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/**
* \file
* Routines for parsing basic blocks from the IL stream
*
* Authors:
* Rodrigo Kumpera (rkumpera@novell.com)
*
* Copyright 2010 Novell, Inc (http://www.novell.com)
* Licensed under the MIT license. See LICENSE file in the project root for full license information.
*/
#include <config.h>
#include <mono/metadata/debug-helpers.h>
#include <mono/metadata/metadata-internals.h>
#include <mono/metadata/mono-endian.h>
#include <mono/metadata/mono-basic-block.h>
#include <mono/metadata/opcodes.h>
#include <mono/utils/mono-error-internals.h>
#include <mono/utils/mono-compiler.h>
#define CHECK_ADD4_OVERFLOW_UN(a, b) ((guint32)(0xFFFFFFFFU) - (guint32)(b) < (guint32)(a))
#define CHECK_ADD8_OVERFLOW_UN(a, b) ((guint64)(0xFFFFFFFFFFFFFFFFUL) - (guint64)(b) < (guint64)(a))
#if SIZEOF_VOID_P == 4
#define CHECK_ADDP_OVERFLOW_UN(a,b) CHECK_ADD4_OVERFLOW_UN(a, b)
#else
#define CHECK_ADDP_OVERFLOW_UN(a,b) CHECK_ADD8_OVERFLOW_UN(a, b)
#endif
#define ADDP_IS_GREATER_OR_OVF(a, b, c) (((a) + (b) > (c)) || CHECK_ADDP_OVERFLOW_UN (a, b))
#define ADD_IS_GREATER_OR_OVF(a, b, c) (((a) + (b) > (c)) || CHECK_ADD4_OVERFLOW_UN (a, b))
#define DEBUG_BB 0
enum {
RED,
BLACK
};
#if DEBUG_BB
static void
dump_bb_list (MonoSimpleBasicBlock *bb, MonoSimpleBasicBlock **root, const char *msg)
{
printf ("------- %s --- root is %x ---\n", msg, (*root)->start);
while (bb) {
GSList *tmp;
printf ("BB start %x end %x left ", bb->start, bb->end);
if (bb->left)
printf ("%x", bb->left->start);
else
printf ("NIL");
printf (" right ");
if (bb->right)
printf ("%x", bb->right->start);
else
printf ("NIL");
printf (" parent ");
if (bb->parent)
printf ("%x", bb->parent->start);
else
printf ("NIL");
printf(" color %s out [", bb->colour == RED ? "red" : "black");
for (tmp = bb->out_bb; tmp; tmp = tmp->next) {
MonoSimpleBasicBlock *to = tmp->data;
printf ("%x ", to->start);
}
printf ("] %s\n", bb->dead ? "dead" : "alive");
bb = bb->next;
}
}
#endif
static void
bb_unlink (MonoSimpleBasicBlock *from, MonoSimpleBasicBlock *to)
{
if (from->out_bb)
from->out_bb = g_slist_remove (from->out_bb, to);
}
static void
bb_link (MonoSimpleBasicBlock *from, MonoSimpleBasicBlock *to)
{
if (g_slist_find (from->out_bb, to))
return;
from->out_bb = g_slist_prepend (from->out_bb, to);
}
static MonoSimpleBasicBlock*
bb_grandparent (MonoSimpleBasicBlock *bb)
{
return bb && bb->parent ? bb->parent->parent : NULL;
}
static MonoSimpleBasicBlock*
bb_uncle (MonoSimpleBasicBlock *bb)
{
MonoSimpleBasicBlock *gp = bb_grandparent (bb);
if (gp == NULL)
return NULL;
if (bb->parent == gp->left)
return gp->right;
return gp->left;
}
static void
change_node (MonoSimpleBasicBlock *from, MonoSimpleBasicBlock *to, MonoSimpleBasicBlock **root)
{
MonoSimpleBasicBlock *parent = from->parent;
if (parent) {
if (parent->left == from)
parent->left = to;
else
parent->right = to;
} else {
*root = to;
}
to->parent = parent;
}
static void
rotate_right (MonoSimpleBasicBlock *parent, MonoSimpleBasicBlock **root)
{
MonoSimpleBasicBlock *bb = parent->left;
if (bb->right) {
parent->left = bb->right;
parent->left->parent = parent;
} else
parent->left = NULL;
bb->right = parent;
change_node (parent, bb, root);
parent->parent = bb;
}
static void
rotate_left (MonoSimpleBasicBlock *bb, MonoSimpleBasicBlock **root)
{
MonoSimpleBasicBlock *other = bb->right;
if (other->left) {
bb->right = other->left;
bb->right->parent = bb;
} else
bb->right = NULL;
other->left = bb;
change_node (bb, other, root);
bb->parent = other;
}
/* School book implementation of a RB tree with insert then fix (which requires a parent pointer)
* TODO implement Sedgewick's version that doesn't require parent pointers
*/
static void
bb_insert (MonoSimpleBasicBlock *first, MonoSimpleBasicBlock *bb, MonoSimpleBasicBlock **root)
{
MonoSimpleBasicBlock *parent, *uncle, *grandparent;
int bb_start = bb->start;
parent = *root;
do {
if (bb_start < parent->start) {
if (parent->left == NULL) {
parent->left = bb;
break;
}
parent = parent->left;
} else {
if (parent->right == NULL) {
parent->right = bb;
break;
}
parent = parent->right;
}
} while (parent);
g_assert (parent);
bb->parent = parent;
bb->colour = RED;
do {
if (bb->parent == NULL) {
bb->colour = BLACK;
break;
}
if (bb->parent->colour == BLACK)
break;
uncle = bb_uncle (bb);
if (uncle && uncle->colour == RED) {
grandparent = bb_grandparent (bb);
bb->parent->colour = BLACK;
uncle->colour = BLACK;
grandparent->colour = RED;
bb = grandparent;
continue;
}
grandparent = bb_grandparent (bb);
if ((bb == bb->parent->right) && (bb->parent == grandparent->left)) {
rotate_left (bb->parent, root);
bb = bb->left;
} else if ((bb == bb->parent->left) && (bb->parent == grandparent->right)) {
rotate_right (bb->parent, root);
bb = bb->right;
}
grandparent = bb_grandparent (bb);
bb->parent->colour = BLACK;
grandparent->colour = RED;
if ((bb == bb->parent->left) && (bb->parent == grandparent->left))
rotate_right (grandparent, root);
else
rotate_left (grandparent, root);
break;
} while (TRUE);
}
static gboolean
bb_idx_is_contained (MonoSimpleBasicBlock *bb, int target)
{
return bb->start <= target && target < bb->end;
}
/*
* Split the basic blocks from @first at @target.
* @hint is a guess of a very close to the target basic block. It is probed before the RB tree as it's often possible
* to provide a near to exact guess (next block splits, switch branch targets, etc)
*
*/
static MonoSimpleBasicBlock*
bb_split (MonoSimpleBasicBlock *first, MonoSimpleBasicBlock *hint, MonoSimpleBasicBlock **root, guint target, gboolean link_blocks, MonoMethod *method, MonoError *error)
{
MonoSimpleBasicBlock *res, *bb = first;
error_init (error);
if (bb_idx_is_contained (hint, target)) {
first = hint;
} else if (hint->next && bb_idx_is_contained (hint->next, target)) {
first = hint->next;
} else {
first = *root;
do {
if (bb_idx_is_contained (first, target))
break;
if (first->start > target)
first = first->left;
else
first = first->right;
} while (first);
}
if (first == NULL) {
mono_error_set_not_verifiable (error, method, "Invalid instruction target %x", target);
return NULL;
}
if (first->start == target)
return first;
res = g_new0 (MonoSimpleBasicBlock, 1);
res->start = target;
res->end = first->end;
res->next = first->next;
res->out_bb = first->out_bb;
res->dead = TRUE;
first->end = res->start;
first->next = res;
first->out_bb = NULL;
if (link_blocks)
bb_link (first, res);
bb_insert (bb, res, root);
return res;
}
static void
bb_liveness (MonoSimpleBasicBlock *bb)
{
GPtrArray* mark_stack = g_ptr_array_new ();
GSList *tmp;
/*All function entry points (prologue, EH handler/filter) are already marked*/
while (bb) {
if (!bb->dead)
g_ptr_array_add (mark_stack, bb);
bb = bb->next;
}
while (mark_stack->len > 0) {
MonoSimpleBasicBlock *block = (MonoSimpleBasicBlock *)g_ptr_array_remove_index_fast (mark_stack, mark_stack->len - 1);
block->dead = FALSE;
for (tmp = block->out_bb; tmp; tmp = tmp->next) {
MonoSimpleBasicBlock *to = (MonoSimpleBasicBlock *)tmp->data;
if (to->dead)
g_ptr_array_add (mark_stack, to);
}
}
g_ptr_array_free (mark_stack, TRUE);
}
/*This doesn't returns endfilter because it's not useful to split at its boundary.
Endfilter must be the last instruction of a filter clause and MS enforces this, so we can't have
dead code after it.
*/
static gboolean
mono_opcode_has_static_branch (int opcode)
{
switch (opcode) {
case MONO_CEE_RET:
case MONO_CEE_THROW:
case MONO_CEE_RETHROW:
case MONO_CEE_ENDFINALLY:
return TRUE;
}
return FALSE;
}
static void
bb_formation_il_pass (const unsigned char *start, const unsigned char *end, MonoSimpleBasicBlock *bb, MonoSimpleBasicBlock **root, MonoMethod *method, MonoError *error)
{
unsigned const char *ip = start;
int value, size;
guint cli_addr, offset;
MonoSimpleBasicBlock *branch, *next, *current;
const MonoOpcode *opcode;
error_init (error);
current = bb;
while (ip < end) {
cli_addr = ip - start;
size = mono_opcode_value_and_size (&ip, end, &value);
if (size < 0) {
mono_error_set_not_verifiable (error, method, "Invalid instruction %x", *ip);
return;
}
while (current && cli_addr >= current->end)
current = current->next;
g_assert (current);
opcode = &mono_opcodes [value];
switch (opcode->argument) {
case MonoInlineNone:
ip++;
if (!mono_opcode_has_static_branch (value) || ip >= end)
break;
if (!(next = bb_split (bb, current, root, ip - start, FALSE, method, error)))
return;
bb_unlink (current, next);
current = next;
break;
case MonoInlineString:
case MonoInlineType:
case MonoInlineField:
case MonoInlineTok:
case MonoInlineSig:
case MonoShortInlineR:
case MonoInlineI:
ip += 5;
break;
case MonoInlineMethod:
ip += 5;
if (value != MONO_CEE_JMP || ip >= end)
break;
if (!(next = bb_split (bb, current, root, ip - start, FALSE, method, error)))
return;
bb_unlink (current, next);
current = next;
break;
case MonoInlineVar:
ip += 3;
break;
case MonoShortInlineVar:
case MonoShortInlineI:
ip += 2;
break;
case MonoInlineR:
case MonoInlineI8:
ip += 9;
break;
case MonoShortInlineBrTarget:
case MonoInlineBrTarget:
if (opcode->argument == MonoShortInlineBrTarget) {
offset = cli_addr + 2 + (signed char)ip [1];
ip += 2;
} else {
offset = cli_addr + 5 + (gint32)read32 (ip + 1);
ip += 5;
}
branch = bb_split (bb, current, root, offset, TRUE, method, error);
if (!branch)
return;
/*If we splitted the current BB*/
if (offset < cli_addr && branch->start > current->start)
current = branch;
if (ip < end) {
next = bb_split (bb, current, root, ip - start, opcode->flow_type != MONO_FLOW_BRANCH, method, error);
if (!next)
return;
} else {
next = NULL;
}
bb_link (current, branch);
if (next && opcode->flow_type == MONO_FLOW_BRANCH && next != branch) {
bb_unlink (current, next);
current = next;
}
break;
case MonoInlineSwitch: {
MonoSimpleBasicBlock *tmp;
guint32 j, n = read32 (ip + 1);
ip += 5;
offset = cli_addr + 5 + 4 * n;
if (!(next = bb_split (bb, current, root, offset, TRUE, method, error)))
return;
bb_link (current, next);
tmp = next;
for (j = 0; j < n; ++j) {
if (ip >= end) {
mono_error_set_not_verifiable (error, method, "Invalid switch instruction %x", cli_addr);
return;
}
if (!(next = bb_split (bb, next, root, offset + (gint32)read32 (ip), TRUE, method, error)))
return;
bb_link (current, next);
ip += 4;
}
current = tmp;
break;
}
default:
mono_error_set_not_verifiable (error, method, "Invalid instruction %x", *ip);
return;
}
}
if (ip != end)
mono_error_set_not_verifiable (error, method, "Invalid last instruction");
}
static void
bb_formation_eh_pass (MonoMethodHeader *header, MonoSimpleBasicBlock *bb, MonoSimpleBasicBlock **root, MonoMethod *method, MonoError *error)
{
int i;
int end = header->code_size;
error_init (error);
/*We must split at all points to verify for targets in the middle of an instruction*/
for (i = 0; i < header->num_clauses; ++i) {
MonoExceptionClause *clause = header->clauses + i;
MonoSimpleBasicBlock *try_block, *handler;
if (!(try_block = bb_split (bb, bb, root, clause->try_offset, TRUE, method, error)))
return;
handler = bb_split (bb, try_block, root, clause->handler_offset, FALSE, method, error);
if (!handler)
return;
handler->dead = FALSE;
if (clause->flags == MONO_EXCEPTION_CLAUSE_FILTER) {
MonoSimpleBasicBlock *filter = bb_split (bb, try_block, root, clause->data.filter_offset, FALSE, method, error);
if (!filter)
return;
filter->dead = FALSE;
}
if (clause->try_offset + clause->try_len < end && !bb_split (bb, try_block, root, clause->try_offset + clause->try_len, FALSE, method, error))
return;
if (clause->handler_offset + clause->handler_len < end && !bb_split (bb, handler, root, clause->handler_offset + clause->handler_len, FALSE, method, error))
return;
}
}
/*
* mono_basic_block_free:
*
* Release the memory associated with the list of basis blocks @bb.
*/
void
mono_basic_block_free (MonoSimpleBasicBlock *bb)
{
while (bb) {
MonoSimpleBasicBlock *next = bb->next;
if (bb->out_bb)
g_slist_free (bb->out_bb);
g_free (bb);
bb = next;
}
}
/*
* mono_basic_block_split:
*
* Return the list of basic blocks of method. Return NULL on failure and set @error.
*/
MonoSimpleBasicBlock*
mono_basic_block_split (MonoMethod *method, MonoError *error, MonoMethodHeader *header)
{
MonoSimpleBasicBlock *bb, *root;
const unsigned char *start, *end;
error_init (error);
start = header->code;
end = start + header->code_size;
bb = g_new0 (MonoSimpleBasicBlock, 1);
bb->start = 0;
bb->end = end - start;
bb->colour = BLACK;
bb->dead = FALSE;
root = bb;
bb_formation_il_pass (start, end, bb, &root, method, error);
if (!mono_error_ok (error))
goto fail;
bb_formation_eh_pass (header, bb, &root, method, error);
if (!mono_error_ok (error))
goto fail;
bb_liveness (bb);
#if DEBUG_BB
dump_bb_list (bb, &root, g_strdup_printf("AFTER LIVENESS %s", mono_method_full_name (method, TRUE)));
#endif
return bb;
fail:
mono_basic_block_free (bb);
return NULL;
}
/*
* mono_opcode_value_and_size:
*
* Returns the size of the opcode starting at *@ip, or -1 on error.
* Value is the opcode number.
*/
int
mono_opcode_value_and_size (const unsigned char **ip, const unsigned char *end, int *value)
{
const unsigned char *start = *ip, *p;
int i = *value = mono_opcode_value (ip, end);
int size = 0;
if (i < 0 || i >= MONO_CEE_LAST)
return -1;
p = *ip;
switch (mono_opcodes [i].argument) {
case MonoInlineNone:
size = 1;
break;
case MonoInlineString:
case MonoInlineType:
case MonoInlineField:
case MonoInlineMethod:
case MonoInlineTok:
case MonoInlineSig:
case MonoShortInlineR:
case MonoInlineI:
case MonoInlineBrTarget:
size = 5;
break;
case MonoInlineVar:
size = 3;
break;
case MonoShortInlineVar:
case MonoShortInlineI:
case MonoShortInlineBrTarget:
size = 2;
break;
case MonoInlineR:
case MonoInlineI8:
size = 9;
break;
case MonoInlineSwitch: {
guint32 entries;
if (ADDP_IS_GREATER_OR_OVF (p, 5, end))
return -1;
entries = read32 (p + 1);
if (entries >= (0xFFFFFFFFU / 4))
return -1;
size = 4 + 4 * entries;
break;
}
default:
g_error ("Invalid opcode %d argument %d max opcode %d\n", i, mono_opcodes [i].argument, MONO_CEE_LAST);
}
if (ADDP_IS_GREATER_OR_OVF (p, size, end))
return -1;
return (p - start) + size;
}
/*
* mono_opcode_size:
*
* Returns the size of the opcode starting at @ip, or -1 on error.
*/
int
mono_opcode_size (const unsigned char *ip, const unsigned char *end)
{
int tmp;
return mono_opcode_value_and_size (&ip, end, &tmp);
}