github
/
libjit
mirror of https://github.com/ademakov/libjit
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
Browse Source

reimplement optimization of relative instructions for the sake of correctness

cache-refactoring
Aleksey Demakov 18 years ago
parent
e002775c4a
commit
0adeff1a90
2 changed files with 141 additions and 247 deletions
Whitespace
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 10
      ChangeLog
  2. 350
      jit/jit-insn.c

10
ChangeLog
View File

@ -1,3 +1,11 @@
2007-06-11 Aleksey Demakov <ademakov@gmail.com>
* jit/jit-insn.c (accumulate_relative_offset): remove.
* jit/jit-insn.c (find_base_insn, jit_insn_load_relative)
(jit_insn_store_relative, jit_insn_add_relative): add find_base_insn
function that should finally optimize relative instructions
correctly.
2007-06-10 Aleksey Demakov <ademakov@gmail.com>
* tools/gen-rules-parser.y (gensel_output_clauses): alter selection
@ -597,7 +605,7 @@
and do not replace the accumulated instructions with JIT_OP_NOP as
it was before. The old approach is problematic because it is unknown
at this point if the values we accumulated are dead or they will be
used by instructions added later. The deadcode elimination pass
used by instructions added later. The dead code elimination pass
removes unused values just as well but with enough knowledge to be
safe. The new code also does not move JIT_OP_ADDRESS_OF towards the
relative instructions that uses the address. Supposedly such move

350
jit/jit-insn.c
View File

@ -1456,174 +1456,116 @@ int jit_insn_store(jit_function_t func, jit_value_t dest, jit_value_t value)
return 1;
}
#define ACCUMULATE_RELATIVE 1
#if !ACCUMULATE_RELATIVE
/*
* Scan back through the current block, looking for a relative adjustment
* that involves "value" as its destination. Returns NULL if no such
* instruction was found, or it is blocked by a later use of "value".
* "addrof" will be set to a non-NULL value if the instruction just before
* the relative adjustment took the address of a local frame variable.
* This instruction is a candidate for being moved down to where the
* "load_relative" or "store_relative" occurs.
* Scan back through the current block, looking for an address instruction that
* involves "value" as its destination. Returns NULL if no such instruction was
* found, or it is blocked by a later use of "value".
*
* The instruction found may then be combined into a new single instruction with
* the following "load_relative", "store_relative", or another "relative_add".
*
* For instance, consider the code like this:
*
* i) y = address_of(x)
* ...
* j) z = add_relative(y, a)
*
* Let's suppose that we need to add a "store_realtive(z, b, v)" instruction.
* The "find_base_insn()" call will return the instruction "j" and we will be
* able to emit the instruction "store_relative(y, a + b, v)" instead. If "z"
* is not used elsewhere then "j" will be optimized away by the dead code
* elimination pass.
*
* Repetitive use of this procedure for a chain of "add_relative" instructions
* converts it into a series of indpenedent instructions each using the very
* first address in the chain as its base. Therefore regardless of the initial
* chain length it is always enough to make single "find_base_insn()" call to
* get the base address of the entire chain (think induction).
*
* Note that in this situation the second "find_base_insn()" call will return
* the instruction "i" that obtains the base address as the address of a local
* frame variable. This instruction is a candidate for being moved down to
* where the "load_relative" or "store_relative" occurs. This might make it
* easier for the code generator to handle field accesses whitin local
* variables.
*
* The "plast" argument indicates if the found instruction is already the last
* one, so there is no need to move it down.
*/
static jit_insn_t previous_relative(jit_function_t func, jit_value_t value,
jit_insn_t *addrof)
static jit_insn_t
find_base_insn(
jit_function_t func,
jit_insn_iter_t iter,
jit_value_t value,
int *plast)
{
jit_insn_iter_t iter;
int last;
jit_insn_t insn;
jit_insn_iter_t iter2;
jit_insn_t insn2;
jit_insn_t insn3;
/* Clear "addrof" first */
*addrof = 0;
/* If the value is not temporary, then it isn't a candidate */
if(!(value->is_temporary))
/* The "value" could be vulnerable to aliasing effects so we cannot
optimize it */
if(value->is_addressable || value->is_volatile)
{
return 0;
}
/* Iterate back through the block looking for a suitable adjustment */
jit_insn_iter_init_last(&iter, func->builder->current_block);
/* We are about to check the last instruction before the current one */
last = 1;
/* Iterate back through the block looking for a suitable instruction */
while((insn = jit_insn_iter_previous(&iter)) != 0)
{
if(insn->opcode == JIT_OP_ADD_RELATIVE && insn->dest == value)
{
/* See if the instruction just before the "add_relative"
is an "address_of" that is being used by the add */
insn3 = jit_insn_iter_previous(&iter);
if(insn3)
/* This instruction uses "value" in some way */
if(insn->dest == value)
{
jit_insn_iter_next(&iter);
if(insn3->opcode != JIT_OP_ADDRESS_OF ||
insn3->dest != insn->value1 ||
!(insn3->dest->is_temporary))
/* This is the instruction we were looking for */
if(insn->opcode == JIT_OP_ADDRESS_OF)
{
insn3 = 0;
}
*plast = last;
return insn;
}
/* Scan forwards to ensure that "insn->value1" is not
used anywhere in the instructions that follow */
jit_insn_iter_next(&iter);
while((insn2 = jit_insn_iter_next(&iter)) != 0)
if(insn->opcode == JIT_OP_ADD_RELATIVE)
{
if(insn2->dest == insn->value1 ||
insn2->value1 == insn->value1 ||
insn2->value2 == insn->value1)
value = insn->value1;
if(value->is_addressable || value->is_volatile)
{
return 0;
}
if(insn3)
{
/* We may need to disable the "address_of" instruction
if any of its values are used further on */
if(insn2->dest == insn3->dest ||
insn2->value1 == insn3->dest ||
insn2->value2 == insn3->dest ||
insn2->dest == insn3->value1 ||
insn2->value1 == insn3->value1 ||
insn2->value2 == insn3->value1)
{
insn3 = 0;
}
}
}
if(insn3)
/* Scan forwards to ensure that "insn->value1"
is not modified anywhere in the instructions
that follow */
iter2 = iter;
jit_insn_iter_next(&iter2);
while((insn2 = jit_insn_iter_next(&iter2)) != 0)
{
*addrof = insn3;
}
return insn;
}
if(insn->dest == value || insn->value1 == value ||
insn->value2 == value)
if(insn2->dest == value
&& (insn2->flags & JIT_INSN_DEST_IS_VALUE) == 0)
{
/* This instruction uses "value" in some way, so it
blocks any previous "add_relative" instructions */
return 0;
}
}
return 0;
}
#else
static int
accumulate_relative_offset(
jit_function_t func,
jit_value_t value,
jit_nint offset,
jit_value_t *addrof_ptr,
jit_value_t *value_ptr,
jit_nint *offset_ptr)
{
jit_insn_iter_t iter;
jit_insn_t insn;
if(addrof_ptr)
{
*addrof_ptr = 0;
}
if(value_ptr)
{
*value_ptr = 0;
}
if(offset_ptr)
{
*offset_ptr = 0;
*plast = last;
return insn;
}
jit_insn_iter_init_last(&iter, func->builder->current_block);
while((insn = jit_insn_iter_previous(&iter)) != 0)
{
if(!(value->is_temporary))
{
break;
}
if(insn->dest != value)
{
continue;
}
if(insn->opcode == JIT_OP_ADDRESS_OF)
{
if(addrof_ptr)
{
*addrof_ptr = insn->value1;
}
break;
}
if(insn->opcode != JIT_OP_ADD_RELATIVE)
{
/* Oops. This instruction modifies "value" and blocks
any previous address_of or add_relative instructions */
if((insn->flags & JIT_INSN_DEST_IS_VALUE) == 0)
{
/* This instruction modifies "value" in some way,
so it blocks any previous "add_relative"
instructions */
return 0;
}
continue;
break;
}
offset += jit_value_get_nint_constant(insn->value2);
value = insn->value1;
}
if(value_ptr)
{
*value_ptr = value;
/* We are to check instructions that preceed the last one */
last = 0;
}
if(offset_ptr)
{
*offset_ptr = offset;
}
return 1;
return 0;
}
#endif
/*@
* @deftypefun jit_value_t jit_insn_load_relative (jit_function_t func, jit_value_t value, jit_nint offset, jit_type_t type)
* Load a value of the specified @code{type} from the effective address
@ -1634,14 +1576,10 @@ jit_value_t jit_insn_load_relative
(jit_function_t func, jit_value_t value,
jit_nint offset, jit_type_t type)
{
#if ACCUMULATE_RELATIVE
jit_value_t addrof;
jit_value_t new_value;
jit_nint new_offset;
#else
jit_insn_iter_t iter;
jit_insn_t insn;
jit_insn_t addrof;
#endif
int last;
if(!value)
{
return 0;
@ -1650,42 +1588,29 @@ jit_value_t jit_insn_load_relative
{
return 0;
}
#if ACCUMULATE_RELATIVE
if(accumulate_relative_offset(func, value, offset, &addrof, &new_value, &new_offset))
{
value = new_value;
offset = new_offset;
}
#else
insn = previous_relative(func, value, &addrof);
if(insn)
jit_insn_iter_init_last(&iter, func->builder->current_block);
insn = find_base_insn(func, iter, value, &last);
if(insn && insn->opcode == JIT_OP_ADD_RELATIVE)
{
/* We have a previous "add_relative" instruction for this
pointer. Remove it from the instruction stream and
adjust the current offset accordingly */
pointer. Adjust the current offset accordingly */
offset += jit_value_get_nint_constant(insn->value2);
value = insn->value1;
insn->opcode = JIT_OP_NOP;
insn->dest = 0;
insn->value1 = 0;
insn->value2 = 0;
if(addrof)
insn = find_base_insn(func, iter, value, &last);
last = 0;
}
if(insn && insn->opcode == JIT_OP_ADDRESS_OF && !last)
{
/* Shift the "address_of" instruction down too, to make
/* Shift the "address_of" instruction down, to make
it easier for the code generator to handle field
accesses within local and global variables */
value = jit_insn_address_of(func, addrof->value1);
value = jit_insn_address_of(func, insn->value1);
if(!value)
{
return 0;
}
addrof->opcode = JIT_OP_NOP;
addrof->dest = 0;
addrof->value1 = 0;
addrof->value2 = 0;
}
}
#endif
return apply_binary
(func, _jit_load_opcode(JIT_OP_LOAD_RELATIVE_SBYTE, type, 0, 0), value,
jit_value_create_nint_constant(func, jit_type_nint, offset), type);
@ -1701,15 +1626,11 @@ int jit_insn_store_relative
(jit_function_t func, jit_value_t dest,
jit_nint offset, jit_value_t value)
{
jit_insn_iter_t iter;
jit_insn_t insn;
int last;
jit_value_t offset_value;
#if ACCUMULATE_RELATIVE
jit_value_t addrof;
jit_value_t new_dest;
jit_nint new_offset;
#else
jit_insn_t addrof;
#endif
if(!dest || !value)
{
return 0;
@ -1718,42 +1639,30 @@ int jit_insn_store_relative
{
return 0;
}
#if ACCUMULATE_RELATIVE
if(accumulate_relative_offset(func, dest, offset, &addrof, &new_dest, &new_offset))
{
dest = new_dest;
offset = new_offset;
}
#else
insn = previous_relative(func, dest, &addrof);
if(insn)
jit_insn_iter_init_last(&iter, func->builder->current_block);
insn = find_base_insn(func, iter, dest, &last);
if(insn && insn->opcode == JIT_OP_ADD_RELATIVE)
{
/* We have a previous "add_relative" instruction for this
pointer. Remove it from the instruction stream and
adjust the current offset accordingly */
pointer. Adjust the current offset accordingly */
offset += jit_value_get_nint_constant(insn->value2);
dest = insn->value1;
insn->opcode = JIT_OP_NOP;
insn->dest = 0;
insn->value1 = 0;
insn->value2 = 0;
if(addrof)
insn = find_base_insn(func, iter, value, &last);
last = 0;
}
if(insn && insn->opcode == JIT_OP_ADDRESS_OF && !last)
{
/* Shift the "address_of" instruction down too, to make
/* Shift the "address_of" instruction down, to make
it easier for the code generator to handle field
accesses within local and global variables */
dest = jit_insn_address_of(func, addrof->value1);
dest = jit_insn_address_of(func, insn->value1);
if(!dest)
{
return 0;
}
addrof->opcode = JIT_OP_NOP;
addrof->dest = 0;
addrof->value1 = 0;
addrof->value2 = 0;
}
}
#endif
offset_value = jit_value_create_nint_constant(func, jit_type_nint, offset);
if(!offset_value)
{
@ -1766,8 +1675,7 @@ int jit_insn_store_relative
}
jit_value_ref(func, dest);
jit_value_ref(func, value);
insn->opcode = (short)_jit_store_opcode
(JIT_OP_STORE_RELATIVE_BYTE, 0, value->type);
insn->opcode = (short)_jit_store_opcode(JIT_OP_STORE_RELATIVE_BYTE, 0, value->type);
insn->flags = JIT_INSN_DEST_IS_VALUE;
insn->dest = dest;
insn->value1 = value;
@ -1788,28 +1696,10 @@ int jit_insn_store_relative
jit_value_t jit_insn_add_relative
(jit_function_t func, jit_value_t value, jit_nint offset)
{
#if ACCUMULATE_RELATIVE
jit_value_t new_value;
jit_nint new_offset;
if(!value)
{
return 0;
}
if(!_jit_function_ensure_builder(func))
{
return 0;
}
if(accumulate_relative_offset(func, value, offset, 0, &new_value, &new_offset))
{
value = new_value;
offset = new_offset;
}
return apply_binary(func, JIT_OP_ADD_RELATIVE, value,
jit_value_create_nint_constant(func, jit_type_nint, offset),
jit_type_void_ptr);
#else
jit_insn_iter_t iter;
jit_insn_t insn;
jit_insn_t addrof;
int last;
if(!value)
{
return 0;
@ -1818,24 +1708,20 @@ jit_value_t jit_insn_add_relative
{
return 0;
}
insn = previous_relative(func, value, &addrof);
if(insn)
jit_insn_iter_init_last(&iter, func->builder->current_block);
insn = find_base_insn(func, iter, value, &last);
if(insn && insn->opcode == JIT_OP_ADD_RELATIVE)
{
/* Back-patch the "add_relative" instruction to adjust the offset */
insn->value2 = jit_value_create_nint_constant
(func, jit_type_nint,
jit_value_get_nint_constant(insn->value2) + offset);
return value;
/* We have a previous "add_relative" instruction for this
pointer. Adjust the current offset accordingly */
offset += jit_value_get_nint_constant(insn->value2);
value = insn->value1;
}
else
{
/* Create a new "add_relative" instruction */
return apply_binary(func, JIT_OP_ADD_RELATIVE, value,
jit_value_create_nint_constant
(func, jit_type_nint, offset),
jit_value_create_nint_constant(func, jit_type_nint, offset),
jit_type_void_ptr);
}
#endif
}
/*@

Write Preview
Loading…
Cancel
Save