- /* Include declared information about alignment of pointers. */
- /* ??? We don't properly preserve REG_POINTER changes across
- pointer-to-integer casts, so we can't trust it except for
- things that we know must be pointers. See execute/960116-1.c. */
- if ((x == stack_pointer_rtx
- || x == frame_pointer_rtx
- || x == arg_pointer_rtx)
- && REGNO_POINTER_ALIGN (REGNO (x)))
- {
- unsigned HOST_WIDE_INT alignment
- = REGNO_POINTER_ALIGN (REGNO (x)) / BITS_PER_UNIT;
-
-#ifdef PUSH_ROUNDING
- /* If PUSH_ROUNDING is defined, it is possible for the
- stack to be momentarily aligned only to that amount,
- so we pick the least alignment. */
- if (x == stack_pointer_rtx && PUSH_ARGS)
- alignment = MIN ((unsigned HOST_WIDE_INT) PUSH_ROUNDING (1),
- alignment);
-#endif
-
- nonzero &= ~(alignment - 1);
- }
-
- /* If X is a register whose nonzero bits value is current, use it.
- Otherwise, if X is a register whose value we can find, use that
- value. Otherwise, use the previously-computed global nonzero bits
- for this register. */
-
- if (reg_last_set_value[REGNO (x)] != 0
- && (reg_last_set_mode[REGNO (x)] == mode
- || (GET_MODE_CLASS (reg_last_set_mode[REGNO (x)]) == MODE_INT
- && GET_MODE_CLASS (mode) == MODE_INT))
- && (reg_last_set_label[REGNO (x)] == label_tick
- || (REGNO (x) >= FIRST_PSEUDO_REGISTER
- && REG_N_SETS (REGNO (x)) == 1
- && ! REGNO_REG_SET_P (ENTRY_BLOCK_PTR->next_bb->global_live_at_start,
- REGNO (x))))
- && INSN_CUID (reg_last_set[REGNO (x)]) < subst_low_cuid)
- return reg_last_set_nonzero_bits[REGNO (x)] & nonzero;
-
- tem = get_last_value (x);
-
- if (tem)
- {
-#ifdef SHORT_IMMEDIATES_SIGN_EXTEND
- /* If X is narrower than MODE and TEM is a non-negative
- constant that would appear negative in the mode of X,
- sign-extend it for use in reg_nonzero_bits because some
- machines (maybe most) will actually do the sign-extension
- and this is the conservative approach.
-
- ??? For 2.5, try to tighten up the MD files in this regard
- instead of this kludge. */
-
- if (GET_MODE_BITSIZE (GET_MODE (x)) < mode_width
- && GET_CODE (tem) == CONST_INT
- && INTVAL (tem) > 0
- && 0 != (INTVAL (tem)
- & ((HOST_WIDE_INT) 1
- << (GET_MODE_BITSIZE (GET_MODE (x)) - 1))))
- tem = GEN_INT (INTVAL (tem)
- | ((HOST_WIDE_INT) (-1)
- << GET_MODE_BITSIZE (GET_MODE (x))));
-#endif
- return nonzero_bits_with_known (tem, mode) & nonzero;
- }
- else if (nonzero_sign_valid && reg_nonzero_bits[REGNO (x)])
- {
- unsigned HOST_WIDE_INT mask = reg_nonzero_bits[REGNO (x)];
-
- if (GET_MODE_BITSIZE (GET_MODE (x)) < mode_width)
- /* We don't know anything about the upper bits. */
- mask |= GET_MODE_MASK (mode) ^ GET_MODE_MASK (GET_MODE (x));
- return nonzero & mask;
- }
- else
- return nonzero;
-
- case CONST_INT:
-#ifdef SHORT_IMMEDIATES_SIGN_EXTEND
- /* If X is negative in MODE, sign-extend the value. */
- if (INTVAL (x) > 0 && mode_width < BITS_PER_WORD
- && 0 != (INTVAL (x) & ((HOST_WIDE_INT) 1 << (mode_width - 1))))
- return (INTVAL (x) | ((HOST_WIDE_INT) (-1) << mode_width));
-#endif
-
- return INTVAL (x);
-
- case MEM:
-#ifdef LOAD_EXTEND_OP
- /* In many, if not most, RISC machines, reading a byte from memory
- zeros the rest of the register. Noticing that fact saves a lot
- of extra zero-extends. */
- if (LOAD_EXTEND_OP (GET_MODE (x)) == ZERO_EXTEND)
- nonzero &= GET_MODE_MASK (GET_MODE (x));
-#endif
- break;
-
- case EQ: case NE:
- case UNEQ: case LTGT:
- case GT: case GTU: case UNGT:
- case LT: case LTU: case UNLT:
- case GE: case GEU: case UNGE:
- case LE: case LEU: case UNLE:
- case UNORDERED: case ORDERED:
-
- /* If this produces an integer result, we know which bits are set.
- Code here used to clear bits outside the mode of X, but that is
- now done above. */
-
- if (GET_MODE_CLASS (mode) == MODE_INT
- && mode_width <= HOST_BITS_PER_WIDE_INT)
- nonzero = STORE_FLAG_VALUE;
- break;
-
- case NEG:
-#if 0
- /* Disabled to avoid exponential mutual recursion between nonzero_bits
- and num_sign_bit_copies. */
- if (num_sign_bit_copies (XEXP (x, 0), GET_MODE (x))
- == GET_MODE_BITSIZE (GET_MODE (x)))
- nonzero = 1;
-#endif
-
- if (GET_MODE_SIZE (GET_MODE (x)) < mode_width)
- nonzero |= (GET_MODE_MASK (mode) & ~GET_MODE_MASK (GET_MODE (x)));
- break;
-
- case ABS:
-#if 0
- /* Disabled to avoid exponential mutual recursion between nonzero_bits
- and num_sign_bit_copies. */
- if (num_sign_bit_copies (XEXP (x, 0), GET_MODE (x))
- == GET_MODE_BITSIZE (GET_MODE (x)))
- nonzero = 1;
-#endif
- break;
-
- case TRUNCATE:
- nonzero &= (nonzero_bits_with_known (XEXP (x, 0), mode)
- & GET_MODE_MASK (mode));
- break;
-
- case ZERO_EXTEND:
- nonzero &= nonzero_bits_with_known (XEXP (x, 0), mode);
- if (GET_MODE (XEXP (x, 0)) != VOIDmode)
- nonzero &= GET_MODE_MASK (GET_MODE (XEXP (x, 0)));
- break;
-
- case SIGN_EXTEND:
- /* If the sign bit is known clear, this is the same as ZERO_EXTEND.
- Otherwise, show all the bits in the outer mode but not the inner
- may be nonzero. */
- inner_nz = nonzero_bits_with_known (XEXP (x, 0), mode);
- if (GET_MODE (XEXP (x, 0)) != VOIDmode)
- {
- inner_nz &= GET_MODE_MASK (GET_MODE (XEXP (x, 0)));
- if (inner_nz
- & (((HOST_WIDE_INT) 1
- << (GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0))) - 1))))
- inner_nz |= (GET_MODE_MASK (mode)
- & ~GET_MODE_MASK (GET_MODE (XEXP (x, 0))));
- }
-
- nonzero &= inner_nz;
- break;
-
- case AND:
- nonzero &= (nonzero_bits_with_known (XEXP (x, 0), mode)
- & nonzero_bits_with_known (XEXP (x, 1), mode));
- break;
-
- case XOR: case IOR:
- case UMIN: case UMAX: case SMIN: case SMAX:
- {
- unsigned HOST_WIDE_INT nonzero0 =
- nonzero_bits_with_known (XEXP (x, 0), mode);
-
- /* Don't call nonzero_bits for the second time if it cannot change
- anything. */
- if ((nonzero & nonzero0) != nonzero)
- nonzero &= (nonzero0
- | nonzero_bits_with_known (XEXP (x, 1), mode));
- }
- break;
-
- case PLUS: case MINUS:
- case MULT:
- case DIV: case UDIV:
- case MOD: case UMOD:
- /* We can apply the rules of arithmetic to compute the number of
- high- and low-order zero bits of these operations. We start by
- computing the width (position of the highest-order nonzero bit)
- and the number of low-order zero bits for each value. */
- {
- unsigned HOST_WIDE_INT nz0 =
- nonzero_bits_with_known (XEXP (x, 0), mode);
- unsigned HOST_WIDE_INT nz1 =
- nonzero_bits_with_known (XEXP (x, 1), mode);
- int sign_index = GET_MODE_BITSIZE (GET_MODE (x)) - 1;
- int width0 = floor_log2 (nz0) + 1;
- int width1 = floor_log2 (nz1) + 1;
- int low0 = floor_log2 (nz0 & -nz0);
- int low1 = floor_log2 (nz1 & -nz1);
- HOST_WIDE_INT op0_maybe_minusp
- = (nz0 & ((HOST_WIDE_INT) 1 << sign_index));
- HOST_WIDE_INT op1_maybe_minusp
- = (nz1 & ((HOST_WIDE_INT) 1 << sign_index));
- unsigned int result_width = mode_width;
- int result_low = 0;
-
- switch (code)
- {
- case PLUS:
- result_width = MAX (width0, width1) + 1;
- result_low = MIN (low0, low1);
- break;
- case MINUS:
- result_low = MIN (low0, low1);
- break;
- case MULT:
- result_width = width0 + width1;
- result_low = low0 + low1;
- break;
- case DIV:
- if (width1 == 0)
- break;
- if (! op0_maybe_minusp && ! op1_maybe_minusp)
- result_width = width0;
- break;
- case UDIV:
- if (width1 == 0)
- break;
- result_width = width0;
- break;
- case MOD:
- if (width1 == 0)
- break;
- if (! op0_maybe_minusp && ! op1_maybe_minusp)
- result_width = MIN (width0, width1);
- result_low = MIN (low0, low1);
- break;
- case UMOD:
- if (width1 == 0)
- break;
- result_width = MIN (width0, width1);
- result_low = MIN (low0, low1);
- break;
- default:
- abort ();
- }
-
- if (result_width < mode_width)
- nonzero &= ((HOST_WIDE_INT) 1 << result_width) - 1;
-
- if (result_low > 0)
- nonzero &= ~(((HOST_WIDE_INT) 1 << result_low) - 1);
-
-#ifdef POINTERS_EXTEND_UNSIGNED
- /* If pointers extend unsigned and this is an addition or subtraction
- to a pointer in Pmode, all the bits above ptr_mode are known to be
- zero. */
- if (POINTERS_EXTEND_UNSIGNED > 0 && GET_MODE (x) == Pmode
- && (code == PLUS || code == MINUS)
- && GET_CODE (XEXP (x, 0)) == REG && REG_POINTER (XEXP (x, 0)))
- nonzero &= GET_MODE_MASK (ptr_mode);
-#endif
- }
- break;
-
- case ZERO_EXTRACT:
- if (GET_CODE (XEXP (x, 1)) == CONST_INT
- && INTVAL (XEXP (x, 1)) < HOST_BITS_PER_WIDE_INT)
- nonzero &= ((HOST_WIDE_INT) 1 << INTVAL (XEXP (x, 1))) - 1;
- break;
-
- case SUBREG:
- /* If this is a SUBREG formed for a promoted variable that has
- been zero-extended, we know that at least the high-order bits
- are zero, though others might be too. */
-
- if (SUBREG_PROMOTED_VAR_P (x) && SUBREG_PROMOTED_UNSIGNED_P (x) > 0)
- nonzero = (GET_MODE_MASK (GET_MODE (x))
- & nonzero_bits_with_known (SUBREG_REG (x), GET_MODE (x)));
-
- /* If the inner mode is a single word for both the host and target
- machines, we can compute this from which bits of the inner
- object might be nonzero. */
- if (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) <= BITS_PER_WORD
- && (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x)))
- <= HOST_BITS_PER_WIDE_INT))
- {
- nonzero &= nonzero_bits_with_known (SUBREG_REG (x), mode);
-
-#if defined (WORD_REGISTER_OPERATIONS) && defined (LOAD_EXTEND_OP)
- /* If this is a typical RISC machine, we only have to worry
- about the way loads are extended. */
- if ((LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (x))) == SIGN_EXTEND
- ? (((nonzero
- & (((unsigned HOST_WIDE_INT) 1
- << (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) - 1))))
- != 0))
- : LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (x))) != ZERO_EXTEND)
- || GET_CODE (SUBREG_REG (x)) != MEM)
-#endif
- {
- /* On many CISC machines, accessing an object in a wider mode
- causes the high-order bits to become undefined. So they are
- not known to be zero. */
- if (GET_MODE_SIZE (GET_MODE (x))
- > GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
- nonzero |= (GET_MODE_MASK (GET_MODE (x))
- & ~GET_MODE_MASK (GET_MODE (SUBREG_REG (x))));
- }
- }
- break;
-
- case ASHIFTRT:
- case LSHIFTRT:
- case ASHIFT:
- case ROTATE:
- /* The nonzero bits are in two classes: any bits within MODE
- that aren't in GET_MODE (x) are always significant. The rest of the
- nonzero bits are those that are significant in the operand of
- the shift when shifted the appropriate number of bits. This
- shows that high-order bits are cleared by the right shift and
- low-order bits by left shifts. */
- if (GET_CODE (XEXP (x, 1)) == CONST_INT
- && INTVAL (XEXP (x, 1)) >= 0
- && INTVAL (XEXP (x, 1)) < HOST_BITS_PER_WIDE_INT)
- {
- enum machine_mode inner_mode = GET_MODE (x);
- unsigned int width = GET_MODE_BITSIZE (inner_mode);
- int count = INTVAL (XEXP (x, 1));
- unsigned HOST_WIDE_INT mode_mask = GET_MODE_MASK (inner_mode);
- unsigned HOST_WIDE_INT op_nonzero =
- nonzero_bits_with_known (XEXP (x, 0), mode);
- unsigned HOST_WIDE_INT inner = op_nonzero & mode_mask;
- unsigned HOST_WIDE_INT outer = 0;
-
- if (mode_width > width)
- outer = (op_nonzero & nonzero & ~mode_mask);
-
- if (code == LSHIFTRT)
- inner >>= count;
- else if (code == ASHIFTRT)
- {
- inner >>= count;
-
- /* If the sign bit may have been nonzero before the shift, we
- need to mark all the places it could have been copied to
- by the shift as possibly nonzero. */
- if (inner & ((HOST_WIDE_INT) 1 << (width - 1 - count)))
- inner |= (((HOST_WIDE_INT) 1 << count) - 1) << (width - count);
- }
- else if (code == ASHIFT)
- inner <<= count;
- else
- inner = ((inner << (count % width)
- | (inner >> (width - (count % width)))) & mode_mask);
-
- nonzero &= (outer | inner);
- }
- break;
-
- case FFS:
- case POPCOUNT:
- /* This is at most the number of bits in the mode. */
- nonzero = ((HOST_WIDE_INT) 2 << (floor_log2 (mode_width))) - 1;
- break;
-
- case CLZ:
- /* If CLZ has a known value at zero, then the nonzero bits are
- that value, plus the number of bits in the mode minus one. */
- if (CLZ_DEFINED_VALUE_AT_ZERO (mode, nonzero))
- nonzero |= ((HOST_WIDE_INT) 1 << (floor_log2 (mode_width))) - 1;
- else
- nonzero = -1;
- break;
-
- case CTZ:
- /* If CTZ has a known value at zero, then the nonzero bits are
- that value, plus the number of bits in the mode minus one. */
- if (CTZ_DEFINED_VALUE_AT_ZERO (mode, nonzero))
- nonzero |= ((HOST_WIDE_INT) 1 << (floor_log2 (mode_width))) - 1;
- else
- nonzero = -1;
- break;
-
- case PARITY:
- nonzero = 1;
- break;
-
- case IF_THEN_ELSE:
- nonzero &= (nonzero_bits_with_known (XEXP (x, 1), mode)
- | nonzero_bits_with_known (XEXP (x, 2), mode));
- break;
-
- default:
- break;
- }
-
- return nonzero;
-}
-
-/* See the macro definition above. */
-#undef cached_num_sign_bit_copies
-\f
-#define num_sign_bit_copies_with_known(X, M) \
- cached_num_sign_bit_copies (X, M, known_x, known_mode, known_ret)
-
-/* The function cached_num_sign_bit_copies is a wrapper around
- num_sign_bit_copies1. It avoids exponential behavior in
- num_sign_bit_copies1 when X has identical subexpressions on the
- first or the second level. */
-
-static unsigned int
-cached_num_sign_bit_copies (rtx x, enum machine_mode mode, rtx known_x,
- enum machine_mode known_mode,
- unsigned int known_ret)
-{
- if (x == known_x && mode == known_mode)
- return known_ret;
-
- /* Try to find identical subexpressions. If found call
- num_sign_bit_copies1 on X with the subexpressions as KNOWN_X and
- the precomputed value for the subexpression as KNOWN_RET. */
-
- if (GET_RTX_CLASS (GET_CODE (x)) == '2'
- || GET_RTX_CLASS (GET_CODE (x)) == 'c')
- {
- rtx x0 = XEXP (x, 0);
- rtx x1 = XEXP (x, 1);
-
- /* Check the first level. */
- if (x0 == x1)
- return
- num_sign_bit_copies1 (x, mode, x0, mode,
- num_sign_bit_copies_with_known (x0, mode));
-
- /* Check the second level. */
- if ((GET_RTX_CLASS (GET_CODE (x0)) == '2'
- || GET_RTX_CLASS (GET_CODE (x0)) == 'c')
- && (x1 == XEXP (x0, 0) || x1 == XEXP (x0, 1)))
- return
- num_sign_bit_copies1 (x, mode, x1, mode,
- num_sign_bit_copies_with_known (x1, mode));
-
- if ((GET_RTX_CLASS (GET_CODE (x1)) == '2'
- || GET_RTX_CLASS (GET_CODE (x1)) == 'c')
- && (x0 == XEXP (x1, 0) || x0 == XEXP (x1, 1)))
- return
- num_sign_bit_copies1 (x, mode, x0, mode,
- num_sign_bit_copies_with_known (x0, mode));
- }
-
- return num_sign_bit_copies1 (x, mode, known_x, known_mode, known_ret);
-}
-
-/* Return the number of bits at the high-order end of X that are known to
- be equal to the sign bit. X will be used in mode MODE; if MODE is
- VOIDmode, X will be used in its own mode. The returned value will always
- be between 1 and the number of bits in MODE. */
-
-static unsigned int
-num_sign_bit_copies1 (rtx x, enum machine_mode mode, rtx known_x,
- enum machine_mode known_mode,
- unsigned int known_ret)
-{
- enum rtx_code code = GET_CODE (x);
- unsigned int bitwidth;
- int num0, num1, result;
- unsigned HOST_WIDE_INT nonzero;
- rtx tem;
-
- /* If we weren't given a mode, use the mode of X. If the mode is still
- VOIDmode, we don't know anything. Likewise if one of the modes is
- floating-point. */
-
- if (mode == VOIDmode)
- mode = GET_MODE (x);
-
- if (mode == VOIDmode || FLOAT_MODE_P (mode) || FLOAT_MODE_P (GET_MODE (x)))
- return 1;
-
- bitwidth = GET_MODE_BITSIZE (mode);
-
- /* For a smaller object, just ignore the high bits. */
- if (bitwidth < GET_MODE_BITSIZE (GET_MODE (x)))
- {
- num0 = num_sign_bit_copies_with_known (x, GET_MODE (x));
- return MAX (1,
- num0 - (int) (GET_MODE_BITSIZE (GET_MODE (x)) - bitwidth));
- }
-
- if (GET_MODE (x) != VOIDmode && bitwidth > GET_MODE_BITSIZE (GET_MODE (x)))
- {
-#ifndef WORD_REGISTER_OPERATIONS
- /* If this machine does not do all register operations on the entire
- register and MODE is wider than the mode of X, we can say nothing
- at all about the high-order bits. */
- return 1;
-#else
- /* Likewise on machines that do, if the mode of the object is smaller
- than a word and loads of that size don't sign extend, we can say
- nothing about the high order bits. */
- if (GET_MODE_BITSIZE (GET_MODE (x)) < BITS_PER_WORD
-#ifdef LOAD_EXTEND_OP
- && LOAD_EXTEND_OP (GET_MODE (x)) != SIGN_EXTEND
-#endif
- )
- return 1;
-#endif
- }
-
- switch (code)
- {
- case REG:
-
-#if defined(POINTERS_EXTEND_UNSIGNED) && !defined(HAVE_ptr_extend)
- /* If pointers extend signed and this is a pointer in Pmode, say that
- all the bits above ptr_mode are known to be sign bit copies. */
- if (! POINTERS_EXTEND_UNSIGNED && GET_MODE (x) == Pmode && mode == Pmode
- && REG_POINTER (x))
- return GET_MODE_BITSIZE (Pmode) - GET_MODE_BITSIZE (ptr_mode) + 1;
-#endif
-
- if (reg_last_set_value[REGNO (x)] != 0
- && reg_last_set_mode[REGNO (x)] == mode
- && (reg_last_set_label[REGNO (x)] == label_tick
- || (REGNO (x) >= FIRST_PSEUDO_REGISTER
- && REG_N_SETS (REGNO (x)) == 1
- && ! REGNO_REG_SET_P (ENTRY_BLOCK_PTR->next_bb->global_live_at_start,
- REGNO (x))))
- && INSN_CUID (reg_last_set[REGNO (x)]) < subst_low_cuid)
- return reg_last_set_sign_bit_copies[REGNO (x)];
-
- tem = get_last_value (x);
- if (tem != 0)
- return num_sign_bit_copies_with_known (tem, mode);
-
- if (nonzero_sign_valid && reg_sign_bit_copies[REGNO (x)] != 0
- && GET_MODE_BITSIZE (GET_MODE (x)) == bitwidth)
- return reg_sign_bit_copies[REGNO (x)];
- break;
-
- case MEM:
-#ifdef LOAD_EXTEND_OP
- /* Some RISC machines sign-extend all loads of smaller than a word. */
- if (LOAD_EXTEND_OP (GET_MODE (x)) == SIGN_EXTEND)
- return MAX (1, ((int) bitwidth
- - (int) GET_MODE_BITSIZE (GET_MODE (x)) + 1));
-#endif
- break;
-
- case CONST_INT:
- /* If the constant is negative, take its 1's complement and remask.
- Then see how many zero bits we have. */
- nonzero = INTVAL (x) & GET_MODE_MASK (mode);
- if (bitwidth <= HOST_BITS_PER_WIDE_INT
- && (nonzero & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0)
- nonzero = (~nonzero) & GET_MODE_MASK (mode);
-
- return (nonzero == 0 ? bitwidth : bitwidth - floor_log2 (nonzero) - 1);
-
- case SUBREG:
- /* If this is a SUBREG for a promoted object that is sign-extended
- and we are looking at it in a wider mode, we know that at least the
- high-order bits are known to be sign bit copies. */
-
- if (SUBREG_PROMOTED_VAR_P (x) && ! SUBREG_PROMOTED_UNSIGNED_P (x))
- {
- num0 = num_sign_bit_copies_with_known (SUBREG_REG (x), mode);
- return MAX ((int) bitwidth
- - (int) GET_MODE_BITSIZE (GET_MODE (x)) + 1,
- num0);
- }
-
- /* For a smaller object, just ignore the high bits. */
- if (bitwidth <= GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))))
- {
- num0 = num_sign_bit_copies_with_known (SUBREG_REG (x), VOIDmode);
- return MAX (1, (num0
- - (int) (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x)))
- - bitwidth)));
- }
-
-#ifdef WORD_REGISTER_OPERATIONS
-#ifdef LOAD_EXTEND_OP
- /* For paradoxical SUBREGs on machines where all register operations
- affect the entire register, just look inside. Note that we are
- passing MODE to the recursive call, so the number of sign bit copies
- will remain relative to that mode, not the inner mode. */
-
- /* This works only if loads sign extend. Otherwise, if we get a
- reload for the inner part, it may be loaded from the stack, and
- then we lose all sign bit copies that existed before the store
- to the stack. */
-
- if ((GET_MODE_SIZE (GET_MODE (x))
- > GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
- && LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (x))) == SIGN_EXTEND
- && GET_CODE (SUBREG_REG (x)) == MEM)
- return num_sign_bit_copies_with_known (SUBREG_REG (x), mode);
-#endif
-#endif
- break;
-
- case SIGN_EXTRACT:
- if (GET_CODE (XEXP (x, 1)) == CONST_INT)
- return MAX (1, (int) bitwidth - INTVAL (XEXP (x, 1)));
- break;
-
- case SIGN_EXTEND:
- return (bitwidth - GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))
- + num_sign_bit_copies_with_known (XEXP (x, 0), VOIDmode));
-
- case TRUNCATE:
- /* For a smaller object, just ignore the high bits. */
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), VOIDmode);
- return MAX (1, (num0 - (int) (GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))
- - bitwidth)));
-
- case NOT:
- return num_sign_bit_copies_with_known (XEXP (x, 0), mode);
-
- case ROTATE: case ROTATERT:
- /* If we are rotating left by a number of bits less than the number
- of sign bit copies, we can just subtract that amount from the
- number. */
- if (GET_CODE (XEXP (x, 1)) == CONST_INT
- && INTVAL (XEXP (x, 1)) >= 0
- && INTVAL (XEXP (x, 1)) < (int) bitwidth)
- {
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- return MAX (1, num0 - (code == ROTATE ? INTVAL (XEXP (x, 1))
- : (int) bitwidth - INTVAL (XEXP (x, 1))));
- }
- break;
-
- case NEG:
- /* In general, this subtracts one sign bit copy. But if the value
- is known to be positive, the number of sign bit copies is the
- same as that of the input. Finally, if the input has just one bit
- that might be nonzero, all the bits are copies of the sign bit. */
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- if (bitwidth > HOST_BITS_PER_WIDE_INT)
- return num0 > 1 ? num0 - 1 : 1;
-
- nonzero = nonzero_bits (XEXP (x, 0), mode);
- if (nonzero == 1)
- return bitwidth;
-
- if (num0 > 1
- && (((HOST_WIDE_INT) 1 << (bitwidth - 1)) & nonzero))
- num0--;
-
- return num0;
-
- case IOR: case AND: case XOR:
- case SMIN: case SMAX: case UMIN: case UMAX:
- /* Logical operations will preserve the number of sign-bit copies.
- MIN and MAX operations always return one of the operands. */
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- num1 = num_sign_bit_copies_with_known (XEXP (x, 1), mode);
- return MIN (num0, num1);
-
- case PLUS: case MINUS:
- /* For addition and subtraction, we can have a 1-bit carry. However,
- if we are subtracting 1 from a positive number, there will not
- be such a carry. Furthermore, if the positive number is known to
- be 0 or 1, we know the result is either -1 or 0. */
-
- if (code == PLUS && XEXP (x, 1) == constm1_rtx
- && bitwidth <= HOST_BITS_PER_WIDE_INT)
- {
- nonzero = nonzero_bits (XEXP (x, 0), mode);
- if ((((HOST_WIDE_INT) 1 << (bitwidth - 1)) & nonzero) == 0)
- return (nonzero == 1 || nonzero == 0 ? bitwidth
- : bitwidth - floor_log2 (nonzero) - 1);
- }
-
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- num1 = num_sign_bit_copies_with_known (XEXP (x, 1), mode);
- result = MAX (1, MIN (num0, num1) - 1);
-
-#ifdef POINTERS_EXTEND_UNSIGNED
- /* If pointers extend signed and this is an addition or subtraction
- to a pointer in Pmode, all the bits above ptr_mode are known to be
- sign bit copies. */
- if (! POINTERS_EXTEND_UNSIGNED && GET_MODE (x) == Pmode
- && (code == PLUS || code == MINUS)
- && GET_CODE (XEXP (x, 0)) == REG && REG_POINTER (XEXP (x, 0)))
- result = MAX ((int) (GET_MODE_BITSIZE (Pmode)
- - GET_MODE_BITSIZE (ptr_mode) + 1),
- result);
-#endif
- return result;
-
- case MULT:
- /* The number of bits of the product is the sum of the number of
- bits of both terms. However, unless one of the terms if known
- to be positive, we must allow for an additional bit since negating
- a negative number can remove one sign bit copy. */
-
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- num1 = num_sign_bit_copies_with_known (XEXP (x, 1), mode);
-
- result = bitwidth - (bitwidth - num0) - (bitwidth - num1);
- if (result > 0
- && (bitwidth > HOST_BITS_PER_WIDE_INT
- || (((nonzero_bits (XEXP (x, 0), mode)
- & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0)
- && ((nonzero_bits (XEXP (x, 1), mode)
- & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0))))
- result--;
-
- return MAX (1, result);
-
- case UDIV:
- /* The result must be <= the first operand. If the first operand
- has the high bit set, we know nothing about the number of sign
- bit copies. */
- if (bitwidth > HOST_BITS_PER_WIDE_INT)
- return 1;
- else if ((nonzero_bits (XEXP (x, 0), mode)
- & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0)
- return 1;
- else
- return num_sign_bit_copies_with_known (XEXP (x, 0), mode);
-
- case UMOD:
- /* The result must be <= the second operand. */
- return num_sign_bit_copies_with_known (XEXP (x, 1), mode);
-
- case DIV:
- /* Similar to unsigned division, except that we have to worry about
- the case where the divisor is negative, in which case we have
- to add 1. */
- result = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- if (result > 1
- && (bitwidth > HOST_BITS_PER_WIDE_INT
- || (nonzero_bits (XEXP (x, 1), mode)
- & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0))
- result--;
-
- return result;
-
- case MOD:
- result = num_sign_bit_copies_with_known (XEXP (x, 1), mode);
- if (result > 1
- && (bitwidth > HOST_BITS_PER_WIDE_INT
- || (nonzero_bits (XEXP (x, 1), mode)
- & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0))
- result--;
-
- return result;
-
- case ASHIFTRT:
- /* Shifts by a constant add to the number of bits equal to the
- sign bit. */
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- if (GET_CODE (XEXP (x, 1)) == CONST_INT
- && INTVAL (XEXP (x, 1)) > 0)
- num0 = MIN ((int) bitwidth, num0 + INTVAL (XEXP (x, 1)));
-
- return num0;
-
- case ASHIFT:
- /* Left shifts destroy copies. */
- if (GET_CODE (XEXP (x, 1)) != CONST_INT
- || INTVAL (XEXP (x, 1)) < 0
- || INTVAL (XEXP (x, 1)) >= (int) bitwidth)
- return 1;
-
- num0 = num_sign_bit_copies_with_known (XEXP (x, 0), mode);
- return MAX (1, num0 - INTVAL (XEXP (x, 1)));
-
- case IF_THEN_ELSE:
- num0 = num_sign_bit_copies_with_known (XEXP (x, 1), mode);
- num1 = num_sign_bit_copies_with_known (XEXP (x, 2), mode);
- return MIN (num0, num1);
-
- case EQ: case NE: case GE: case GT: case LE: case LT:
- case UNEQ: case LTGT: case UNGE: case UNGT: case UNLE: case UNLT:
- case GEU: case GTU: case LEU: case LTU:
- case UNORDERED: case ORDERED:
- /* If the constant is negative, take its 1's complement and remask.
- Then see how many zero bits we have. */
- nonzero = STORE_FLAG_VALUE;
- if (bitwidth <= HOST_BITS_PER_WIDE_INT
- && (nonzero & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0)
- nonzero = (~nonzero) & GET_MODE_MASK (mode);
-
- return (nonzero == 0 ? bitwidth : bitwidth - floor_log2 (nonzero) - 1);
- break;
-
- default:
- break;
- }
-
- /* If we haven't been able to figure it out by one of the above rules,
- see if some of the high-order bits are known to be zero. If so,
- count those bits and return one less than that amount. If we can't
- safely compute the mask for this mode, always return BITWIDTH. */
-
- if (bitwidth > HOST_BITS_PER_WIDE_INT)
- return 1;
-
- nonzero = nonzero_bits (x, mode);
- return (nonzero & ((HOST_WIDE_INT) 1 << (bitwidth - 1))
- ? 1 : bitwidth - floor_log2 (nonzero) - 1);
-}
-\f
-/* Return the number of "extended" bits there are in X, when interpreted
- as a quantity in MODE whose signedness is indicated by UNSIGNEDP. For
- unsigned quantities, this is the number of high-order zero bits.
- For signed quantities, this is the number of copies of the sign bit
- minus 1. In both case, this function returns the number of "spare"
- bits. For example, if two quantities for which this function returns
- at least 1 are added, the addition is known not to overflow.
-
- This function will always return 0 unless called during combine, which
- implies that it must be called from a define_split. */