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Přemysl Eric Janouch
2016-12-22 22:58:20 +01:00
commit 128fb157b3
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14
interpreters/Makefile Normal file
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CC = c99
CFLAGS = -O3
NAMES = bf bf-faster-loops bf-optimizing \
bf-jit bf-jit-opt bf-jit-unsafe bf-jit-unsafe-opt
all: $(NAMES)
%: %.c
$(CC) $(CPPFLAGS) $(CFLAGS) $< -o $@
clean:
rm -f $(NAMES)
.PHONY: all clean

15
interpreters/README.adoc Normal file
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This directory contains several Brainfuck interpreters in various states of
sophistication, from the simplest approach to an optimizing JIT compiler:
* `bf.c` is the stupidest one and the oldest by far
* `bf-faster-loops.c` precomputes loop jumps
* `bf-optimizing.c` improves on that by changing `[-]+` loops into assignments
* `bf-jit.c` adds JIT compilation for Intel x86-64
* `bf-jit-opt.c` tries a bit harder to avoid looping on the current value
* `bf-jit-unsafe.c` abolishes all boundary checks when moving across the tape
* `bf-jit-unsafe-opt.c` makes use of immediate offsets to modify values
I recommend using a tool such as 'meld' to view the differences.
Just run `make` in this directory to have them all built, and append
`CPPFLAGS=-DDEBUG` to get dumps of the IR for the more sophisticated JITs.

151
interpreters/bf-faster-loops.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <assert.h>
#include <errno.h>
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xmalloc (size_t n)
{
void *p = malloc (n);
if (!p)
exit_fatal ("malloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->alloc = 16;
self->len = 0;
self->str = strcpy (xmalloc (self->alloc), "");
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Main --------------------------------------------------------------------
int
main (int argc, char *argv[])
{
struct str program; str_init (&program);
struct str data; str_init (&data);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
FILE *input = fopen ("/dev/tty", "rb");
if (!input)
exit_fatal ("can't open terminal for reading\n");
size_t *pairs = xmalloc (sizeof *pairs * program.len);
size_t *stack = xmalloc (sizeof *stack * program.len);
size_t nesting = 0;
for (size_t i = 0; i < program.len; i++)
{
switch (program.str[i])
{
case '[':
stack[nesting++] = i;
break;
case ']':
assert (nesting > 0);
--nesting;
pairs[stack[nesting]] = i;
pairs[i] = stack[nesting];
}
}
assert (nesting == 0);
size_t dataptr = 0;
str_append_c (&data, 0);
for (size_t i = 0; i < program.len; i++)
{
switch (program.str[i])
{
case '>':
assert (dataptr != SIZE_MAX);
if (++dataptr == data.len)
str_append_c (&data, 0);
break;
case '<':
assert (dataptr != 0);
dataptr--;
break;
case '+': data.str[dataptr]++; break;
case '-': data.str[dataptr]--; break;
case '.':
fputc (data.str[dataptr], stdout);
break;
case ',':
data.str[dataptr] = c = fgetc (input);
assert (c != EOF);
break;
case '[': if (!data.str[dataptr]) i = pairs[i]; break;
case ']': if ( data.str[dataptr]) i = pairs[i]; break;
default:
break;
}
}
return 0;
}

495
interpreters/bf-jit-opt.c Normal file
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// This is an exercise in futility more than anything else
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#if (defined __x86_64__ || defined __amd64__) && defined __unix__
#include <sys/mman.h>
#else
#error Platform not supported
#endif
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xcalloc (size_t m, size_t n)
{
void *p = calloc (m, n);
if (!p)
exit_fatal ("calloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->len = 0;
self->str = xcalloc (1, (self->alloc = 16));
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Application -------------------------------------------------------------
struct str data; ///< Data tape
volatile size_t dataptr; ///< Current location on the tape
FILE *input; ///< User input
enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END,
EAT, INCACC, DECACC };
bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
struct instruction { enum command cmd; size_t arg; };
#define INSTRUCTION(c, a) (struct instruction) { (c), (a) }
// - - Callbacks - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Some things I just really don't want to write in assembly even though it
// is effectively a big performance hit, eliminating the advantage of JIT
static void
right (size_t arg)
{
assert (SIZE_MAX - dataptr > arg);
dataptr += arg;
while (dataptr >= data.len)
str_append_c (&data, 0);
}
static void
left (size_t arg)
{
assert (dataptr >= arg);
dataptr -= arg;
}
static void
cin (void)
{
int c;
data.str[dataptr] = c = fgetc (input);
assert (c != EOF);
}
// - - Main - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#ifdef DEBUG
static void
debug_dump (const char *filename, struct instruction *in, size_t len)
{
FILE *fp = fopen (filename, "w");
long indent = 0;
for (size_t i = 0; i < len; i++)
{
if (in[i].cmd == END)
indent--;
for (long k = 0; k < indent; k++)
fprintf (fp, " ");
switch (in[i].cmd)
{
case RIGHT: fprintf (fp, "RIGHT %zu\n", in[i].arg); break;
case LEFT: fprintf (fp, "LEFT %zu\n", in[i].arg); break;
case INC: fprintf (fp, "INC %zu\n", in[i].arg); break;
case DEC: fprintf (fp, "DEC %zu\n", in[i].arg); break;
case OUT: fprintf (fp, "OUT %zu\n", in[i].arg); break;
case IN: fprintf (fp, "IN %zu\n", in[i].arg); break;
case BEGIN: fprintf (fp, "BEGIN %zu\n", in[i].arg); break;
case END: fprintf (fp, "END %zu\n", in[i].arg); break;
case SET: fprintf (fp, "SET %zu\n", in[i].arg); break;
case EAT: fprintf (fp, "EAT %zu\n", in[i].arg); break;
case INCACC: fprintf (fp, "INCACC %zu\n", in[i].arg); break;
case DECACC: fprintf (fp, "DECACC %zu\n", in[i].arg); break;
}
if (in[i].cmd == BEGIN)
indent++;
}
fclose (fp);
}
#else
#define debug_dump(...)
#endif
int
main (int argc, char *argv[])
{
(void) argc;
(void) argv;
struct str program;
str_init (&program);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
if (!(input = fopen ("/dev/tty", "rb")))
exit_fatal ("can't open terminal for reading\n");
// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct instruction *parsed = xcalloc (sizeof *parsed, program.len);
size_t parsed_len = 0;
for (size_t i = 0; i < program.len; i++)
{
enum command cmd;
switch (program.str[i])
{
case '>': cmd = RIGHT; break;
case '<': cmd = LEFT; break;
case '+': cmd = INC; break;
case '-': cmd = DEC; break;
case '.': cmd = OUT; break;
case ',': cmd = IN; break;
case '[': cmd = BEGIN; break;
case ']': cmd = END; break;
default: continue;
}
// The most basic optimization is to group identical commands together
if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd)
parsed_len++;
parsed[parsed_len - 1].cmd = cmd;
parsed[parsed_len - 1].arg++;
}
// - - Optimization passes - - - - - - - - - - - - - - - - - - - - - - - - - - -
debug_dump ("bf-no-opt.txt", parsed, parsed_len);
size_t in = 0, out = 0;
for (; in < parsed_len; in++, out++)
{
// This shows up in mandelbrot.bf a lot but actually helps hanoi.bf
if (in + 5 < parsed_len
&& parsed[in].cmd == BEGIN && parsed[in + 5].cmd == END
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == LEFT && parsed[in + 4].cmd == RIGHT
&& parsed[in + 2].arg == parsed[in + 4].arg
&& (parsed[in + 3].cmd == INC || parsed[in + 3].cmd == DEC)
&& parsed[in + 3].arg == 1)
{
// This mustn't make the move when the cell is zero already
parsed[out] = parsed[in];
parsed[out + 1] = INSTRUCTION (EAT, 0);
parsed[out + 2] = parsed[in + 2];
parsed[out + 3] = INSTRUCTION
(parsed[in + 3].cmd == INC ? INCACC : DECACC, 0);
parsed[out + 4] = parsed[in + 4];
// This disables the looping further in the code;
// this doesn't have much of an effect in practice
parsed[out + 5] = INSTRUCTION (END, 0);
in += 5;
out += 5;
}
// The simpler case that cannot crash and thus can avoid the loop
else if (in + 5 < parsed_len
&& parsed[in].cmd == BEGIN && parsed[in + 5].cmd == END
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == RIGHT && parsed[in + 4].cmd == LEFT
&& parsed[in + 2].arg == parsed[in + 4].arg
&& (parsed[in + 3].cmd == INC || parsed[in + 3].cmd == DEC)
&& parsed[in + 3].arg == 1)
{
parsed[out] = INSTRUCTION (EAT, 0);
parsed[out + 1] = parsed[in + 2];
parsed[out + 2] = INSTRUCTION
(parsed[in + 3].cmd == INC ? INCACC : DECACC, 0);
parsed[out + 3] = parsed[in + 4];
in += 5;
out += 3;
}
else if (in + 2 < parsed_len
&& parsed[in ].cmd == BEGIN
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == END)
{
parsed[out] = INSTRUCTION (SET, 0);
in += 2;
}
else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC)
parsed[--out].arg += parsed[in].arg;
else if (out != in)
parsed[out] = parsed[in];
}
parsed_len = out;
for (in = 0, out = 0; in < parsed_len; in++, out++)
{
ssize_t dir = 0;
if (parsed[in].cmd == RIGHT)
dir = parsed[in].arg;
else if (parsed[in].cmd == LEFT)
dir = -(ssize_t) parsed[in].arg;
else
{
parsed[out] = parsed[in];
continue;
}
for (; in + 1 < parsed_len; in++)
{
if (parsed[in + 1].cmd == RIGHT)
dir += parsed[in + 1].arg;
else if (parsed[in + 1].cmd == LEFT)
dir -= (ssize_t) parsed[in + 1].arg;
else
break;
}
if (!dir)
out--;
else if (dir > 0)
parsed[out] = INSTRUCTION (RIGHT, dir);
else
parsed[out] = INSTRUCTION (LEFT, -dir);
}
parsed_len = out;
debug_dump ("bf-optimized.txt", parsed, parsed_len);
// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t nesting = 0;
size_t *stack = xcalloc (sizeof *stack, parsed_len);
for (size_t i = 0; i < parsed_len; i++)
{
switch (parsed[i].cmd)
{
case BEGIN:
stack[nesting++] = i;
break;
case END:
assert (nesting > 0);
--nesting;
parsed[stack[nesting]].arg = i + 1;
// Looping can be disabled by optimizations
if (parsed[i].arg)
parsed[i].arg = stack[nesting] + 1;
default:
break;
}
}
free (stack);
assert (nesting == 0);
debug_dump ("bf-final.txt", parsed, parsed_len);
// - - JIT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Functions preserve the registers rbx, rsp, rbp, r12, r13, r14, and r15;
// while rax, rdi, rsi, rdx, rcx, r8, r9, r10, r11 are scratch registers.
str_init (&program);
size_t *offsets = xcalloc (sizeof *offsets, parsed_len + 1);
uint8_t *arith = xcalloc (sizeof *arith, parsed_len);
#define CODE(x) { char t[] = x; str_append_data (&program, t, sizeof t - 1); }
#define WORD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 8); }
#define DWRD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 4); }
CODE ("\x49\xBD") WORD (&dataptr) // mov r13, qword "&dataptr"
CODE ("\x49\xBF") WORD (&data.str) // mov r15, qword "&data.str"
CODE ("\x4D\x8B\x37") // mov r14, qword [r15]
CODE ("\x30\xDB") // xor bl, bl
for (size_t i = 0; i < parsed_len; i++)
{
offsets[i] = program.len;
size_t arg = parsed[i].arg;
assert (arg <= UINT32_MAX);
switch (parsed[i].cmd)
{
case RIGHT:
CODE ("\x41\x88\x1E") // mov [r14], bl
CODE ("\xBF") DWRD (arg) // mov edi, "arg"
CODE ("\x48\xB8") WORD (right) // mov rax, "right"
CODE ("\xFF\xD0") // call rax
// The data could get reallocated, so reload the address
CODE ("\x4D\x8B\x37") // mov r14, qword [r15]
CODE ("\x4D\x03\x75\x00") // add r14, [r13]
break;
case LEFT:
CODE ("\x41\x88\x1E") // mov [r14], bl
CODE ("\xBF") DWRD (arg) // mov edi, "arg"
CODE ("\x49\x29\xFE") // sub r14, rdi -- optimistic
CODE ("\x48\xB8") WORD (left) // mov rax, "left"
CODE ("\xFF\xD0") // call rax
break;
case EAT:
CODE ("\x41\x88\xDC") // mov r12b, bl
CODE ("\x30\xDB") // xor bl, bl
arith[i] = 1;
break;
case INCACC:
CODE ("\x44\x00\xE3") // add bl, r12b
arith[i] = 1;
break;
case DECACC:
CODE ("\x44\x28\xE3") // sub bl, r12b
arith[i] = 1;
break;
case INC:
CODE ("\x80\xC3") // add bl, "arg"
str_append_c (&program, arg);
arith[i] = 1;
break;
case DEC:
CODE ("\x80\xEB") // sub bl, "arg"
str_append_c (&program, arg);
arith[i] = 1;
break;
case SET:
CODE ("\xB3") // mov bl, "arg"
str_append_c (&program, arg);
break;
case OUT:
CODE ("\x48\x0F\xB6\xFB") // movzx rdi, bl
CODE ("\x48\xBE") WORD (stdout) // mov rsi, "stdout"
CODE ("\x48\xB8") WORD (fputc) // mov rax, "fputc"
CODE ("\xFF\xD0") // call rax
break;
case IN:
CODE ("\x48\xB8") WORD (cin) // mov rax, "cin"
CODE ("\xFF\xD0") // call rax
CODE ("\x41\x8A\x1E") // mov bl, [r14]
break;
case BEGIN:
// Don't test the register when the flag has been set already;
// this doesn't have much of an effect in practice
if (!i || !arith[i - 1])
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x84\x00\x00\x00\x00") // jz "offsets[i]"
break;
case END:
// We know that the cell is zero, make this an "if", not a "loop";
// this doesn't have much of an effect in practice
if (!arg)
break;
if (!i || !arith[i - 1])
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x85\x00\x00\x00\x00") // jnz "offsets[i]"
break;
}
// No sense in reading it out when we overwrite it immediately;
// this doesn't have much of an effect in practice
if (parsed[i].cmd == LEFT || parsed[i].cmd == RIGHT)
if (i + 1 >= parsed_len
|| parsed[i + 1].cmd != SET)
CODE ("\x41\x8A\x1E") // mov bl, [r14]
}
// When there is a loop at the end we need to be able to jump past it
offsets[parsed_len] = program.len;
str_append_c (&program, '\xC3'); // ret
// Now that we know where each instruction is, fill in relative jumps;
// this must accurately reflect code generators for BEGIN and END
for (size_t i = 0; i < parsed_len; i++)
{
if ((parsed[i].cmd != BEGIN && parsed[i].cmd != END)
|| !parsed[i].arg)
continue;
size_t fixup = offsets[i] + 2;
if (!i || !arith[i - 1])
fixup += 2;
*(int32_t *)(program.str + fixup) =
((intptr_t)(offsets[parsed[i].arg]) - (intptr_t)(fixup + 4));
}
free (offsets);
free (arith);
#ifdef DEBUG
FILE *bin = fopen ("bf-jit.bin", "w");
fwrite (program.str, program.len, 1, bin);
fclose (bin);
#endif
// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Some systems may have W^X
void *executable = mmap (NULL, program.len, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!executable)
exit_fatal ("mmap: %s\n", strerror (errno));
memcpy (executable, program.str, program.len);
if (mprotect (executable, program.len, PROT_READ | PROT_EXEC))
exit_fatal ("mprotect: %s\n", strerror (errno));
str_init (&data);
str_append_c (&data, 0);
((void (*) (void)) executable)();
return 0;
}

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// This is an exercise in futility more than anything else
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#if (defined __x86_64__ || defined __amd64__) && defined __unix__
#include <unistd.h>
#include <sys/mman.h>
#else
#error Platform not supported
#endif
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xcalloc (size_t m, size_t n)
{
void *p = calloc (m, n);
if (!p)
exit_fatal ("calloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->len = 0;
self->str = xcalloc (1, (self->alloc = 16));
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Application -------------------------------------------------------------
enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END,
EAT, INCACC, DECACC };
bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
struct instruction { enum command cmd; int offset; size_t arg; };
#define INSTRUCTION(c, o, a) (struct instruction) { (c), (o), (a) }
// - - Callbacks - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
FILE *input; ///< User input
static int
cin (void)
{
int c = fgetc (input);
assert (c != EOF);
return c;
}
// - - Main - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#ifdef DEBUG
static void
debug_dump (const char *filename, struct instruction *in, size_t len)
{
FILE *fp = fopen (filename, "w");
long indent = 0;
for (size_t i = 0; i < len; i++)
{
if (in[i].cmd == END)
indent--;
for (long k = 0; k < indent; k++)
fprintf (fp, " ");
switch (in[i].cmd)
{
case RIGHT: fputs ("RIGHT ", fp); break;
case LEFT: fputs ("LEFT ", fp); break;
case INC: fputs ("INC ", fp); break;
case DEC: fputs ("DEC ", fp); break;
case OUT: fputs ("OUT ", fp); break;
case IN: fputs ("IN ", fp); break;
case BEGIN: fputs ("BEGIN ", fp); break;
case END: fputs ("END ", fp); break;
case SET: fputs ("SET ", fp); break;
case EAT: fputs ("EAT ", fp); break;
case INCACC: fputs ("INCACC", fp); break;
case DECACC: fputs ("DECACC", fp); break;
}
fprintf (fp, " %zu [%d]\n", in[i].arg, in[i].offset);
if (in[i].cmd == BEGIN)
indent++;
}
fclose (fp);
}
#else
#define debug_dump(...)
#endif
int
main (int argc, char *argv[])
{
(void) argc;
(void) argv;
struct str program;
str_init (&program);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
if (!(input = fopen ("/dev/tty", "rb")))
exit_fatal ("can't open terminal for reading\n");
// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct instruction *parsed = xcalloc (sizeof *parsed, program.len);
size_t parsed_len = 0;
for (size_t i = 0; i < program.len; i++)
{
enum command cmd;
switch (program.str[i])
{
case '>': cmd = RIGHT; break;
case '<': cmd = LEFT; break;
case '+': cmd = INC; break;
case '-': cmd = DEC; break;
case '.': cmd = OUT; break;
case ',': cmd = IN; break;
case '[': cmd = BEGIN; break;
case ']': cmd = END; break;
default: continue;
}
// The most basic optimization is to group identical commands together
if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd)
parsed_len++;
parsed[parsed_len - 1].cmd = cmd;
parsed[parsed_len - 1].arg++;
}
// - - Optimization passes - - - - - - - - - - - - - - - - - - - - - - - - - - -
debug_dump ("bf-no-opt.txt", parsed, parsed_len);
size_t in = 0, out = 0;
for (; in < parsed_len; in++, out++)
{
if (in + 2 < parsed_len
&& parsed[in ].cmd == BEGIN
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == END)
{
parsed[out] = INSTRUCTION (SET, 0, 0);
in += 2;
}
else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC)
parsed[--out].arg += parsed[in].arg;
else if (out != in)
parsed[out] = parsed[in];
}
parsed_len = out;
debug_dump ("bf-pre-offsets.txt", parsed, parsed_len);
// Add offsets to INC/DEC/SET stuck between LEFT/RIGHT
// and compress the LEFT/RIGHT sequences
for (in = 0, out = 0; in < parsed_len; in++, out++)
{
ssize_t dir = 0;
if (parsed[in].cmd == RIGHT)
dir = parsed[in].arg;
else if (parsed[in].cmd == LEFT)
dir = -(ssize_t) parsed[in].arg;
else
{
parsed[out] = parsed[in];
continue;
}
while (in + 2 < parsed_len)
{
// An immediate offset has its limits
if (dir < INT8_MIN || dir > INT8_MAX)
break;
ssize_t diff;
if (parsed[in + 2].cmd == RIGHT)
diff = parsed[in + 2].arg;
else if (parsed[in + 2].cmd == LEFT)
diff = -(ssize_t) parsed[in + 2].arg;
else
break;
int cmd = parsed[in + 1].cmd;
if (cmd != INC && cmd != DEC && cmd != SET)
break;
parsed[out] = parsed[in + 1];
parsed[out].offset = dir;
dir += diff;
out += 1;
in += 2;
}
for (; in + 1 < parsed_len; in++)
{
if (parsed[in + 1].cmd == RIGHT)
dir += parsed[in + 1].arg;
else if (parsed[in + 1].cmd == LEFT)
dir -= (ssize_t) parsed[in + 1].arg;
else
break;
}
if (!dir)
out--;
else if (dir > 0)
parsed[out] = INSTRUCTION (RIGHT, 0, dir);
else
parsed[out] = INSTRUCTION (LEFT, 0, -dir);
}
parsed_len = out;
debug_dump ("bf-pre-incdec-unloop.txt", parsed, parsed_len);
// Try to eliminate loops that eat a cell and add/subtract its value
// to/from some other cell
for (in = 0, out = 0; in < parsed_len; in++, out++)
{
parsed[out] = parsed[in];
if (parsed[in].cmd != BEGIN)
continue;
bool ok = false;
size_t count = 0;
for (size_t k = in + 1; k < parsed_len; k++)
{
if (parsed[k].cmd == END)
{
ok = true;
break;
}
if (parsed[k].cmd != INC
&& parsed[k].cmd != DEC)
break;
count++;
}
if (!ok)
continue;
// Stable sort operations by their offsets, put [0] first
bool sorted;
do
{
sorted = true;
for (size_t k = 1; k < count; k++)
{
if (parsed[in + k].offset == 0)
continue;
if (parsed[in + k + 1].offset != 0
&& parsed[in + k].offset <= parsed[in + k + 1].offset)
continue;
struct instruction tmp = parsed[in + k + 1];
parsed[in + k + 1] = parsed[in + k];
parsed[in + k] = tmp;
sorted = false;
}
}
while (!sorted);
// Abort the optimization on duplicate offsets (complication with [0])
for (size_t k = 1; k < count; k++)
if (parsed[in + k].offset == parsed[in + k + 1].offset)
ok = false;
// XXX: can't make the code longer either
for (size_t k = 1; k <= count; k++)
if (parsed[in + k].arg != 1)
ok = false;
if (!ok
|| parsed[in + 1].cmd != DEC
|| parsed[in + 1].offset != 0)
continue;
int min_safe_left_offset = 0;
if (in > 1 && parsed[in - 1].cmd == RIGHT)
min_safe_left_offset = -parsed[in - 1].arg;
bool cond_needed_for_safety = false;
for (size_t k = 0; k < count; k++)
if (parsed[in + k + 1].offset < min_safe_left_offset)
{
cond_needed_for_safety = true;
break;
}
in++;
if (cond_needed_for_safety)
out++;
parsed[out] = INSTRUCTION (EAT, 0, 0);
for (size_t k = 1; k < count; k++)
parsed[out + k] = INSTRUCTION (parsed[in + k].cmd == INC
? INCACC : DECACC, parsed[in + k].offset, 0);
in += count;
out += count;
if (cond_needed_for_safety)
parsed[out] = INSTRUCTION (END, 0, 0);
else
out--;
}
parsed_len = out;
debug_dump ("bf-optimized.txt", parsed, parsed_len);
// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t nesting = 0;
size_t *stack = xcalloc (sizeof *stack, parsed_len);
for (size_t i = 0; i < parsed_len; i++)
{
switch (parsed[i].cmd)
{
case BEGIN:
stack[nesting++] = i;
break;
case END:
assert (nesting > 0);
--nesting;
parsed[stack[nesting]].arg = i + 1;
// Looping can be disabled by optimizations
if (parsed[i].arg)
parsed[i].arg = stack[nesting] + 1;
default:
break;
}
}
free (stack);
assert (nesting == 0);
debug_dump ("bf-final.txt", parsed, parsed_len);
// - - JIT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Functions preserve the registers rbx, rsp, rbp, r12, r13, r14, and r15;
// while rax, rdi, rsi, rdx, rcx, r8, r9, r10, r11 are scratch registers.
str_init (&program);
size_t *offsets = xcalloc (sizeof *offsets, parsed_len + 1);
uint8_t *arith = xcalloc (sizeof *arith, parsed_len);
#define CODE(x) { char t[] = x; str_append_data (&program, t, sizeof t - 1); }
#define WORD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 8); }
#define DWRD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 4); }
CODE ("\x48\x89\xF8") // mov rax, rdi
CODE ("\x30\xDB") // xor bl, bl
for (size_t i = 0; i < parsed_len; i++)
{
offsets[i] = program.len;
size_t arg = parsed[i].arg;
assert (arg <= UINT32_MAX);
int offset = parsed[i].offset;
assert (offset <= INT8_MAX && offset >= INT8_MIN);
// Don't save what we've just loaded
if (parsed[i].cmd == LEFT || parsed[i].cmd == RIGHT)
if (i < 2 || i + 1 >= parsed_len
|| (parsed[i - 2].cmd != LEFT && parsed[i - 2].cmd != RIGHT)
|| parsed[i - 1].cmd != BEGIN
|| parsed[i + 1].cmd != END)
CODE ("\x88\x18") // mov [rax], bl
switch (parsed[i].cmd)
{
case RIGHT:
// add rax, "arg" -- optimistic, no boundary checking
if (arg > INT8_MAX)
{ CODE ("\x48\x05") DWRD (arg) }
else
{ CODE ("\x48\x83\xC0") str_append_c (&program, arg); }
break;
case LEFT:
// sub rax, "arg" -- optimistic, no boundary checking
if (arg > INT8_MAX)
{ CODE ("\x48\x2D") DWRD (arg) }
else
{ CODE ("\x48\x83\xE8") str_append_c (&program, arg); }
break;
case EAT:
CODE ("\x41\x88\xDC") // mov r12b, bl
CODE ("\x30\xDB") // xor bl, bl
arith[i] = 1;
break;
case INCACC:
if (offset)
{
CODE ("\x44\x00\x60") // add [rax+"offset"], r12b
str_append_c (&program, offset);
}
else
{
CODE ("\x44\x00\xE3") // add bl, r12b
arith[i] = 1;
}
break;
case DECACC:
if (offset)
{
CODE ("\x44\x28\x60") // sub [rax+"offset"], r12b
str_append_c (&program, offset);
}
else
{
CODE ("\x44\x28\xE3") // sub bl, r12b
arith[i] = 1;
}
break;
case INC:
if (offset)
{
CODE ("\x80\x40") // add byte [rax+"offset"], "arg"
str_append_c (&program, offset);
}
else
{
arith[i] = 1;
CODE ("\x80\xC3") // add bl, "arg"
}
str_append_c (&program, arg);
break;
case DEC:
if (offset)
{
CODE ("\x80\x68") // sub byte [rax+"offset"], "arg"
str_append_c (&program, offset);
}
else
{
arith[i] = 1;
CODE ("\x80\xEB") // sub bl, "arg"
}
str_append_c (&program, arg);
break;
case SET:
if (offset)
{
CODE ("\xC6\x40") // mov byte [rax+"offset"], "arg"
str_append_c (&program, offset);
}
else
CODE ("\xB3") // mov bl, "arg"
str_append_c (&program, arg);
break;
case OUT:
CODE ("\x50\x53") // push rax, push rbx
CODE ("\x48\x0F\xB6\xFB") // movzx rdi, bl
CODE ("\x48\xBE") WORD (stdout) // mov rsi, "stdout"
CODE ("\x48\xB8") WORD (fputc) // mov rax, "fputc"
CODE ("\xFF\xD0") // call rax
CODE ("\x5B\x58") // pop rbx, pop rax
break;
case IN:
CODE ("\x50") // push rax
CODE ("\x48\xB8") WORD (cin) // mov rax, "cin"
CODE ("\xFF\xD0") // call rax
CODE ("\x88\xC3") // mov bl, al
CODE ("\x58") // pop rax
break;
case BEGIN:
// Don't test the register when the flag has been set already;
// this doesn't have much of an effect in practice
if (!i || !arith[i - 1])
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x84\x00\x00\x00\x00") // jz "offsets[i]"
break;
case END:
// We know that the cell is zero, make this an "if", not a "loop";
// this doesn't have much of an effect in practice
if (!arg)
break;
if (!i || !arith[i - 1])
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x85\x00\x00\x00\x00") // jnz "offsets[i]"
break;
}
// No sense in reading it out when we overwrite it immediately;
// this doesn't have much of an effect in practice
if (parsed[i].cmd == LEFT || parsed[i].cmd == RIGHT)
if (i + 1 >= parsed_len
|| parsed[i + 1].cmd != SET
|| parsed[i + 1].offset != 0)
CODE ("\x8A\x18") // mov bl, [rax]
}
// When there is a loop at the end we need to be able to jump past it
offsets[parsed_len] = program.len;
str_append_c (&program, '\xC3'); // ret
// Now that we know where each instruction is, fill in relative jumps;
// this must accurately reflect code generators for BEGIN and END
for (size_t i = 0; i < parsed_len; i++)
{
if ((parsed[i].cmd != BEGIN && parsed[i].cmd != END)
|| !parsed[i].arg)
continue;
size_t fixup = offsets[i] + 2;
if (!i || !arith[i - 1])
fixup += 2;
*(int32_t *)(program.str + fixup) =
((intptr_t)(offsets[parsed[i].arg]) - (intptr_t)(fixup + 4));
}
free (offsets);
free (arith);
#ifdef DEBUG
FILE *bin = fopen ("bf-jit.bin", "w");
fwrite (program.str, program.len, 1, bin);
fclose (bin);
#endif
// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Some systems may have W^X
void *executable = mmap (NULL, program.len, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!executable)
exit_fatal ("mmap: %s\n", strerror (errno));
memcpy (executable, program.str, program.len);
if (mprotect (executable, program.len, PROT_READ | PROT_EXEC))
exit_fatal ("mprotect: %s\n", strerror (errno));
// We create crash zones on both ends of the tape for some minimum safety
long pagesz = sysconf (_SC_PAGESIZE);
assert (pagesz > 0);
const size_t tape_len = (1 << 20) + 2 * pagesz;
char *tape = mmap (NULL, tape_len, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!tape)
exit_fatal ("mmap: %s\n", strerror (errno));
memset (tape, 0, tape_len);
if (mprotect (tape, pagesz, PROT_NONE)
|| mprotect (tape + tape_len - pagesz, pagesz, PROT_NONE))
exit_fatal ("mprotect: %s\n", strerror (errno));
((void (*) (char *)) executable)(tape + pagesz);
return 0;
}

495
interpreters/bf-jit-unsafe.c Normal file
View File

@@ -0,0 +1,495 @@
// This is an exercise in futility more than anything else
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#if (defined __x86_64__ || defined __amd64__) && defined __unix__
#include <unistd.h>
#include <sys/mman.h>
#else
#error Platform not supported
#endif
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xcalloc (size_t m, size_t n)
{
void *p = calloc (m, n);
if (!p)
exit_fatal ("calloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->len = 0;
self->str = xcalloc (1, (self->alloc = 16));
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Application -------------------------------------------------------------
enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END,
EAT, INCACC, DECACC };
bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
struct instruction { enum command cmd; size_t arg; };
#define INSTRUCTION(c, a) (struct instruction) { (c), (a) }
// - - Callbacks - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
FILE *input; ///< User input
static int
cin (void)
{
int c = fgetc (input);
assert (c != EOF);
return c;
}
// - - Main - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#ifdef DEBUG
static void
debug_dump (const char *filename, struct instruction *in, size_t len)
{
FILE *fp = fopen (filename, "w");
long indent = 0;
for (size_t i = 0; i < len; i++)
{
if (in[i].cmd == END)
indent--;
for (long k = 0; k < indent; k++)
fprintf (fp, " ");
switch (in[i].cmd)
{
case RIGHT: fprintf (fp, "RIGHT %zu\n", in[i].arg); break;
case LEFT: fprintf (fp, "LEFT %zu\n", in[i].arg); break;
case INC: fprintf (fp, "INC %zu\n", in[i].arg); break;
case DEC: fprintf (fp, "DEC %zu\n", in[i].arg); break;
case OUT: fprintf (fp, "OUT %zu\n", in[i].arg); break;
case IN: fprintf (fp, "IN %zu\n", in[i].arg); break;
case BEGIN: fprintf (fp, "BEGIN %zu\n", in[i].arg); break;
case END: fprintf (fp, "END %zu\n", in[i].arg); break;
case SET: fprintf (fp, "SET %zu\n", in[i].arg); break;
case EAT: fprintf (fp, "EAT %zu\n", in[i].arg); break;
case INCACC: fprintf (fp, "INCACC %zu\n", in[i].arg); break;
case DECACC: fprintf (fp, "DECACC %zu\n", in[i].arg); break;
}
if (in[i].cmd == BEGIN)
indent++;
}
fclose (fp);
}
#else
#define debug_dump(...)
#endif
int
main (int argc, char *argv[])
{
(void) argc;
(void) argv;
struct str program;
str_init (&program);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
if (!(input = fopen ("/dev/tty", "rb")))
exit_fatal ("can't open terminal for reading\n");
// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct instruction *parsed = xcalloc (sizeof *parsed, program.len);
size_t parsed_len = 0;
for (size_t i = 0; i < program.len; i++)
{
enum command cmd;
switch (program.str[i])
{
case '>': cmd = RIGHT; break;
case '<': cmd = LEFT; break;
case '+': cmd = INC; break;
case '-': cmd = DEC; break;
case '.': cmd = OUT; break;
case ',': cmd = IN; break;
case '[': cmd = BEGIN; break;
case ']': cmd = END; break;
default: continue;
}
// The most basic optimization is to group identical commands together
if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd)
parsed_len++;
parsed[parsed_len - 1].cmd = cmd;
parsed[parsed_len - 1].arg++;
}
// - - Optimization passes - - - - - - - - - - - - - - - - - - - - - - - - - - -
debug_dump ("bf-no-opt.txt", parsed, parsed_len);
size_t in = 0, out = 0;
for (; in < parsed_len; in++, out++)
{
// This shows up in mandelbrot.bf a lot but actually helps hanoi.bf
if (in + 5 < parsed_len
&& parsed[in].cmd == BEGIN && parsed[in + 5].cmd == END
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == LEFT && parsed[in + 4].cmd == RIGHT
&& parsed[in + 2].arg == parsed[in + 4].arg
&& (parsed[in + 3].cmd == INC || parsed[in + 3].cmd == DEC)
&& parsed[in + 3].arg == 1)
{
// This mustn't make the move when the cell is zero already
parsed[out] = parsed[in];
parsed[out + 1] = INSTRUCTION (EAT, 0);
parsed[out + 2] = parsed[in + 2];
parsed[out + 3] = INSTRUCTION
(parsed[in + 3].cmd == INC ? INCACC : DECACC, 0);
parsed[out + 4] = parsed[in + 4];
// This disables the looping further in the code;
// this doesn't have much of an effect in practice
parsed[out + 5] = INSTRUCTION (END, 0);
in += 5;
out += 5;
}
// The simpler case that cannot crash and thus can avoid the loop
else if (in + 5 < parsed_len
&& parsed[in].cmd == BEGIN && parsed[in + 5].cmd == END
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == RIGHT && parsed[in + 4].cmd == LEFT
&& parsed[in + 2].arg == parsed[in + 4].arg
&& (parsed[in + 3].cmd == INC || parsed[in + 3].cmd == DEC)
&& parsed[in + 3].arg == 1)
{
parsed[out] = INSTRUCTION (EAT, 0);
parsed[out + 1] = parsed[in + 2];
parsed[out + 2] = INSTRUCTION
(parsed[in + 3].cmd == INC ? INCACC : DECACC, 0);
parsed[out + 3] = parsed[in + 4];
in += 5;
out += 3;
}
else if (in + 2 < parsed_len
&& parsed[in ].cmd == BEGIN
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == END)
{
parsed[out] = INSTRUCTION (SET, 0);
in += 2;
}
else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC)
parsed[--out].arg += parsed[in].arg;
else if (out != in)
parsed[out] = parsed[in];
}
parsed_len = out;
for (in = 0, out = 0; in < parsed_len; in++, out++)
{
ssize_t dir = 0;
if (parsed[in].cmd == RIGHT)
dir = parsed[in].arg;
else if (parsed[in].cmd == LEFT)
dir = -(ssize_t) parsed[in].arg;
else
{
parsed[out] = parsed[in];
continue;
}
for (; in + 1 < parsed_len; in++)
{
if (parsed[in + 1].cmd == RIGHT)
dir += parsed[in + 1].arg;
else if (parsed[in + 1].cmd == LEFT)
dir -= (ssize_t) parsed[in + 1].arg;
else
break;
}
if (!dir)
out--;
else if (dir > 0)
parsed[out] = INSTRUCTION (RIGHT, dir);
else
parsed[out] = INSTRUCTION (LEFT, -dir);
}
parsed_len = out;
debug_dump ("bf-optimized.txt", parsed, parsed_len);
// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t nesting = 0;
size_t *stack = xcalloc (sizeof *stack, parsed_len);
for (size_t i = 0; i < parsed_len; i++)
{
switch (parsed[i].cmd)
{
case BEGIN:
stack[nesting++] = i;
break;
case END:
assert (nesting > 0);
--nesting;
parsed[stack[nesting]].arg = i + 1;
// Looping can be disabled by optimizations
if (parsed[i].arg)
parsed[i].arg = stack[nesting] + 1;
default:
break;
}
}
free (stack);
assert (nesting == 0);
debug_dump ("bf-final.txt", parsed, parsed_len);
// - - JIT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Functions preserve the registers rbx, rsp, rbp, r12, r13, r14, and r15;
// while rax, rdi, rsi, rdx, rcx, r8, r9, r10, r11 are scratch registers.
str_init (&program);
size_t *offsets = xcalloc (sizeof *offsets, parsed_len + 1);
uint8_t *arith = xcalloc (sizeof *arith, parsed_len);
#define CODE(x) { char t[] = x; str_append_data (&program, t, sizeof t - 1); }
#define WORD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 8); }
#define DWRD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 4); }
CODE ("\x48\x89\xF8") // mov rax, rdi
CODE ("\x30\xDB") // xor bl, bl
for (size_t i = 0; i < parsed_len; i++)
{
offsets[i] = program.len;
size_t arg = parsed[i].arg;
assert (arg <= UINT32_MAX);
// Don't save what we've just loaded
if (parsed[i].cmd == LEFT || parsed[i].cmd == RIGHT)
if (i < 2 || i + 1 >= parsed_len
|| (parsed[i - 2].cmd != LEFT && parsed[i - 2].cmd != RIGHT)
|| parsed[i - 1].cmd != BEGIN
|| parsed[i + 1].cmd != END)
CODE ("\x88\x18") // mov [rax], bl
switch (parsed[i].cmd)
{
case RIGHT:
// add rax, "arg" -- optimistic, no boundary checking
if (arg > INT8_MAX)
{ CODE ("\x48\x05") DWRD (arg) }
else
{ CODE ("\x48\x83\xC0") str_append_c (&program, arg); }
break;
case LEFT:
// sub rax, "arg" -- optimistic, no boundary checking
if (arg > INT8_MAX)
{ CODE ("\x48\x2D") DWRD (arg) }
else
{ CODE ("\x48\x83\xE8") str_append_c (&program, arg); }
break;
case EAT:
CODE ("\x41\x88\xDC") // mov r12b, bl
CODE ("\x30\xDB") // xor bl, bl
arith[i] = 1;
break;
case INCACC:
CODE ("\x44\x00\xE3") // add bl, r12b
arith[i] = 1;
break;
case DECACC:
CODE ("\x44\x28\xE3") // sub bl, r12b
arith[i] = 1;
break;
case INC:
CODE ("\x80\xC3") // add bl, "arg"
str_append_c (&program, arg);
arith[i] = 1;
break;
case DEC:
CODE ("\x80\xEB") // sub bl, "arg"
str_append_c (&program, arg);
arith[i] = 1;
break;
case SET:
CODE ("\xB3") // mov bl, "arg"
str_append_c (&program, arg);
break;
case OUT:
CODE ("\x50\x53") // push rax, push rbx
CODE ("\x48\x0F\xB6\xFB") // movzx rdi, bl
CODE ("\x48\xBE") WORD (stdout) // mov rsi, "stdout"
CODE ("\x48\xB8") WORD (fputc) // mov rax, "fputc"
CODE ("\xFF\xD0") // call rax
CODE ("\x5B\x58") // pop rbx, pop rax
break;
case IN:
CODE ("\x50") // push rax
CODE ("\x48\xB8") WORD (cin) // mov rax, "cin"
CODE ("\xFF\xD0") // call rax
CODE ("\x88\xC3") // mov bl, al
CODE ("\x58") // pop rax
break;
case BEGIN:
// Don't test the register when the flag has been set already;
// this doesn't have much of an effect in practice
if (!i || !arith[i - 1])
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x84\x00\x00\x00\x00") // jz "offsets[i]"
break;
case END:
// We know that the cell is zero, make this an "if", not a "loop";
// this doesn't have much of an effect in practice
if (!arg)
break;
if (!i || !arith[i - 1])
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x85\x00\x00\x00\x00") // jnz "offsets[i]"
break;
}
// No sense in reading it out when we overwrite it immediately;
// this doesn't have much of an effect in practice
if (parsed[i].cmd == LEFT || parsed[i].cmd == RIGHT)
if (i + 1 >= parsed_len
|| parsed[i + 1].cmd != SET)
CODE ("\x8A\x18") // mov bl, [rax]
}
// When there is a loop at the end we need to be able to jump past it
offsets[parsed_len] = program.len;
str_append_c (&program, '\xC3'); // ret
// Now that we know where each instruction is, fill in relative jumps;
// this must accurately reflect code generators for BEGIN and END
for (size_t i = 0; i < parsed_len; i++)
{
if ((parsed[i].cmd != BEGIN && parsed[i].cmd != END)
|| !parsed[i].arg)
continue;
size_t fixup = offsets[i] + 2;
if (!i || !arith[i - 1])
fixup += 2;
*(int32_t *)(program.str + fixup) =
((intptr_t)(offsets[parsed[i].arg]) - (intptr_t)(fixup + 4));
}
free (offsets);
free (arith);
#ifdef DEBUG
FILE *bin = fopen ("bf-jit.bin", "w");
fwrite (program.str, program.len, 1, bin);
fclose (bin);
#endif
// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Some systems may have W^X
void *executable = mmap (NULL, program.len, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!executable)
exit_fatal ("mmap: %s\n", strerror (errno));
memcpy (executable, program.str, program.len);
if (mprotect (executable, program.len, PROT_READ | PROT_EXEC))
exit_fatal ("mprotect: %s\n", strerror (errno));
// We create crash zones on both ends of the tape for some minimum safety
long pagesz = sysconf (_SC_PAGESIZE);
assert (pagesz > 0);
const size_t tape_len = (1 << 20) + 2 * pagesz;
char *tape = mmap (NULL, tape_len, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!tape)
exit_fatal ("mmap: %s\n", strerror (errno));
memset (tape, 0, tape_len);
if (mprotect (tape, pagesz, PROT_NONE)
|| mprotect (tape + tape_len - pagesz, pagesz, PROT_NONE))
exit_fatal ("mprotect: %s\n", strerror (errno));
((void (*) (char *)) executable)(tape + pagesz);
return 0;
}

327
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// This is an exercise in futility more than anything else
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#if (defined __x86_64__ || defined __amd64__) && defined __unix__
#include <sys/mman.h>
#else
#error Platform not supported
#endif
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xcalloc (size_t m, size_t n)
{
void *p = calloc (m, n);
if (!p)
exit_fatal ("calloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->len = 0;
self->str = xcalloc (1, (self->alloc = 16));
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Application -------------------------------------------------------------
struct str data; ///< Data tape
volatile size_t dataptr; ///< Current location on the tape
FILE *input; ///< User input
enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END };
bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0 };
struct instruction { enum command cmd; size_t arg; };
// - - Callbacks - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Some things I just really don't want to write in assembly even though it
// is effectively a big performance hit, eliminating the advantage of JIT
static void
right (size_t arg)
{
assert (SIZE_MAX - dataptr > arg);
dataptr += arg;
while (dataptr >= data.len)
str_append_c (&data, 0);
}
static void
left (size_t arg)
{
assert (dataptr >= arg);
dataptr -= arg;
}
static int
cin (void)
{
int c = fgetc (input);
assert (c != EOF);
return c;
}
// - - Main - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
int
main (int argc, char *argv[])
{
(void) argc;
(void) argv;
struct str program;
str_init (&program);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
if (!(input = fopen ("/dev/tty", "rb")))
exit_fatal ("can't open terminal for reading\n");
// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct instruction *parsed = xcalloc (sizeof *parsed, program.len);
size_t parsed_len = 0;
for (size_t i = 0; i < program.len; i++)
{
enum command cmd;
switch (program.str[i])
{
case '>': cmd = RIGHT; break;
case '<': cmd = LEFT; break;
case '+': cmd = INC; break;
case '-': cmd = DEC; break;
case '.': cmd = OUT; break;
case ',': cmd = IN; break;
case '[': cmd = BEGIN; break;
case ']': cmd = END; break;
default: continue;
}
if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd)
parsed_len++;
parsed[parsed_len - 1].cmd = cmd;
parsed[parsed_len - 1].arg++;
}
// - - Simple optimization pass - - - - - - - - - - - - - - - - - - - - - - - -
size_t in = 0, out = 0;
for (; in < parsed_len; in++, out++)
{
if (in + 2 < parsed_len
&& parsed[in ].cmd == BEGIN
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == END)
{
parsed[out].cmd = SET;
parsed[out].arg = 0;
in += 2;
}
else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC)
parsed[--out].arg += parsed[in].arg;
else if (out != in)
parsed[out] = parsed[in];
}
parsed_len = out;
// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t nesting = 0;
size_t *stack = xcalloc (sizeof *stack, parsed_len);
for (size_t i = 0; i < parsed_len; i++)
{
switch (parsed[i].cmd)
{
case BEGIN:
stack[nesting++] = i;
break;
case END:
assert (nesting > 0);
--nesting;
parsed[stack[nesting]].arg = i + 1;
parsed[i].arg = stack[nesting] + 1;
default:
break;
}
}
free (stack);
assert (nesting == 0);
// - - JIT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Functions preserve the registers rbx, rsp, rbp, r12, r13, r14, and r15;
// while rax, rdi, rsi, rdx, rcx, r8, r9, r10, r11 are scratch registers.
str_init (&program);
size_t *offsets = xcalloc (sizeof *offsets, parsed_len + 1);
#define CODE(x) { char t[] = x; str_append_data (&program, t, sizeof t - 1); }
#define WORD(x) { size_t t = (size_t)(x); str_append_data (&program, &t, 8); }
CODE ("\x49\xBD") WORD (&dataptr) // mov r13, qword "&dataptr"
CODE ("\x49\xBF") WORD (&data.str) // mov r15, qword "&data.str"
CODE ("\x4D\x8B\x37") // mov r14, qword [r15]
CODE ("\x30\xDB") // xor bl, bl
for (size_t i = 0; i < parsed_len; i++)
{
offsets[i] = program.len;
size_t arg = parsed[i].arg;
switch (parsed[i].cmd)
{
case RIGHT:
CODE ("\x41\x88\x1E") // mov [r14], bl
CODE ("\x48\xBF") WORD (arg) // mov rdi, "arg"
CODE ("\x48\xB8") WORD (right) // mov rax, "right"
CODE ("\xFF\xD0") // call rax
// The data could get reallocated, so reload the address
CODE ("\x4D\x8B\x37") // mov r14, qword [r15]
CODE ("\x4D\x03\x75\x00") // add r14, [r13]
CODE ("\x41\x8A\x1E") // mov bl, [r14]
break;
case LEFT:
CODE ("\x41\x88\x1E") // mov [r14], bl
CODE ("\x48\xBF") WORD (arg) // mov rdi, "arg"
CODE ("\x49\x29\xFE") // sub r14, rdi -- optimistic
CODE ("\x48\xB8") WORD (left) // mov rax, "left"
CODE ("\xFF\xD0") // call rax
CODE ("\x41\x8A\x1E") // mov bl, [r14]
break;
case INC:
CODE ("\x80\xC3") // add bl, "arg"
str_append_c (&program, arg);
break;
case DEC:
CODE ("\x80\xEB") // sub bl, "arg"
str_append_c (&program, arg);
break;
case SET:
CODE ("\xB3") // mov bl, "arg"
str_append_c (&program, arg);
break;
case OUT:
CODE ("\x48\x0F\xB6\xFB") // movzx rdi, bl
CODE ("\x48\xBE") WORD (stdout) // mov rsi, "stdout"
CODE ("\x48\xB8") WORD (fputc) // mov rax, "fputc"
CODE ("\xFF\xD0") // call rax
break;
case IN:
CODE ("\x48\xB8") WORD (cin) // mov rax, "cin"
CODE ("\xFF\xD0") // call rax
CODE ("\x88\xC3") // mov bl, al
break;
case BEGIN:
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x84\x00\x00\x00\x00") // jz "offsets[i]"
break;
case END:
CODE ("\x84\xDB") // test bl, bl
CODE ("\x0F\x85\x00\x00\x00\x00") // jnz "offsets[i]"
break;
}
}
// When there is a loop at the end we need to be able to jump past it
offsets[parsed_len] = program.len;
str_append_c (&program, '\xC3'); // ret
// Now that we know where each instruction is, fill in relative jumps
for (size_t i = 0; i < parsed_len; i++)
{
if (parsed[i].cmd != BEGIN && parsed[i].cmd != END)
continue;
size_t fixup = offsets[i] + 4;
*(int32_t *)(program.str + fixup) =
((intptr_t)(offsets[parsed[i].arg]) - (intptr_t)(fixup + 4));
}
free (offsets);
// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Some systems may have W^X
void *executable = mmap (NULL, program.len, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!executable)
exit_fatal ("mmap: %s\n", strerror (errno));
memcpy (executable, program.str, program.len);
if (mprotect (executable, program.len, PROT_READ | PROT_EXEC))
exit_fatal ("mprotect: %s\n", strerror (errno));
str_init (&data);
str_append_c (&data, 0);
((void (*) (void)) executable)();
return 0;
}

213
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xcalloc (size_t m, size_t n)
{
void *p = calloc (m, n);
if (!p)
exit_fatal ("calloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->len = 0;
self->str = xcalloc (1, (self->alloc = 16));
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->str[self->len += n] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Main --------------------------------------------------------------------
struct str program; ///< Raw program
struct str data; ///< Data tape
enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END };
bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0 };
struct instruction { enum command cmd; size_t arg; };
int
main (int argc, char *argv[])
{
(void) argc; str_init (&program);
(void) argv; str_init (&data);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
FILE *input = fopen ("/dev/tty", "rb");
if (!input)
exit_fatal ("can't open terminal for reading\n");
// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct instruction *parsed = xcalloc (sizeof *parsed, program.len);
size_t parsed_len = 0;
for (size_t i = 0; i < program.len; i++)
{
enum command cmd;
switch (program.str[i])
{
case '>': cmd = RIGHT; break;
case '<': cmd = LEFT; break;
case '+': cmd = INC; break;
case '-': cmd = DEC; break;
case '.': cmd = OUT; break;
case ',': cmd = IN; break;
case '[': cmd = BEGIN; break;
case ']': cmd = END; break;
default: continue;
}
if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd)
parsed_len++;
parsed[parsed_len - 1].cmd = cmd;
parsed[parsed_len - 1].arg++;
}
// - - Simple optimization pass - - - - - - - - - - - - - - - - - - - - - - - -
size_t in = 0, out = 0;
for (; in < parsed_len; in++, out++)
{
if (in + 2 < parsed_len
&& parsed[in ].cmd == BEGIN
&& parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1
&& parsed[in + 2].cmd == END)
{
parsed[out].cmd = SET;
parsed[out].arg = 0;
in += 2;
}
else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC)
parsed[--out].arg += parsed[in].arg;
else if (out != in)
parsed[out] = parsed[in];
}
parsed_len = out;
// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t nesting = 0;
size_t *stack = xcalloc (sizeof *stack, parsed_len);
for (size_t i = 0; i < parsed_len; i++)
{
switch (parsed[i].cmd)
{
case BEGIN:
stack[nesting++] = i;
break;
case END:
assert (nesting > 0);
--nesting;
parsed[stack[nesting]].arg = i;
parsed[i].arg = stack[nesting];
default:
break;
}
}
assert (nesting == 0);
// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
size_t dataptr = 0;
str_append_c (&data, 0);
for (size_t i = 0; i < parsed_len; i++)
{
size_t arg = parsed[i].arg;
switch (parsed[i].cmd)
{
case RIGHT:
assert (SIZE_MAX - dataptr > arg);
dataptr += arg;
while (dataptr >= data.len)
str_append_c (&data, 0);
break;
case LEFT:
assert (dataptr >= arg);
dataptr -= arg;
break;
case INC: data.str[dataptr] += arg; break;
case DEC: data.str[dataptr] -= arg; break;
case SET: data.str[dataptr] = arg; break;
case OUT:
fputc (data.str[dataptr], stdout);
break;
case IN:
data.str[dataptr] = c = fgetc (input);
assert (c != EOF);
break;
case BEGIN: if (!data.str[dataptr]) i = arg; break;
case END: if ( data.str[dataptr]) i = arg; break;
}
}
return 0;
}

160
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <assert.h>
#include <errno.h>
#define exit_fatal(...) \
do { \
fprintf (stderr, "fatal: " __VA_ARGS__); \
exit (EXIT_FAILURE); \
} while (0)
// --- Safe memory management --------------------------------------------------
static void *
xmalloc (size_t n)
{
void *p = malloc (n);
if (!p)
exit_fatal ("malloc: %s\n", strerror (errno));
return p;
}
static void *
xrealloc (void *o, size_t n)
{
void *p = realloc (o, n);
if (!p && n)
exit_fatal ("realloc: %s\n", strerror (errno));
return p;
}
// --- Dynamically allocated strings -------------------------------------------
struct str
{
char *str; ///< String data, null terminated
size_t alloc; ///< How many bytes are allocated
size_t len; ///< How long the string actually is
};
static void
str_init (struct str *self)
{
self->alloc = 16;
self->len = 0;
self->str = strcpy (xmalloc (self->alloc), "");
}
static void
str_ensure_space (struct str *self, size_t n)
{
// We allocate at least one more byte for the terminating null character
size_t new_alloc = self->alloc;
while (new_alloc <= self->len + n)
new_alloc <<= 1;
if (new_alloc != self->alloc)
self->str = xrealloc (self->str, (self->alloc = new_alloc));
}
static void
str_append_data (struct str *self, const void *data, size_t n)
{
str_ensure_space (self, n);
memcpy (self->str + self->len, data, n);
self->len += n;
self->str[self->len] = '\0';
}
static void
str_append_c (struct str *self, char c)
{
str_append_data (self, &c, 1);
}
// --- Main --------------------------------------------------------------------
int
main (int argc, char *argv[])
{
struct str program; str_init (&program);
struct str data; str_init (&data);
int c;
while ((c = fgetc (stdin)) != EOF)
str_append_c (&program, c);
if (ferror (stdin))
exit_fatal ("can't read program\n");
FILE *input = fopen ("/dev/tty", "rb");
if (!input)
exit_fatal ("can't open terminal for reading\n");
size_t dataptr = 0;
str_append_c (&data, 0);
for (size_t i = 0; i < program.len; i++)
{
switch (program.str[i])
{
long pairs;
case '>':
assert (dataptr != SIZE_MAX);
dataptr++;
if (dataptr == data.len)
str_append_c (&data, 0);
break;
case '<':
assert (dataptr != 0);
dataptr--;
break;
case '+': data.str[dataptr]++; break;
case '-': data.str[dataptr]--; break;
case '.':
fputc (data.str[dataptr], stdout);
break;
case ',':
data.str[dataptr] = c = fgetc (input);
assert (c != EOF);
break;
case '[':
if (data.str[dataptr]) break;
for (pairs = 0; i < program.len; i++)
{
switch (program.str[i])
{
case '[': pairs++; break;
case ']': pairs--; break;
}
if (!pairs)
break;
}
assert (!pairs);
break;
case ']':
if (!data.str[dataptr]) break;
for (pairs = 0; i != SIZE_MAX; i--)
{
switch (program.str[i])
{
case '[': pairs--; break;
case ']': pairs++; break;
}
if (!pairs)
break;
}
assert (!pairs);
break;
default:
break;
}
}
return 0;
}