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Replace exact_log2(x & -x) in favor of more direct computation.

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* toplev.h (ctz_hwi, clz_hwi, ffs_hwi): New.
	(floor_log2): Use clz_hwi.
	(exact_log2): Use ctz_hwi.
	* toplev.c (ctz_hwi, clz_hwi, ffs_hwi): New.
	* builtins.c (fold_builtin_bitop): Use them.
	* simplify-rtx.c (simplify_const_unary_operation): Likewise.
	* combine.c (get_pos_from_mask): Use ctz_hwi.
	* double-int.c (double_int_ctz): Likewise.
	* explow.c (force_reg): Likewise.
	* tree.h (SET_DECL_OFFSET_ALIGN): Use ffs_hwi.

From-SVN: r162920
This commit is contained in:
Richard Henderson 2010-08-05 12:41:31 -07:00 committed by Richard Henderson
parent 55b324a67c
commit bd95721f86
9 changed files with 109 additions and 47 deletions
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13
gcc/ChangeLog
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@ -1,3 +1,16 @@
2010-08-05 Richard Henderson <rth@redhat.com>
* toplev.h (ctz_hwi, clz_hwi, ffs_hwi): New.
(floor_log2): Use clz_hwi.
(exact_log2): Use ctz_hwi.
* toplev.c (ctz_hwi, clz_hwi, ffs_hwi): New.
* builtins.c (fold_builtin_bitop): Use them.
* simplify-rtx.c (simplify_const_unary_operation): Likewise.
* combine.c (get_pos_from_mask): Use ctz_hwi.
* double-int.c (double_int_ctz): Likewise.
* explow.c (force_reg): Likewise.
* tree.h (SET_DECL_OFFSET_ALIGN): Use ffs_hwi.
2010-08-05 Richard Henderson <rth@redhat.com>
PR target/45189

12
gcc/builtins.c
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@ -7676,9 +7676,9 @@ fold_builtin_bitop (tree fndecl, tree arg)
{
CASE_INT_FN (BUILT_IN_FFS):
if (lo != 0)
result = exact_log2 (lo & -lo) + 1;
result = ffs_hwi (lo);
else if (hi != 0)
result = HOST_BITS_PER_WIDE_INT + exact_log2 (hi & -hi) + 1;
result = HOST_BITS_PER_WIDE_INT + ffs_hwi (hi);
else
result = 0;
break;
@ -7694,9 +7694,9 @@ fold_builtin_bitop (tree fndecl, tree arg)
CASE_INT_FN (BUILT_IN_CTZ):
if (lo != 0)
result = exact_log2 (lo & -lo);
result = ctz_hwi (lo);
else if (hi != 0)
result = HOST_BITS_PER_WIDE_INT + exact_log2 (hi & -hi);
result = HOST_BITS_PER_WIDE_INT + ctz_hwi (hi);
else if (! CTZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (type), result))
result = width;
break;
@ -7706,7 +7706,7 @@ fold_builtin_bitop (tree fndecl, tree arg)
while (lo)
result++, lo &= lo - 1;
while (hi)
result++, hi &= hi - 1;
result++, hi &= (unsigned HOST_WIDE_INT) hi - 1;
break;
CASE_INT_FN (BUILT_IN_PARITY):
@ -7714,7 +7714,7 @@ fold_builtin_bitop (tree fndecl, tree arg)
while (lo)
result++, lo &= lo - 1;
while (hi)
result++, hi &= hi - 1;
result++, hi &= (unsigned HOST_WIDE_INT) hi - 1;
result &= 1;
break;

2
gcc/combine.c
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@ -7436,7 +7436,7 @@ static int
get_pos_from_mask (unsigned HOST_WIDE_INT m, unsigned HOST_WIDE_INT *plen)
{
/* Get the bit number of the first 1 bit from the right, -1 if none. */
int pos = exact_log2 (m & -m);
int pos = m ? ctz_hwi (m) : -1;
int len = 0;
if (pos >= 0)

10
gcc/double-int.c
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@ -859,15 +859,7 @@ double_int_ctz (double_int a)
unsigned bits = a.low ? 0 : HOST_BITS_PER_WIDE_INT;
if (!w)
return HOST_BITS_PER_DOUBLE_INT;
#if (GCC_VERSION >= 3004)
bits += CTZ_HWI (w);
#else
while (!(w & 1))
{
w >>= 1;
bits += 1;
}
#endif
bits += ctz_hwi (w);
return bits;
}

10
gcc/explow.c
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@ -707,9 +707,13 @@ force_reg (enum machine_mode mode, rtx x)
if (SYMBOL_REF_DECL (s) && DECL_P (SYMBOL_REF_DECL (s)))
sa = DECL_ALIGN (SYMBOL_REF_DECL (s));
ca = exact_log2 (INTVAL (c) & -INTVAL (c)) * BITS_PER_UNIT;
align = MIN (sa, ca);
if (INTVAL (c) == 0)
align = sa;
else
{
ca = ctz_hwi (INTVAL (c)) * BITS_PER_UNIT;
align = MIN (sa, ca);
}
}
if (align || (MEM_P (x) && MEM_POINTER (x)))

23
gcc/simplify-rtx.c
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@ -1197,10 +1197,8 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode,
break;
case FFS:
/* Don't use ffs here. Instead, get low order bit and then its
number. If arg0 is zero, this will return 0, as desired. */
arg0 &= GET_MODE_MASK (mode);
val = exact_log2 (arg0 & (- arg0)) + 1;
val = ffs_hwi (arg0);
break;
case CLZ:
@ -1221,7 +1219,7 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode,
val = GET_MODE_BITSIZE (mode);
}
else
val = exact_log2 (arg0 & -arg0);
val = ctz_hwi (arg0);
break;
case POPCOUNT:
@ -1351,15 +1349,12 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode,
case FFS:
hv = 0;
if (l1 == 0)
{
if (h1 == 0)
lv = 0;
else
lv = HOST_BITS_PER_WIDE_INT + exact_log2 (h1 & -h1) + 1;
}
if (l1 != 0)
lv = ffs_hwi (l1);
else if (h1 != 0)
lv = HOST_BITS_PER_WIDE_INT + ffs_hwi (h1);
else
lv = exact_log2 (l1 & -l1) + 1;
lv = 0;
break;
case CLZ:
@ -1376,9 +1371,9 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode,
case CTZ:
hv = 0;
if (l1 != 0)
lv = exact_log2 (l1 & -l1);
lv = ctz_hwi (l1);
else if (h1 != 0)
lv = HOST_BITS_PER_WIDE_INT + exact_log2 (h1 & -h1);
lv = HOST_BITS_PER_WIDE_INT + ctz_hwi (h1);
else if (! CTZ_DEFINED_VALUE_AT_ZERO (mode, lv))
lv = GET_MODE_BITSIZE (mode);
break;

32
gcc/toplev.c
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@ -484,9 +484,9 @@ set_random_seed (const char *val)
#if GCC_VERSION < 3004
/* The functions floor_log2 and exact_log2 are defined as inline
functions in toplev.h if GCC_VERSION >= 3004. The definitions here
are used for older versions of gcc. */
/* The functions clz_hwi, ctz_hwi, ffs_hwi, floor_log2 and exact_log2
are defined as inline functions in toplev.h if GCC_VERSION >= 3004.
The definitions here are used for older versions of gcc. */
/* Given X, an unsigned number, return the largest int Y such that 2**Y <= X.
If X is 0, return -1. */
@ -530,6 +530,32 @@ exact_log2 (unsigned HOST_WIDE_INT x)
return floor_log2 (x);
}
/* Given X, an unsigned number, return the number of least significant bits
that are zero. When X == 0, the result is the word size. */
int
ctz_hwi (unsigned HOST_WIDE_INT x)
{
return x ? floor_log2 (x & -x) : HOST_BITS_PER_WIDE_INT;
}
/* Similarly for most significant bits. */
int
clz_hwi (unsigned HOST_WIDE_INT x)
{
return HOST_BITS_PER_WIDE_INT - 1 - floor_log2(x);
}
/* Similar to ctz_hwi, except that the least significant bit is numbered
starting from 1, and X == 0 yields 0. */
int
ffs_hwi (unsigned HOST_WIDE_INT x)
{
return 1 + floor_log2 (x & -x);
}
#endif /* GCC_VERSION < 3004 */
/* Handler for fatal signals, such as SIGSEGV. These are transformed

50
gcc/toplev.h
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@ -111,6 +111,10 @@ extern bool fast_math_flags_struct_set_p (struct cl_optimization *);
/* Inline versions of the above for speed. */
#if GCC_VERSION < 3004
extern int clz_hwi (unsigned HOST_WIDE_INT x);
extern int ctz_hwi (unsigned HOST_WIDE_INT x);
extern int ffs_hwi (unsigned HOST_WIDE_INT x);
/* Return log2, or -1 if not exact. */
extern int exact_log2 (unsigned HOST_WIDE_INT);
@ -119,27 +123,57 @@ extern int floor_log2 (unsigned HOST_WIDE_INT);
#else /* GCC_VERSION >= 3004 */
/* For convenience, define 0 -> word_size. */
static inline int
clz_hwi (unsigned HOST_WIDE_INT x)
{
if (x == 0)
return HOST_BITS_PER_WIDE_INT;
# if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONG
# define CLZ_HWI __builtin_clzl
# define CTZ_HWI __builtin_ctzl
return __builtin_clzl (x);
# elif HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONGLONG
# define CLZ_HWI __builtin_clzll
# define CTZ_HWI __builtin_ctzll
return __builtin_clzll (x);
# else
# define CLZ_HWI __builtin_clz
# define CTZ_HWI __builtin_ctz
return __builtin_clz (x);
# endif
}
static inline int
ctz_hwi (unsigned HOST_WIDE_INT x)
{
if (x == 0)
return HOST_BITS_PER_WIDE_INT;
# if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONG
return __builtin_ctzl (x);
# elif HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONGLONG
return __builtin_ctzll (x);
# else
return __builtin_ctz (x);
# endif
}
static inline int
ffs_hwi (unsigned HOST_WIDE_INT x)
{
# if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONG
return __builtin_ffsl (x);
# elif HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONGLONG
return __builtin_ffsll (x);
# else
return __builtin_ffs (x);
# endif
}
static inline int
floor_log2 (unsigned HOST_WIDE_INT x)
{
return x ? HOST_BITS_PER_WIDE_INT - 1 - (int) CLZ_HWI (x) : -1;
return HOST_BITS_PER_WIDE_INT - 1 - clz_hwi (x);
}
static inline int
exact_log2 (unsigned HOST_WIDE_INT x)
{
return x == (x & -x) && x ? (int) CTZ_HWI (x) : -1;
return x == (x & -x) && x ? ctz_hwi (x) : -1;
}
#endif /* GCC_VERSION >= 3004 */

4
gcc/tree.h
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@ -2850,9 +2850,7 @@ struct GTY(()) tree_decl_with_rtl {
/* Specify that DECL_ALIGN(NODE) is a multiple of X. */
#define SET_DECL_OFFSET_ALIGN(NODE, X) \
(FIELD_DECL_CHECK (NODE)->decl_common.off_align = exact_log2 ((X) & -(X)))
/* 1 if the alignment for this type was requested by "aligned" attribute,
0 if it is the default for this type. */
(FIELD_DECL_CHECK (NODE)->decl_common.off_align = ffs_hwi (X) - 1)
/* For FIELD_DECLS, DECL_FCONTEXT is the *first* baseclass in
which this FIELD_DECL is defined. This information is needed when