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re PR tree-optimization/46728 (GCC does not generate fmadd for pow (x, 0.75)+y on powerpc)

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2011-06-06  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	PR tree-optimization/46728
	* builtins.c (powi_table): Remove.
	(powi_lookup_cost): Remove.
	(powi_cost): Remove.
	(expand_powi_1): Remove.
	(expand_powi): Remove.
	(expand_builtin_pow_root): Remove.
	(expand_builtin_pow): Remove.
	(expand_builtin_powi): Eliminate handling of constant exponent.
	(expand_builtin): Use expand_builtin_mathfn_2 for BUILT_IN_POW.

From-SVN: r174701
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Bill Schmidt 2011-06-06 14:27:41 +00:00 committed by William Schmidt
parent 3598cabdae
commit 3906ea1b34
2 changed files with 14 additions and 472 deletions
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13
gcc/ChangeLog
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@ -1,3 +1,16 @@
2011-06-06 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
PR tree-optimization/46728
* builtins.c (powi_table): Remove.
(powi_lookup_cost): Remove.
(powi_cost): Remove.
(expand_powi_1): Remove.
(expand_powi): Remove.
(expand_builtin_pow_root): Remove.
(expand_builtin_pow): Remove.
(expand_builtin_powi): Eliminate handling of constant exponent.
(expand_builtin): Use expand_builtin_mathfn_2 for BUILT_IN_POW.
2011-06-06 Alexandre Oliva <aoliva@redhat.com>
* cprop.c (local_cprop_pass): Don't set changed for debug insns.

473
gcc/builtins.c
View File

@ -2823,451 +2823,6 @@ expand_builtin_int_roundingfn_2 (tree exp, rtx target)
return target;
}
/* To evaluate powi(x,n), the floating point value x raised to the
constant integer exponent n, we use a hybrid algorithm that
combines the "window method" with look-up tables. For an
introduction to exponentiation algorithms and "addition chains",
see section 4.6.3, "Evaluation of Powers" of Donald E. Knuth,
"Seminumerical Algorithms", Vol. 2, "The Art of Computer Programming",
3rd Edition, 1998, and Daniel M. Gordon, "A Survey of Fast Exponentiation
Methods", Journal of Algorithms, Vol. 27, pp. 129-146, 1998. */
/* Provide a default value for POWI_MAX_MULTS, the maximum number of
multiplications to inline before calling the system library's pow
function. powi(x,n) requires at worst 2*bits(n)-2 multiplications,
so this default never requires calling pow, powf or powl. */
#ifndef POWI_MAX_MULTS
#define POWI_MAX_MULTS (2*HOST_BITS_PER_WIDE_INT-2)
#endif
/* The size of the "optimal power tree" lookup table. All
exponents less than this value are simply looked up in the
powi_table below. This threshold is also used to size the
cache of pseudo registers that hold intermediate results. */
#define POWI_TABLE_SIZE 256
/* The size, in bits of the window, used in the "window method"
exponentiation algorithm. This is equivalent to a radix of
(1<<POWI_WINDOW_SIZE) in the corresponding "m-ary method". */
#define POWI_WINDOW_SIZE 3
/* The following table is an efficient representation of an
"optimal power tree". For each value, i, the corresponding
value, j, in the table states than an optimal evaluation
sequence for calculating pow(x,i) can be found by evaluating
pow(x,j)*pow(x,i-j). An optimal power tree for the first
100 integers is given in Knuth's "Seminumerical algorithms". */
static const unsigned char powi_table[POWI_TABLE_SIZE] =
{
0, 1, 1, 2, 2, 3, 3, 4, /* 0 - 7 */
4, 6, 5, 6, 6, 10, 7, 9, /* 8 - 15 */
8, 16, 9, 16, 10, 12, 11, 13, /* 16 - 23 */
12, 17, 13, 18, 14, 24, 15, 26, /* 24 - 31 */
16, 17, 17, 19, 18, 33, 19, 26, /* 32 - 39 */
20, 25, 21, 40, 22, 27, 23, 44, /* 40 - 47 */
24, 32, 25, 34, 26, 29, 27, 44, /* 48 - 55 */
28, 31, 29, 34, 30, 60, 31, 36, /* 56 - 63 */
32, 64, 33, 34, 34, 46, 35, 37, /* 64 - 71 */
36, 65, 37, 50, 38, 48, 39, 69, /* 72 - 79 */
40, 49, 41, 43, 42, 51, 43, 58, /* 80 - 87 */
44, 64, 45, 47, 46, 59, 47, 76, /* 88 - 95 */
48, 65, 49, 66, 50, 67, 51, 66, /* 96 - 103 */
52, 70, 53, 74, 54, 104, 55, 74, /* 104 - 111 */
56, 64, 57, 69, 58, 78, 59, 68, /* 112 - 119 */
60, 61, 61, 80, 62, 75, 63, 68, /* 120 - 127 */
64, 65, 65, 128, 66, 129, 67, 90, /* 128 - 135 */
68, 73, 69, 131, 70, 94, 71, 88, /* 136 - 143 */
72, 128, 73, 98, 74, 132, 75, 121, /* 144 - 151 */
76, 102, 77, 124, 78, 132, 79, 106, /* 152 - 159 */
80, 97, 81, 160, 82, 99, 83, 134, /* 160 - 167 */
84, 86, 85, 95, 86, 160, 87, 100, /* 168 - 175 */
88, 113, 89, 98, 90, 107, 91, 122, /* 176 - 183 */
92, 111, 93, 102, 94, 126, 95, 150, /* 184 - 191 */
96, 128, 97, 130, 98, 133, 99, 195, /* 192 - 199 */
100, 128, 101, 123, 102, 164, 103, 138, /* 200 - 207 */
104, 145, 105, 146, 106, 109, 107, 149, /* 208 - 215 */
108, 200, 109, 146, 110, 170, 111, 157, /* 216 - 223 */
112, 128, 113, 130, 114, 182, 115, 132, /* 224 - 231 */
116, 200, 117, 132, 118, 158, 119, 206, /* 232 - 239 */
120, 240, 121, 162, 122, 147, 123, 152, /* 240 - 247 */
124, 166, 125, 214, 126, 138, 127, 153, /* 248 - 255 */
};
/* Return the number of multiplications required to calculate
powi(x,n) where n is less than POWI_TABLE_SIZE. This is a
subroutine of powi_cost. CACHE is an array indicating
which exponents have already been calculated. */
static int
powi_lookup_cost (unsigned HOST_WIDE_INT n, bool *cache)
{
/* If we've already calculated this exponent, then this evaluation
doesn't require any additional multiplications. */
if (cache[n])
return 0;
cache[n] = true;
return powi_lookup_cost (n - powi_table[n], cache)
+ powi_lookup_cost (powi_table[n], cache) + 1;
}
/* Return the number of multiplications required to calculate
powi(x,n) for an arbitrary x, given the exponent N. This
function needs to be kept in sync with expand_powi below. */
static int
powi_cost (HOST_WIDE_INT n)
{
bool cache[POWI_TABLE_SIZE];
unsigned HOST_WIDE_INT digit;
unsigned HOST_WIDE_INT val;
int result;
if (n == 0)
return 0;
/* Ignore the reciprocal when calculating the cost. */
val = (n < 0) ? -n : n;
/* Initialize the exponent cache. */
memset (cache, 0, POWI_TABLE_SIZE * sizeof (bool));
cache[1] = true;
result = 0;
while (val >= POWI_TABLE_SIZE)
{
if (val & 1)
{
digit = val & ((1 << POWI_WINDOW_SIZE) - 1);
result += powi_lookup_cost (digit, cache)
+ POWI_WINDOW_SIZE + 1;
val >>= POWI_WINDOW_SIZE;
}
else
{
val >>= 1;
result++;
}
}
return result + powi_lookup_cost (val, cache);
}
/* Recursive subroutine of expand_powi. This function takes the array,
CACHE, of already calculated exponents and an exponent N and returns
an RTX that corresponds to CACHE[1]**N, as calculated in mode MODE. */
static rtx
expand_powi_1 (enum machine_mode mode, unsigned HOST_WIDE_INT n, rtx *cache)
{
unsigned HOST_WIDE_INT digit;
rtx target, result;
rtx op0, op1;
if (n < POWI_TABLE_SIZE)
{
if (cache[n])
return cache[n];
target = gen_reg_rtx (mode);
cache[n] = target;
op0 = expand_powi_1 (mode, n - powi_table[n], cache);
op1 = expand_powi_1 (mode, powi_table[n], cache);
}
else if (n & 1)
{
target = gen_reg_rtx (mode);
digit = n & ((1 << POWI_WINDOW_SIZE) - 1);
op0 = expand_powi_1 (mode, n - digit, cache);
op1 = expand_powi_1 (mode, digit, cache);
}
else
{
target = gen_reg_rtx (mode);
op0 = expand_powi_1 (mode, n >> 1, cache);
op1 = op0;
}
result = expand_mult (mode, op0, op1, target, 0);
if (result != target)
emit_move_insn (target, result);
return target;
}
/* Expand the RTL to evaluate powi(x,n) in mode MODE. X is the
floating point operand in mode MODE, and N is the exponent. This
function needs to be kept in sync with powi_cost above. */
static rtx
expand_powi (rtx x, enum machine_mode mode, HOST_WIDE_INT n)
{
rtx cache[POWI_TABLE_SIZE];
rtx result;
if (n == 0)
return CONST1_RTX (mode);
memset (cache, 0, sizeof (cache));
cache[1] = x;
result = expand_powi_1 (mode, (n < 0) ? -n : n, cache);
/* If the original exponent was negative, reciprocate the result. */
if (n < 0)
result = expand_binop (mode, sdiv_optab, CONST1_RTX (mode),
result, NULL_RTX, 0, OPTAB_LIB_WIDEN);
return result;
}
/* Fold a builtin function call to pow, powf, or powl into a series of sqrts or
cbrts. Return NULL_RTX if no simplification can be made or expand the tree
if we can simplify it. */
static rtx
expand_builtin_pow_root (location_t loc, tree arg0, tree arg1, tree type,
rtx subtarget)
{
if (TREE_CODE (arg1) == REAL_CST
&& !TREE_OVERFLOW (arg1)
&& flag_unsafe_math_optimizations)
{
enum machine_mode mode = TYPE_MODE (type);
tree sqrtfn = mathfn_built_in (type, BUILT_IN_SQRT);
tree cbrtfn = mathfn_built_in (type, BUILT_IN_CBRT);
REAL_VALUE_TYPE c = TREE_REAL_CST (arg1);
tree op = NULL_TREE;
if (sqrtfn)
{
/* Optimize pow (x, 0.5) into sqrt. */
if (REAL_VALUES_EQUAL (c, dconsthalf))
op = build_call_nofold_loc (loc, sqrtfn, 1, arg0);
/* Don't do this optimization if we don't have a sqrt insn. */
else if (optab_handler (sqrt_optab, mode) != CODE_FOR_nothing)
{
REAL_VALUE_TYPE dconst1_4 = dconst1;
REAL_VALUE_TYPE dconst3_4;
SET_REAL_EXP (&dconst1_4, REAL_EXP (&dconst1_4) - 2);
real_from_integer (&dconst3_4, VOIDmode, 3, 0, 0);
SET_REAL_EXP (&dconst3_4, REAL_EXP (&dconst3_4) - 2);
/* Optimize pow (x, 0.25) into sqrt (sqrt (x)). Assume on most
machines that a builtin sqrt instruction is smaller than a
call to pow with 0.25, so do this optimization even if
-Os. */
if (REAL_VALUES_EQUAL (c, dconst1_4))
{
op = build_call_nofold_loc (loc, sqrtfn, 1, arg0);
op = build_call_nofold_loc (loc, sqrtfn, 1, op);
}
/* Optimize pow (x, 0.75) = sqrt (x) * sqrt (sqrt (x)) unless we
are optimizing for space. */
else if (optimize_insn_for_speed_p ()
&& !TREE_SIDE_EFFECTS (arg0)
&& REAL_VALUES_EQUAL (c, dconst3_4))
{
tree sqrt1 = build_call_expr_loc (loc, sqrtfn, 1, arg0);
tree sqrt2 = builtin_save_expr (sqrt1);
tree sqrt3 = build_call_expr_loc (loc, sqrtfn, 1, sqrt1);
op = fold_build2_loc (loc, MULT_EXPR, type, sqrt2, sqrt3);
}
}
}
/* Check whether we can do cbrt insstead of pow (x, 1./3.) and
cbrt/sqrts instead of pow (x, 1./6.). */
if (cbrtfn && ! op
&& (tree_expr_nonnegative_p (arg0) || !HONOR_NANS (mode)))
{
/* First try 1/3. */
REAL_VALUE_TYPE dconst1_3
= real_value_truncate (mode, dconst_third ());
if (REAL_VALUES_EQUAL (c, dconst1_3))
op = build_call_nofold_loc (loc, cbrtfn, 1, arg0);
/* Now try 1/6. */
else if (optimize_insn_for_speed_p ()
&& optab_handler (sqrt_optab, mode) != CODE_FOR_nothing)
{
REAL_VALUE_TYPE dconst1_6 = dconst1_3;
SET_REAL_EXP (&dconst1_6, REAL_EXP (&dconst1_6) - 1);
if (REAL_VALUES_EQUAL (c, dconst1_6))
{
op = build_call_nofold_loc (loc, sqrtfn, 1, arg0);
op = build_call_nofold_loc (loc, cbrtfn, 1, op);
}
}
}
if (op)
return expand_expr (op, subtarget, mode, EXPAND_NORMAL);
}
return NULL_RTX;
}
/* Expand a call to the pow built-in mathematical function. Return NULL_RTX if
a normal call should be emitted rather than expanding the function
in-line. EXP is the expression that is a call to the builtin
function; if convenient, the result should be placed in TARGET. */
static rtx
expand_builtin_pow (tree exp, rtx target, rtx subtarget)
{
tree arg0, arg1;
tree fn, narg0;
tree type = TREE_TYPE (exp);
REAL_VALUE_TYPE cint, c, c2;
HOST_WIDE_INT n;
rtx op, op2;
enum machine_mode mode = TYPE_MODE (type);
if (! validate_arglist (exp, REAL_TYPE, REAL_TYPE, VOID_TYPE))
return NULL_RTX;
arg0 = CALL_EXPR_ARG (exp, 0);
arg1 = CALL_EXPR_ARG (exp, 1);
if (TREE_CODE (arg1) != REAL_CST
|| TREE_OVERFLOW (arg1))
return expand_builtin_mathfn_2 (exp, target, subtarget);
/* Handle constant exponents. */
/* For integer valued exponents we can expand to an optimal multiplication
sequence using expand_powi. */
c = TREE_REAL_CST (arg1);
n = real_to_integer (&c);
real_from_integer (&cint, VOIDmode, n, n < 0 ? -1 : 0, 0);
if (real_identical (&c, &cint)
&& ((n >= -1 && n <= 2)
|| (flag_unsafe_math_optimizations
&& optimize_insn_for_speed_p ()
&& powi_cost (n) <= POWI_MAX_MULTS)))
{
op = expand_expr (arg0, subtarget, VOIDmode, EXPAND_NORMAL);
if (n != 1)
{
op = force_reg (mode, op);
op = expand_powi (op, mode, n);
}
return op;
}
narg0 = builtin_save_expr (arg0);
/* If the exponent is not integer valued, check if it is half of an integer.
In this case we can expand to sqrt (x) * x**(n/2). */
fn = mathfn_built_in (type, BUILT_IN_SQRT);
if (fn != NULL_TREE)
{
real_arithmetic (&c2, MULT_EXPR, &c, &dconst2);
n = real_to_integer (&c2);
real_from_integer (&cint, VOIDmode, n, n < 0 ? -1 : 0, 0);
if (real_identical (&c2, &cint)
&& ((flag_unsafe_math_optimizations
&& optimize_insn_for_speed_p ()
&& powi_cost (n/2) <= POWI_MAX_MULTS)
/* Even the c == 0.5 case cannot be done unconditionally
when we need to preserve signed zeros, as
pow (-0, 0.5) is +0, while sqrt(-0) is -0. */
|| (!HONOR_SIGNED_ZEROS (mode) && n == 1)
/* For c == 1.5 we can assume that x * sqrt (x) is always
smaller than pow (x, 1.5) if sqrt will not be expanded
as a call. */
|| (n == 3
&& optab_handler (sqrt_optab, mode) != CODE_FOR_nothing)))
{
tree call_expr = build_call_nofold_loc (EXPR_LOCATION (exp), fn, 1,
narg0);
/* Use expand_expr in case the newly built call expression
was folded to a non-call. */
op = expand_expr (call_expr, subtarget, mode, EXPAND_NORMAL);
if (n != 1)
{
op2 = expand_expr (narg0, subtarget, VOIDmode, EXPAND_NORMAL);
op2 = force_reg (mode, op2);
op2 = expand_powi (op2, mode, abs (n / 2));
op = expand_simple_binop (mode, MULT, op, op2, NULL_RTX,
0, OPTAB_LIB_WIDEN);
/* If the original exponent was negative, reciprocate the
result. */
if (n < 0)
op = expand_binop (mode, sdiv_optab, CONST1_RTX (mode),
op, NULL_RTX, 0, OPTAB_LIB_WIDEN);
}
return op;
}
}
/* Check whether we can do a series of sqrt or cbrt's instead of the pow
call. */
op = expand_builtin_pow_root (EXPR_LOCATION (exp), arg0, arg1, type,
subtarget);
if (op)
return op;
/* Try if the exponent is a third of an integer. In this case
we can expand to x**(n/3) * cbrt(x)**(n%3). As cbrt (x) is
different from pow (x, 1./3.) due to rounding and behavior
with negative x we need to constrain this transformation to
unsafe math and positive x or finite math. */
fn = mathfn_built_in (type, BUILT_IN_CBRT);
if (fn != NULL_TREE
&& flag_unsafe_math_optimizations
&& (tree_expr_nonnegative_p (arg0)
|| !HONOR_NANS (mode)))
{
REAL_VALUE_TYPE dconst3;
real_from_integer (&dconst3, VOIDmode, 3, 0, 0);
real_arithmetic (&c2, MULT_EXPR, &c, &dconst3);
real_round (&c2, mode, &c2);
n = real_to_integer (&c2);
real_from_integer (&cint, VOIDmode, n, n < 0 ? -1 : 0, 0);
real_arithmetic (&c2, RDIV_EXPR, &cint, &dconst3);
real_convert (&c2, mode, &c2);
if (real_identical (&c2, &c)
&& ((optimize_insn_for_speed_p ()
&& powi_cost (n/3) <= POWI_MAX_MULTS)
|| n == 1))
{
tree call_expr = build_call_nofold_loc (EXPR_LOCATION (exp), fn, 1,
narg0);
op = expand_builtin (call_expr, NULL_RTX, subtarget, mode, 0);
if (abs (n) % 3 == 2)
op = expand_simple_binop (mode, MULT, op, op, op,
0, OPTAB_LIB_WIDEN);
if (n != 1)
{
op2 = expand_expr (narg0, subtarget, VOIDmode, EXPAND_NORMAL);
op2 = force_reg (mode, op2);
op2 = expand_powi (op2, mode, abs (n / 3));
op = expand_simple_binop (mode, MULT, op, op2, NULL_RTX,
0, OPTAB_LIB_WIDEN);
/* If the original exponent was negative, reciprocate the
result. */
if (n < 0)
op = expand_binop (mode, sdiv_optab, CONST1_RTX (mode),
op, NULL_RTX, 0, OPTAB_LIB_WIDEN);
}
return op;
}
}
/* Fall back to optab expansion. */
return expand_builtin_mathfn_2 (exp, target, subtarget);
}
/* Expand a call to the powi built-in mathematical function. Return NULL_RTX if
a normal call should be emitted rather than expanding the function
in-line. EXP is the expression that is a call to the builtin
@ -3288,27 +2843,6 @@ expand_builtin_powi (tree exp, rtx target)
arg1 = CALL_EXPR_ARG (exp, 1);
mode = TYPE_MODE (TREE_TYPE (exp));
/* Handle constant power. */
if (TREE_CODE (arg1) == INTEGER_CST
&& !TREE_OVERFLOW (arg1))
{
HOST_WIDE_INT n = TREE_INT_CST_LOW (arg1);
/* If the exponent is -1, 0, 1 or 2, then expand_powi is exact.
Otherwise, check the number of multiplications required. */
if ((TREE_INT_CST_HIGH (arg1) == 0
|| TREE_INT_CST_HIGH (arg1) == -1)
&& ((n >= -1 && n <= 2)
|| (optimize_insn_for_speed_p ()
&& powi_cost (n) <= POWI_MAX_MULTS)))
{
op0 = expand_expr (arg0, NULL_RTX, VOIDmode, EXPAND_NORMAL);
op0 = force_reg (mode, op0);
return expand_powi (op0, mode, n);
}
}
/* Emit a libcall to libgcc. */
/* Mode of the 2nd argument must match that of an int. */
@ -5862,12 +5396,6 @@ expand_builtin (tree exp, rtx target, rtx subtarget, enum machine_mode mode,
return target;
break;
CASE_FLT_FN (BUILT_IN_POW):
target = expand_builtin_pow (exp, target, subtarget);
if (target)
return target;
break;
CASE_FLT_FN (BUILT_IN_POWI):
target = expand_builtin_powi (exp, target);
if (target)
@ -5885,6 +5413,7 @@ expand_builtin (tree exp, rtx target, rtx subtarget, enum machine_mode mode,
CASE_FLT_FN (BUILT_IN_FMOD):
CASE_FLT_FN (BUILT_IN_REMAINDER):
CASE_FLT_FN (BUILT_IN_DREM):
CASE_FLT_FN (BUILT_IN_POW):
target = expand_builtin_mathfn_2 (exp, target, subtarget);
if (target)
return target;