	.uleb128 .L8-.LFB1283
	.uleb128 0
	.uleb128 .LEHB1-.LFB1283
	.uleb128 .LEHE1-.LEHB1
	.uleb128 0
	.uleb128 0
.LLSDACSE1283:
	.section	.text.startup
	.size	main, .-main
	.p2align 4,,15
	.type	_GLOBAL__sub_I_main, @function
_GLOBAL__sub_I_main:
.LFB1443:
	.cfi_startproc
	subl	$28, %esp
	.cfi_def_cfa_offset 32
	movl	$_ZStL8__ioinit, (%esp)
	call	_ZNSt8ios_base4InitC1Ev
	movl	$__dso_handle, 8(%esp)
	movl	$_ZStL8__ioinit, 4(%esp)
	movl	$_ZNSt8ios_base4InitD1Ev, (%esp)
	call	__cxa_atexit
	addl	$28, %esp
	.cfi_def_cfa_offset 4
	ret
	.cfi_endproc
.LFE1443:
	.size	_GLOBAL__sub_I_main, .-_GLOBAL__sub_I_main
	.section	.ctors,"aw",@progbits
	.align 4
	.long	_GLOBAL__sub_I_main
	.local	_ZStL8__ioinit
	.comm	_ZStL8__ioinit,1,1
	.weakref	_ZL20__gthrw_pthread_oncePiPFvvE,pthread_once
	.weakref	_ZL27__gthrw_pthread_getspecificj,pthread_getspecific
	.weakref	_ZL27__gthrw_pthread_setspecificjPKv,pthread_setspecific
	.weakref	_ZL22__gthrw_pthread_createPmPK14pthread_attr_tPFPvS3_ES3_,pthread_create
	.weakref	_ZL20__gthrw_pthread_joinmPPv,pthread_join
	.weakref	_ZL21__gthrw_pthread_equalmm,pthread_equal
	.weakref	_ZL20__gthrw_pthread_selfv,pthread_self
	.weakref	_ZL22__gthrw_pthread_detachm,pthread_detach
	.weakref	_ZL22__gthrw_pthread_cancelm,pthread_cancel
	.weakref	_ZL19__gthrw_sched_yieldv,sched_yield
	.weakref	_ZL26__gthrw_pthread_mutex_lockP15pthread_mutex_t,pthread_mutex_lock
	.weakref	_ZL29__gthrw_pthread_mutex_trylockP15pthread_mutex_t,pthread_mutex_trylock
	.weakref	_ZL31__gthrw_pthread_mutex_timedlockP15pthread_mutex_tPK8timespec,pthread_mutex_timedlock
	.weakref	_ZL28__gthrw_pthread_mutex_unlockP15pthread_mutex_t,pthread_mutex_unlock
	.weakref	_ZL26__gthrw_pthread_mutex_initP15pthread_mutex_tPK19pthread_mutexattr_t,pthread_mutex_init
	.weakref	_ZL29__gthrw_pthread_mutex_destroyP15pthread_mutex_t,pthread_mutex_destroy
	.weakref	_ZL30__gthrw_pthread_cond_broadcastP14pthread_cond_t,pthread_cond_broadcast
	.weakref	_ZL27__gthrw_pthread_cond_signalP14pthread_cond_t,pthread_cond_signal
	.weakref	_ZL25__gthrw_pthread_cond_waitP14pthread_cond_tP15pthread_mutex_t,pthread_cond_wait
	.weakref	_ZL30__gthrw_pthread_cond_timedwaitP14pthread_cond_tP15pthread_mutex_tPK8timespec,pthread_cond_timedwait
	.weakref	_ZL28__gthrw_pthread_cond_destroyP14pthread_cond_t,pthread_cond_destroy
	.weakref	_ZL26__gthrw_pthread_key_createPjPFvPvE,pthread_key_create
	.weakref	_ZL26__gthrw_pthread_key_deletej,pthread_key_delete
	.weakref	_ZL30__gthrw_pthread_mutexattr_initP19pthread_mutexattr_t,pthread_mutexattr_init
	.weakref	_ZL33__gthrw_pthread_mutexattr_settypeP19pthread_mutexattr_ti,pthread_mutexattr_settype
	.weakref	_ZL33__gthrw_pthread_mutexattr_destroyP19pthread_mutexattr_t,pthread_mutexattr_destroy
	.ident	"GCC: (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3"
	.section	.note.GNU-stack,"",@progbits