On Mar 26, 2012, at 1:03 PM, Richard Sandiford wrote:
> I think:
>
> ...copies of the top bit. Note however that values are neither inherently
> signed nor inherently unsigned; where necessary, signedness is determined
> by the rtl operation instead.
Sounds good to me, changed.
> Same idea here.
Fixed.
>> +/* Return an rtx for the sum of X and the integer C, given that X has
>> + mode MODE. This routine should be used instead of plus_constant
>> + when they want to ensure that addition happens in a particular
>> + mode, which is necessary when x can be a VOIDmode CONST_INT or
>
> Sorry, just noticed, should be "...when X can be..."
Fixed.
Richard has ok all his bits, now down to you for final ok.
Ok?
* doc/rtl.texi (const_double): Document as sign-extending.
* expmed.c (expand_mult): Ensure we don't use shift
incorrectly.
* emit-rtl.c (immed_double_int_const): Refine to state the
value is signed.
* simplify-rtx.c (mode_signbit_p): Add a fixme for wider than
CONST_DOUBLE integers.
(simplify_const_unary_operation, UNSIGNED_FLOAT): Ensure no
negative values are converted. Fix conversions bigger than
HOST_BITS_PER_WIDE_INT.
(simplify_binary_operation_1): Ensure we don't use shift
incorrectly.
(simplify_immed_subreg): Sign-extend CONST_DOUBLEs.
* explow.c (plus_constant_mode): Add.
(plus_constant): Implement with plus_constant_mode.
* rtl.h (plus_constant_mode): Add.
Index: doc/rtl.texi
===================================================================
--- doc/rtl.texi (revision 185706)
+++ doc/rtl.texi (working copy)
@@ -1479,8 +1479,19 @@ This type of expression represents the i
is customarily accessed with the macro @code{INTVAL} as in
@code{INTVAL (@var{exp})}, which is equivalent to @code{XWINT (@var{exp}, 0)}.
-Constants generated for modes with fewer bits than @code{HOST_WIDE_INT}
-must be sign extended to full width (e.g., with @code{gen_int_mode}).
+Constants generated for modes with fewer bits than in
+@code{HOST_WIDE_INT} must be sign extended to full width (e.g., with
+@code{gen_int_mode}). For constants for modes with more bits than in
+@code{HOST_WIDE_INT} the implied high order bits of that constant are
+copies of the top bit. Note however that values are neither
+inherently signed nor inherently unsigned; where necessary, signedness
+is determined by the rtl operation instead.
+
+
+, however values are neither signed nor unsigned.
+All operations defined on such constants define the signededness.
+
+
@findex const0_rtx
@findex const1_rtx
@@ -1510,7 +1521,13 @@ Represents either a floating-point const
integer constant too large to fit into @code{HOST_BITS_PER_WIDE_INT}
bits but small enough to fit within twice that number of bits (GCC
does not provide a mechanism to represent even larger constants). In
-the latter case, @var{m} will be @code{VOIDmode}.
+the latter case, @var{m} will be @code{VOIDmode}. For integral values
+constants for modes with more bits than twice the number in
+@code{HOST_WIDE_INT} the implied high order bits of that constant are
+copies of the top bit of @code{CONST_DOUBLE_HIGH}. Note however that
+integral values are neither inherently signed nor inherently unsigned;
+where necessary, signedness is determined by the rtl operation
+instead.
@findex CONST_DOUBLE_LOW
If @var{m} is @code{VOIDmode}, the bits of the value are stored in
Index: expmed.c
===================================================================
--- expmed.c (revision 185706)
+++ expmed.c (working copy)
@@ -3135,8 +3135,10 @@ expand_mult (enum machine_mode mode, rtx
{
int shift = floor_log2 (CONST_DOUBLE_HIGH (op1))
+ HOST_BITS_PER_WIDE_INT;
- return expand_shift (LSHIFT_EXPR, mode, op0,
- shift, target, unsignedp);
+ if (shift < 2 * HOST_BITS_PER_WIDE_INT - 1
+ || GET_MODE_BITSIZE (mode) <= 2 * HOST_BITS_PER_WIDE_INT)
+ return expand_shift (LSHIFT_EXPR, mode, op0,
+ shift, target, unsignedp);
}
}
Index: emit-rtl.c
===================================================================
--- emit-rtl.c (revision 185706)
+++ emit-rtl.c (working copy)
@@ -517,8 +517,11 @@ immed_double_int_const (double_int i, en
/* Return a CONST_DOUBLE or CONST_INT for a value specified as a pair
of ints: I0 is the low-order word and I1 is the high-order word.
- Do not use this routine for non-integer modes; convert to
- REAL_VALUE_TYPE and use CONST_DOUBLE_FROM_REAL_VALUE. */
+ For values that are larger than 2*HOST_BITS_PER_WIDE_INT, the
+ implied upper bits are copies of the high bit of i1. The value
+ itself is neither signed nor unsigned. Do not use this routine for
+ non-integer modes; convert to REAL_VALUE_TYPE and use
+ CONST_DOUBLE_FROM_REAL_VALUE. */
rtx
immed_double_const (HOST_WIDE_INT i0, HOST_WIDE_INT i1, enum machine_mode mode)
@@ -531,10 +534,9 @@ immed_double_const (HOST_WIDE_INT i0, HO
1) If GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT, then we use
gen_int_mode.
- 2) GET_MODE_BITSIZE (mode) == 2 * HOST_BITS_PER_WIDE_INT, but the value of
- the integer fits into HOST_WIDE_INT anyway (i.e., i1 consists only
- from copies of the sign bit, and sign of i0 and i1 are the same), then
- we return a CONST_INT for i0.
+ 2) If the value of the integer fits into HOST_WIDE_INT anyway
+ (i.e., i1 consists only from copies of the sign bit, and sign
+ of i0 and i1 are the same), then we return a CONST_INT for i0.
3) Otherwise, we create a CONST_DOUBLE for i0 and i1. */
if (mode != VOIDmode)
{
@@ -546,8 +548,6 @@ immed_double_const (HOST_WIDE_INT i0, HO
if (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
return gen_int_mode (i0, mode);
-
- gcc_assert (GET_MODE_BITSIZE (mode) == 2 * HOST_BITS_PER_WIDE_INT);
}
/* If this integer fits in one word, return a CONST_INT. */
Index: simplify-rtx.c
===================================================================
--- simplify-rtx.c (revision 185706)
+++ simplify-rtx.c (working copy)
@@ -97,6 +97,7 @@ mode_signbit_p (enum machine_mode mode,
width -= HOST_BITS_PER_WIDE_INT;
}
else
+ /* FIXME: We don't yet have a representation for wider modes. */
return false;
if (width < HOST_BITS_PER_WIDE_INT)
@@ -1355,16 +1356,11 @@ simplify_const_unary_operation (enum rtx
else
lv = CONST_DOUBLE_LOW (op), hv = CONST_DOUBLE_HIGH (op);
- if (op_mode == VOIDmode)
- {
- /* We don't know how to interpret negative-looking numbers in
- this case, so don't try to fold those. */
- if (hv < 0)
- return 0;
- }
- else if (GET_MODE_PRECISION (op_mode) >= HOST_BITS_PER_WIDE_INT * 2)
- ;
- else
+ if (op_mode == VOIDmode
+ || GET_MODE_PRECISION (op_mode) > 2 * HOST_BITS_PER_WIDE_INT)
+ /* We should never get a negative number. */
+ gcc_assert (hv >= 0);
+ else if (GET_MODE_PRECISION (op_mode) <= HOST_BITS_PER_WIDE_INT)
hv = 0, lv &= GET_MODE_MASK (op_mode);
REAL_VALUE_FROM_UNSIGNED_INT (d, lv, hv, mode);
@@ -1718,7 +1714,7 @@ simplify_const_unary_operation (enum rtx
else if (GET_CODE (op) == CONST_DOUBLE
&& SCALAR_FLOAT_MODE_P (GET_MODE (op))
&& GET_MODE_CLASS (mode) == MODE_INT
- && width <= 2*HOST_BITS_PER_WIDE_INT && width > 0)
+ && width <= 2 * HOST_BITS_PER_WIDE_INT && width > 0)
{
/* Although the overflow semantics of RTL's FIX and UNSIGNED_FIX
operators are intentionally left unspecified (to ease implementation
@@ -1783,7 +1779,7 @@ simplify_const_unary_operation (enum rtx
return const0_rtx;
/* Test against the unsigned upper bound. */
- if (width == 2*HOST_BITS_PER_WIDE_INT)
+ if (width == 2 * HOST_BITS_PER_WIDE_INT)
{
th = -1;
tl = -1;
@@ -2380,7 +2376,9 @@ simplify_binary_operation_1 (enum rtx_co
|| GET_MODE_CLASS (GET_MODE (trueop1)) == MODE_INT)
&& GET_MODE (op0) == mode
&& CONST_DOUBLE_LOW (trueop1) == 0
- && (val = exact_log2 (CONST_DOUBLE_HIGH (trueop1))) >= 0)
+ && (val = exact_log2 (CONST_DOUBLE_HIGH (trueop1))) >= 0
+ && (val < 2 * HOST_BITS_PER_WIDE_INT - 1
+ || GET_MODE_BITSIZE (mode) <= 2 * HOST_BITS_PER_WIDE_INT))
return simplify_gen_binary (ASHIFT, mode, op0,
GEN_INT (val + HOST_BITS_PER_WIDE_INT));
@@ -5189,6 +5187,7 @@ simplify_immed_subreg (enum machine_mode
case CONST_DOUBLE:
if (GET_MODE (el) == VOIDmode)
{
+ unsigned char extend = 0;
/* If this triggers, someone should have generated a
CONST_INT instead. */
gcc_assert (elem_bitsize > HOST_BITS_PER_WIDE_INT);
@@ -5201,10 +5200,11 @@ simplify_immed_subreg (enum machine_mode
= CONST_DOUBLE_HIGH (el) >> (i - HOST_BITS_PER_WIDE_INT);
i += value_bit;
}
- /* It shouldn't matter what's done here, so fill it with
- zero. */
+
+ if (CONST_DOUBLE_HIGH (el) >> (HOST_BITS_PER_WIDE_INT - 1))
+ extend = -1;
for (; i < elem_bitsize; i += value_bit)
- *vp++ = 0;
+ *vp++ = extend;
}
else
{
Index: explow.c
===================================================================
--- explow.c (revision 185706)
+++ explow.c (working copy)
@@ -74,14 +74,20 @@ trunc_int_for_mode (HOST_WIDE_INT c, enu
return c;
}
-/* Return an rtx for the sum of X and the integer C. */
+/* Return an rtx for the sum of X and the integer C, given that X has
+ mode MODE. This routine should be used instead of plus_constant
+ when they want to ensure that addition happens in a particular
+ mode, which is necessary when X can be a VOIDmode CONST_INT or
+ CONST_DOUBLE and the width of the constant is different from the
+ width of the expression. */
+/* TODO: All callers of plus_constant should migrate to this routine,
+ and once they do, we can assert that mode is not VOIDmode. */
rtx
-plus_constant (rtx x, HOST_WIDE_INT c)
+plus_constant_mode (enum machine_mode mode, rtx x, HOST_WIDE_INT c)
{
RTX_CODE code;
rtx y;
- enum machine_mode mode;
rtx tem;
int all_constant = 0;
@@ -91,12 +97,26 @@ plus_constant (rtx x, HOST_WIDE_INT c)
restart:
code = GET_CODE (x);
- mode = GET_MODE (x);
y = x;
switch (code)
{
case CONST_INT:
+ if (GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT)
+ {
+ unsigned HOST_WIDE_INT l1 = INTVAL (x);
+ HOST_WIDE_INT h1 = (l1 >> (HOST_BITS_PER_WIDE_INT - 1)) ? -1 : 0;
+ unsigned HOST_WIDE_INT l2 = c;
+ HOST_WIDE_INT h2 = c < 0 ? -1 : 0;
+ unsigned HOST_WIDE_INT lv;
+ HOST_WIDE_INT hv;
+
+ if (add_double_with_sign (l1, h1, l2, h2, &lv, &hv, false))
+ gcc_unreachable ();
+
+ return immed_double_const (lv, hv, VOIDmode);
+ }
+
return GEN_INT (INTVAL (x) + c);
case CONST_DOUBLE:
@@ -104,11 +124,14 @@ plus_constant (rtx x, HOST_WIDE_INT c)
unsigned HOST_WIDE_INT l1 = CONST_DOUBLE_LOW (x);
HOST_WIDE_INT h1 = CONST_DOUBLE_HIGH (x);
unsigned HOST_WIDE_INT l2 = c;
- HOST_WIDE_INT h2 = c < 0 ? ~0 : 0;
+ HOST_WIDE_INT h2 = c < 0 ? -1 : 0;
unsigned HOST_WIDE_INT lv;
HOST_WIDE_INT hv;
- add_double (l1, h1, l2, h2, &lv, &hv);
+ if (add_double_with_sign (l1, h1, l2, h2, &lv, &hv, false))
+ /* Sorry, we have no way to represent overflows this wide.
+ To fix, add constant support wider than CONST_DOUBLE. */
+ gcc_assert (GET_MODE_BITSIZE (mode) <= 2 * HOST_BITS_PER_WIDE_INT);
return immed_double_const (lv, hv, VOIDmode);
}
@@ -120,10 +143,8 @@ plus_constant (rtx x, HOST_WIDE_INT c)
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));
+ tem = plus_constant_mode (mode, get_pool_constant (XEXP (x, 0)), c);
+ tem = force_const_mem (GET_MODE (x), tem);
if (memory_address_p (GET_MODE (tem), XEXP (tem, 0)))
return tem;
}
@@ -142,31 +163,17 @@ plus_constant (rtx x, HOST_WIDE_INT c)
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.
-
- Restart or use a recursive call in case the remaining operand is
- something that we handle specially, such as a SYMBOL_REF.
+ /* 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 or a constant term that is not an
+ explicit integer, we combine or group them together anyway.
We may not immediately return from the recursive call here, lest
all_constant gets lost. */
- if (CONST_INT_P (XEXP (x, 1)))
+ if (CONSTANT_P (XEXP (x, 1)))
{
- c += INTVAL (XEXP (x, 1));
-
- if (GET_MODE (x) != VOIDmode)
- c = trunc_int_for_mode (c, GET_MODE (x));
-
- x = XEXP (x, 0);
- goto restart;
- }
- else if (CONSTANT_P (XEXP (x, 1)))
- {
- x = gen_rtx_PLUS (mode, XEXP (x, 0), plus_constant (XEXP (x, 1), c));
+ x = gen_rtx_PLUS (mode, XEXP (x, 0), plus_constant_mode (mode, XEXP
(x, 1), c));
c = 0;
}
else if (find_constant_term_loc (&y))
@@ -176,7 +183,7 @@ plus_constant (rtx x, HOST_WIDE_INT c)
rtx copy = copy_rtx (x);
rtx *const_loc = find_constant_term_loc (©);
- *const_loc = plus_constant (*const_loc, c);
+ *const_loc = plus_constant_mode (mode, *const_loc, c);
x = copy;
c = 0;
}
@@ -196,6 +203,14 @@ plus_constant (rtx x, HOST_WIDE_INT c)
else
return x;
}
+
+/* Return an rtx for the sum of X and the integer C. */
+
+rtx
+plus_constant (rtx x, HOST_WIDE_INT c)
+{
+ return plus_constant_mode (GET_MODE (x), 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.
Index: rtl.h
===================================================================
--- rtl.h (revision 185706)
+++ rtl.h (working copy)
@@ -1644,6 +1644,7 @@ extern int ceil_log2 (unsigned HOST_WIDE
/* In explow.c */
extern HOST_WIDE_INT trunc_int_for_mode (HOST_WIDE_INT, enum
machine_mode);
extern rtx plus_constant (rtx, HOST_WIDE_INT);
+extern rtx plus_constant_mode (enum machine_mode, rtx, HOST_WIDE_INT);
/* In rtl.c */
extern rtx rtx_alloc_stat (RTX_CODE MEM_STAT_DECL);
