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cc-61.0.1
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explow.c
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1991-06-04
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/* Subroutines for manipulating rtx's in semantically interesting ways.
Copyright (C) 1987, 1990 Free Software Foundation, Inc.
This file is part of GNU CC.
GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "config.h"
#include "rtl.h"
#include "tree.h"
#include "flags.h"
#include "expr.h"
#include "hard-reg-set.h"
#include "insn-flags.h"
/* Return an rtx for the sum of X and the integer C. */
rtx
plus_constant (x, c)
register rtx x;
register int c;
{
register RTX_CODE code = GET_CODE (x);
register enum machine_mode mode = GET_MODE (x);
register rtx tem;
int all_constant = 0;
if (c == 0)
return x;
switch (code)
{
case CONST_INT:
return gen_rtx (CONST_INT, VOIDmode, (INTVAL (x) + c));
case CONST_DOUBLE:
{
int l1 = CONST_DOUBLE_LOW (x);
int h1 = CONST_DOUBLE_HIGH (x);
int l2 = c;
int h2 = c < 0 ? ~0 : 0;
int lv, hv;
add_double (l1, h1, l2, h2, &lv, &hv);
return immed_double_const (lv, hv, VOIDmode);
}
case MEM:
/* If this is a reference to the constant pool, try replacing it with
a reference to a new constant. If the resulting address isn't
valid, don't return it because we have no way to validize it. */
if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
{
tem
= force_const_mem (GET_MODE (x),
plus_constant (get_pool_constant (XEXP (x, 0)),
c));
if (memory_address_p (GET_MODE (tem), XEXP (tem, 0)))
return tem;
}
break;
case CONST:
/* If adding to something entirely constant, set a flag
so that we can add a CONST around the result. */
x = XEXP (x, 0);
all_constant = 1;
break;
case SYMBOL_REF:
case LABEL_REF:
all_constant = 1;
break;
case PLUS:
/* The interesting case is adding the integer to a sum.
Look for constant term in the sum and combine
with C. For an integer constant term, we make a combined
integer. For a constant term that is not an explicit integer,
we cannot really combine, but group them together anyway. */
if (GET_CODE (XEXP (x, 0)) == CONST_INT)
{
c += INTVAL (XEXP (x, 0));
x = XEXP (x, 1);
}
else if (GET_CODE (XEXP (x, 1)) == CONST_INT)
{
c += INTVAL (XEXP (x, 1));
x = XEXP (x, 0);
}
else if (CONSTANT_P (XEXP (x, 0)))
return gen_rtx (PLUS, mode,
plus_constant (XEXP (x, 0), c),
XEXP (x, 1));
else if (CONSTANT_P (XEXP (x, 1)))
return gen_rtx (PLUS, mode,
XEXP (x, 0),
plus_constant (XEXP (x, 1), c));
}
if (c != 0)
x = gen_rtx (PLUS, mode, x, gen_rtx (CONST_INT, VOIDmode, c));
if (GET_CODE (x) == SYMBOL_REF || GET_CODE (x) == LABEL_REF)
return x;
else if (all_constant)
return gen_rtx (CONST, mode, x);
else
return x;
}
/* This is the same a `plus_constant', except that it handles LO_SUM. */
rtx
plus_constant_for_output (x, c)
register rtx x;
register int c;
{
register RTX_CODE code = GET_CODE (x);
register enum machine_mode mode = GET_MODE (x);
int all_constant = 0;
if (GET_CODE (x) == LO_SUM)
return gen_rtx (LO_SUM, mode, XEXP (x, 0),
plus_constant_for_output (XEXP (x, 1), c));
else
return plus_constant (x, c);
}
/* If X is a sum, return a new sum like X but lacking any constant terms.
Add all the removed constant terms into *CONSTPTR.
X itself is not altered. The result != X if and only if
it is not isomorphic to X. */
rtx
eliminate_constant_term (x, constptr)
rtx x;
int *constptr;
{
int c;
register rtx x0, x1;
if (GET_CODE (x) != PLUS)
return x;
/* First handle constants appearing at this level explicitly. */
if (GET_CODE (XEXP (x, 0)) == CONST_INT)
{
*constptr += INTVAL (XEXP (x, 0));
return eliminate_constant_term (XEXP (x, 1), constptr);
}
if (GET_CODE (XEXP (x, 1)) == CONST_INT)
{
*constptr += INTVAL (XEXP (x, 1));
return eliminate_constant_term (XEXP (x, 0), constptr);
}
c = 0;
x0 = eliminate_constant_term (XEXP (x, 0), &c);
x1 = eliminate_constant_term (XEXP (x, 1), &c);
if (x1 != XEXP (x, 1) || x0 != XEXP (x, 0))
{
*constptr += c;
return gen_rtx (PLUS, GET_MODE (x), x0, x1);
}
return x;
}
/* Returns the insn that next references REG after INSN, or 0
if REG is clobbered before next referenced or we cannot find
an insn that references REG in a straight-line piece of code. */
rtx
find_next_ref (reg, insn)
rtx reg;
rtx insn;
{
rtx next;
for (insn = NEXT_INSN (insn); insn; insn = next)
{
next = NEXT_INSN (insn);
if (GET_CODE (insn) == NOTE)
continue;
if (GET_CODE (insn) == CODE_LABEL
|| GET_CODE (insn) == BARRIER)
return 0;
if (GET_CODE (insn) == INSN
|| GET_CODE (insn) == JUMP_INSN
|| GET_CODE (insn) == CALL_INSN)
{
if (reg_set_p (reg, PATTERN (insn)))
return 0;
if (reg_mentioned_p (reg, PATTERN (insn)))
return insn;
if (GET_CODE (insn) == JUMP_INSN)
{
if (simplejump_p (insn))
next = JUMP_LABEL (insn);
else
return 0;
}
if (GET_CODE (insn) == CALL_INSN
&& REGNO (reg) < FIRST_PSEUDO_REGISTER
&& call_used_regs[REGNO (reg)])
return 0;
}
else
abort ();
}
return 0;
}
/* Return an rtx for the size in bytes of the value of EXP. */
rtx
expr_size (exp)
tree exp;
{
return expand_expr (size_in_bytes (TREE_TYPE (exp)), 0, SImode, 0);
}
/* Return a copy of X in which all memory references
and all constants that involve symbol refs
have been replaced with new temporary registers.
Also emit code to load the memory locations and constants
into those registers.
If X contains no such constants or memory references,
X itself (not a copy) is returned.
If a constant is found in the address that is not a legitimate constant
in an insn, it is left alone in the hope that it might be valid in the
address.
X may contain no arithmetic except addition, subtraction and multiplication.
Values returned by expand_expr with 1 for sum_ok fit this constraint. */
static rtx
break_out_memory_refs (x)
register rtx x;
{
if (GET_CODE (x) == MEM
|| (CONSTANT_P (x) && LEGITIMATE_CONSTANT_P (x)
&& GET_MODE (x) != VOIDmode))
{
register rtx temp = force_reg (GET_MODE (x), x);
mark_reg_pointer (temp);
x = temp;
}
else if (GET_CODE (x) == PLUS || GET_CODE (x) == MINUS
|| GET_CODE (x) == MULT)
{
register rtx op0 = break_out_memory_refs (XEXP (x, 0));
register rtx op1 = break_out_memory_refs (XEXP (x, 1));
if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
x = gen_rtx (GET_CODE (x), Pmode, op0, op1);
}
return x;
}
/* Given a memory address or facsimile X, construct a new address,
currently equivalent, that is stable: future stores won't change it.
X must be composed of constants, register and memory references
combined with addition, subtraction and multiplication:
in other words, just what you can get from expand_expr if sum_ok is 1.
Works by making copies of all regs and memory locations used
by X and combining them the same way X does.
You could also stabilize the reference to this address
by copying the address to a register with copy_to_reg;
but then you wouldn't get indexed addressing in the reference. */
rtx
copy_all_regs (x)
register rtx x;
{
if (GET_CODE (x) == REG)
{
if (REGNO (x) != FRAME_POINTER_REGNUM)
x = copy_to_reg (x);
}
else if (GET_CODE (x) == MEM)
x = copy_to_reg (x);
else if (GET_CODE (x) == PLUS || GET_CODE (x) == MINUS
|| GET_CODE (x) == MULT)
{
register rtx op0 = copy_all_regs (XEXP (x, 0));
register rtx op1 = copy_all_regs (XEXP (x, 1));
if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
x = gen_rtx (GET_CODE (x), Pmode, op0, op1);
}
return x;
}
/* Return something equivalent to X but valid as a memory address
for something of mode MODE. When X is not itself valid, this
works by copying X or subexpressions of it into registers. */
rtx
memory_address (mode, x)
enum machine_mode mode;
register rtx x;
{
register rtx oldx;
/* By passing constant addresses thru registers
we get a chance to cse them. */
if (! cse_not_expected && CONSTANT_P (x) && LEGITIMATE_CONSTANT_P (x))
return force_reg (Pmode, x);
/* Accept a QUEUED that refers to a REG
even though that isn't a valid address.
On attempting to put this in an insn we will call protect_from_queue
which will turn it into a REG, which is valid. */
if (GET_CODE (x) == QUEUED
&& GET_CODE (QUEUED_VAR (x)) == REG)
return x;
/* We get better cse by rejecting indirect addressing at this stage.
Let the combiner create indirect addresses where appropriate.
For now, generate the code so that the subexpressions useful to share
are visible. But not if cse won't be done! */
oldx = x;
if (! cse_not_expected && GET_CODE (x) != REG)
x = break_out_memory_refs (x);
/* At this point, any valid address is accepted. */
GO_IF_LEGITIMATE_ADDRESS (mode, x, win);
/* If it was valid before but breaking out memory refs invalidated it,
use it the old way. */
if (memory_address_p (mode, oldx))
goto win2;
/* Perform machine-dependent transformations on X
in certain cases. This is not necessary since the code
below can handle all possible cases, but machine-dependent
transformations can make better code. */
LEGITIMIZE_ADDRESS (x, oldx, mode, win);
/* PLUS and MULT can appear in special ways
as the result of attempts to make an address usable for indexing.
Usually they are dealt with by calling force_operand, below.
But a sum containing constant terms is special
if removing them makes the sum a valid address:
then we generate that address in a register
and index off of it. We do this because it often makes
shorter code, and because the addresses thus generated
in registers often become common subexpressions. */
if (GET_CODE (x) == PLUS)
{
int constant_term = 0;
rtx y = eliminate_constant_term (x, &constant_term);
if (constant_term == 0
|| ! memory_address_p (mode, y))
return force_operand (x, 0);
y = plus_constant (copy_to_reg (y), constant_term);
if (! memory_address_p (mode, y))
return force_operand (x, 0);
return y;
}
if (GET_CODE (x) == MULT || GET_CODE (x) == MINUS)
return force_operand (x, 0);
/* If we have a register that's an invalid address,
it must be a hard reg of the wrong class. Copy it to a pseudo. */
if (GET_CODE (x) == REG)
return copy_to_reg (x);
/* Last resort: copy the value to a register, since
the register is a valid address. */
return force_reg (Pmode, x);
win2:
x = oldx;
win:
if (flag_force_addr && ! cse_not_expected && GET_CODE (x) != REG
/* Don't copy an addr via a reg if it is one of our stack slots. */
&& ! (GET_CODE (x) == PLUS
&& (XEXP (x, 0) == virtual_stack_vars_rtx
|| XEXP (x, 0) == virtual_incoming_args_rtx)))
{
if (general_operand (x, Pmode))
return force_reg (Pmode, x);
else
return force_operand (x, 0);
}
return x;
}
/* Like `memory_address' but pretend `flag_force_addr' is 0. */
rtx
memory_address_noforce (mode, x)
enum machine_mode mode;
rtx x;
{
int ambient_force_addr = flag_force_addr;
rtx val;
flag_force_addr = 0;
val = memory_address (mode, x);
flag_force_addr = ambient_force_addr;
return val;
}
/* Convert a mem ref into one with a valid memory address.
Pass through anything else unchanged. */
rtx
validize_mem (ref)
rtx ref;
{
if (GET_CODE (ref) != MEM)
return ref;
if (memory_address_p (GET_MODE (ref), XEXP (ref, 0)))
return ref;
/* Don't alter REF itself, since that is probably a stack slot. */
return change_address (ref, GET_MODE (ref), XEXP (ref, 0));
}
/* Return a modified copy of X with its memory address copied
into a temporary register to protect it from side effects.
If X is not a MEM, it is returned unchanged (and not copied).
Perhaps even if it is a MEM, if there is no need to change it. */
rtx
stabilize (x)
rtx x;
{
register rtx addr;
if (GET_CODE (x) != MEM)
return x;
addr = XEXP (x, 0);
if (rtx_unstable_p (addr))
{
rtx temp = copy_all_regs (addr);
rtx mem;
if (GET_CODE (temp) != REG)
temp = copy_to_reg (temp);
mem = gen_rtx (MEM, GET_MODE (x), temp);
/* Mark returned memref with in_struct
if it's in an array or structure. */
if (GET_CODE (addr) == PLUS || MEM_IN_STRUCT_P (x))
MEM_IN_STRUCT_P (mem) = 1;
return mem;
}
return x;
}
/* Copy the value or contents of X to a new temp reg and return that reg. */
rtx
copy_to_reg (x)
rtx x;
{
register rtx temp = gen_reg_rtx (GET_MODE (x));
/* If not an operand, must be an address with PLUS and MULT so
do the computation. */
if (! general_operand (x, VOIDmode))
x = force_operand (x, temp);
if (x != temp)
emit_move_insn (temp, x);
return temp;
}
/* Like copy_to_reg but always give the new register mode Pmode
in case X is a constant. */
rtx
copy_addr_to_reg (x)
rtx x;
{
return copy_to_mode_reg (Pmode, x);
}
/* Like copy_to_reg but always give the new register mode MODE
in case X is a constant. */
rtx
copy_to_mode_reg (mode, x)
enum machine_mode mode;
rtx x;
{
register rtx temp = gen_reg_rtx (mode);
/* If not an operand, must be an address with PLUS and MULT so
do the computation. */
if (! general_operand (x, VOIDmode))
x = force_operand (x, temp);
if (GET_MODE (x) != mode && GET_MODE (x) != VOIDmode)
abort ();
if (x != temp)
emit_move_insn (temp, x);
return temp;
}
/* Load X into a register if it is not already one.
Use mode MODE for the register.
X should be valid for mode MODE, but it may be a constant which
is valid for all integer modes; that's why caller must specify MODE.
The caller must not alter the value in the register we return,
since we mark it as a "constant" register. */
rtx
force_reg (mode, x)
enum machine_mode mode;
rtx x;
{
register rtx temp, insn;
if (GET_CODE (x) == REG)
return x;
temp = gen_reg_rtx (mode);
insn = emit_move_insn (temp, x);
/* Let optimizers know that TEMP's value never changes
and that X can be substituted for it. */
if (CONSTANT_P (x))
{
rtx note = find_reg_note (insn, REG_EQUAL, 0);
if (note)
XEXP (note, 0) = x;
else
REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_EQUAL, x, REG_NOTES (insn));
}
return temp;
}
/* If X is a memory ref, copy its contents to a new temp reg and return
that reg. Otherwise, return X. */
rtx
force_not_mem (x)
rtx x;
{
register rtx temp;
if (GET_CODE (x) != MEM || GET_MODE (x) == BLKmode)
return x;
temp = gen_reg_rtx (GET_MODE (x));
emit_move_insn (temp, x);
return temp;
}
/* Copy X to TARGET (if it's nonzero and a reg)
or to a new temp reg and return that reg. */
rtx
copy_to_suggested_reg (x, target)
rtx x, target;
{
register rtx temp;
if (target && GET_CODE (target) == REG)
temp = target;
else
temp = gen_reg_rtx (GET_MODE (x));
emit_move_insn (temp, x);
return temp;
}
/* Adjust the stack pointer by ADJUST (an rtx for a number of bytes).
This pops when ADJUST is positive. ADJUST need not be constant. */
void
adjust_stack (adjust)
rtx adjust;
{
rtx temp;
adjust = protect_from_queue (adjust, 0);
if (adjust == const0_rtx)
return;
temp = expand_binop (Pmode,
#ifdef STACK_GROWS_DOWNWARD
add_optab,
#else
sub_optab,
#endif
stack_pointer_rtx, adjust, stack_pointer_rtx, 0,
OPTAB_LIB_WIDEN);
if (temp != stack_pointer_rtx)
emit_move_insn (stack_pointer_rtx, temp);
}
/* Adjust the stack pointer by minus ADJUST (an rtx for a number of bytes).
This pushes when ADJUST is positive. ADJUST need not be constant. */
void
anti_adjust_stack (adjust)
rtx adjust;
{
rtx temp;
adjust = protect_from_queue (adjust, 0);
if (adjust == const0_rtx)
return;
temp = expand_binop (Pmode,
#ifdef STACK_GROWS_DOWNWARD
sub_optab,
#else
add_optab,
#endif
stack_pointer_rtx, adjust, stack_pointer_rtx, 0,
OPTAB_LIB_WIDEN);
if (temp != stack_pointer_rtx)
emit_move_insn (stack_pointer_rtx, temp);
}
/* Round the size of a block to be pushed up to the boundary required
by this machine. SIZE is the desired size, which need not be constant. */
rtx
round_push (size)
rtx size;
{
#ifdef STACK_BOUNDARY
int align = STACK_BOUNDARY / BITS_PER_UNIT;
if (align == 1)
return size;
if (GET_CODE (size) == CONST_INT)
{
int new = (INTVAL (size) + align - 1) / align * align;
if (INTVAL (size) != new)
size = gen_rtx (CONST_INT, VOIDmode, new);
}
else
{
size = expand_divmod (0, CEIL_DIV_EXPR, Pmode, size,
gen_rtx (CONST_INT, VOIDmode, align),
0, 1);
size = expand_mult (Pmode, size,
gen_rtx (CONST_INT, VOIDmode, align),
0, 1);
}
#endif /* STACK_BOUNDARY */
return size;
}
/* Return an rtx representing the address of an area of memory dynamically
pushed on the stack. Any required rounding is done.
SIZE is an rtx representing the size of the area.
TARGET is a place in which the address can be placed. */
rtx
allocate_dynamic_stack_space (size, target)
rtx size;
rtx target;
{
#ifdef STACK_POINTER_OFFSET
int misalignment
= STACK_POINTER_OFFSET % (BIGGEST_ALIGNMENT / BITS_PER_WORD);
int compensation = (BIGGEST_ALIGNMENT / BITS_PER_WORD) - misalignment;
#else
int misalignment = 0, compensation = 0;
#endif
/* Ensure the size is in a register and is the proper mode. */
if (! CONSTANT_P (size))
{
size = force_reg (GET_MODE (size), size);
if (GET_MODE (size) != Pmode)
size = convert_to_mode (Pmode, size, 1);
}
#ifdef STACK_POINTER_OFFSET
/* Compensate for any lack of alignment of the storage
to actually be used. */
if (misalignment != 0)
size = plus_constant (size, compensation);
#endif
do_pending_stack_adjust ();
#ifdef STACK_GROWS_DOWNWARD
#ifdef STACK_BOUNDARY
#define STACK_ALIGNMENT (STACK_BOUNDARY / BITS_PER_UNIT)
#else
#define STACK_ALIGNMENT 1
#endif
/* An important special-case is where the stack grows downward and where
we either do not have a stack offset or the stack offset is a multiple
of the alignment amount (if it isn't we don't know whether the actual
sp value or the virtual top of stack is what is to be aligned, so
we just assume it started aligned and align the amount to push). In
that case, aligning the stack pointer value rather than the size to
push will save one insn. */
if (exact_log2 (STACK_ALIGNMENT) >= 0
&& (target == 0 || GET_CODE (target) == REG)
#ifdef STACK_POINTER_OFFSET
&& STACK_POINTER_OFFSET % STACK_ALIGNMENT == 0
#endif
)
{
anti_adjust_stack (size);
if (STACK_ALIGNMENT != 1)
{
rtx temp = expand_binop (Pmode, and_optab, stack_pointer_rtx,
gen_rtx (CONST_INT, VOIDmode,
~ (STACK_ALIGNMENT - 1)),
stack_pointer_rtx, 0, OPTAB_LIB_WIDEN);
if (temp != stack_pointer_rtx)
emit_move_insn (stack_pointer_rtx, temp);
}
}
else
anti_adjust_stack (round_push (size));
#endif
/* Return a copy of current stack ptr in TARGET. */
if (target == 0)
target = gen_reg_rtx (Pmode);
#ifdef STACK_POINTER_OFFSET
/* Compensate for any lack of alignment of the storage to actually
be used, by skipping ahead to an aligned address. */
if (misalignment)
{
rtx temp = expand_binop (Pmode, add_optab, target,
gen_rtx (CONST_INT, VOIDmode, compensation),
stack_pointer_rtx, 0, OPTAB_LIB_WIDEN);
if (temp != target)
emit_move_insn (target, temp);
}
else
#endif
emit_move_insn (target, virtual_stack_dynamic_rtx);
#ifndef STACK_GROWS_DOWNWARD
anti_adjust_stack (round_push (size));
#endif
/* Some systems require a particular insn to refer to the stack
to make the pages exist or to format the bottom of the stack
in some particular way. */
#ifdef HAVE_probe
if (HAVE_probe)
emit_insn (gen_probe (size));
#endif
return target;
}
/* Return an rtx representing the register or memory location
in which a scalar value of data type VALTYPE
was returned by a function call to function FUNC.
FUNC is a FUNCTION_DECL node if the precise function is known,
otherwise 0. */
rtx
hard_function_value (valtype, func)
tree valtype;
tree func;
{
return FUNCTION_VALUE (valtype, func);
}
/* Return an rtx representing the register or memory location
in which a scalar value of mode MODE was returned by a library call. */
rtx
hard_libcall_value (mode)
enum machine_mode mode;
{
return LIBCALL_VALUE (mode);
}