[PATCH] MPILIB: Provide count_leading/trailing_zeros() based on archfunctions
From: David Howells
Date: Fri Jul 06 2012 - 11:45:31 EST
Provide count_leading/trailing_zeros() macros based on extant arch bit scanning
functions rather than reimplementing from scratch in MPILIB.
Whilst we're at it, turn count_foo_zeros(n, x) into n = count_foo_zeros(x).
Also move the definition to asm-generic as other people may be interested in
using it.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxxx>
---
include/asm-generic/bitops/count_zeros.h | 57 ++++++++++++
lib/mpi/longlong.h | 138 ------------------------------
lib/mpi/mpi-bit.c | 2
lib/mpi/mpi-div.c | 2
lib/mpi/mpi-pow.c | 4 -
lib/mpi/mpi-scan.c | 2
lib/mpi/mpih-div.c | 8 +-
7 files changed, 68 insertions(+), 145 deletions(-)
create mode 100644 include/asm-generic/bitops/count_zeros.h
diff --git a/include/asm-generic/bitops/count_zeros.h b/include/asm-generic/bitops/count_zeros.h
new file mode 100644
index 0000000..97520d2
--- /dev/null
+++ b/include/asm-generic/bitops/count_zeros.h
@@ -0,0 +1,57 @@
+/* Count leading and trailing zeros functions
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_
+#define _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_
+
+#include <asm/bitops.h>
+
+/**
+ * count_leading_zeros - Count the number of zeros from the MSB back
+ * @x: The value
+ *
+ * Count the number of leading zeros from the MSB going towards the LSB in @x.
+ *
+ * If the MSB of @x is set, the result is 0.
+ * If only the LSB of @x is set, then the result is BITS_PER_LONG-1.
+ * If @x is 0 then the result is COUNT_LEADING_ZEROS_0.
+ */
+static inline int count_leading_zeros(unsigned long x)
+{
+ if (sizeof(x) == 4)
+ return BITS_PER_LONG - fls(x);
+ else
+ return BITS_PER_LONG - fls64(x);
+}
+
+#define COUNT_LEADING_ZEROS_0 BITS_PER_LONG
+
+/**
+ * count_trailing_zeros - Count the number of zeros from the LSB forwards
+ * @x: The value
+ *
+ * Count the number of trailing zeros from the LSB going towards the MSB in @x.
+ *
+ * If the LSB of @x is set, the result is 0.
+ * If only the MSB of @x is set, then the result is BITS_PER_LONG-1.
+ * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0.
+ */
+static inline int count_trailing_zeros(unsigned long x)
+{
+#define COUNT_TRAILING_ZEROS_0 (-1)
+
+ if (sizeof(x) == 4)
+ return ffs(x);
+ else
+ return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0;
+}
+
+#endif /* _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ */
diff --git a/lib/mpi/longlong.h b/lib/mpi/longlong.h
index 29f9862..678ce4f 100644
--- a/lib/mpi/longlong.h
+++ b/lib/mpi/longlong.h
@@ -19,6 +19,8 @@
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA. */
+#include <asm-generic/bitops/count_zeros.h>
+
/* You have to define the following before including this file:
*
* UWtype -- An unsigned type, default type for operations (typically a "word")
@@ -146,12 +148,6 @@ do { \
: "1" ((USItype)(n1)), \
"r" ((USItype)(n0)), \
"r" ((USItype)(d)))
-
-#define count_leading_zeros(count, x) \
- __asm__ ("clz %0,%1" \
- : "=r" ((USItype)(count)) \
- : "r" ((USItype)(x)))
-#define COUNT_LEADING_ZEROS_0 32
#endif /* __a29k__ */
#if defined(__alpha) && W_TYPE_SIZE == 64
@@ -298,11 +294,6 @@ extern UDItype __udiv_qrnnd();
: "1" ((USItype)(nh)), \
"0" ((USItype)(nl)), \
"g" ((USItype)(d)))
-#define count_leading_zeros(count, x) \
- __asm__ ("bsch/1 %1,%0" \
- : "=g" (count) \
- : "g" ((USItype)(x)), \
- "0" ((USItype)0))
#endif
/***************************************
@@ -354,27 +345,6 @@ do { USItype __r; \
} while (0)
extern USItype __udiv_qrnnd();
#endif /* LONGLONG_STANDALONE */
-#define count_leading_zeros(count, x) \
-do { \
- USItype __tmp; \
- __asm__ ( \
- "ldi 1,%0\n" \
- "extru,= %1,15,16,%%r0 ; Bits 31..16 zero?\n" \
- "extru,tr %1,15,16,%1 ; No. Shift down, skip add.\n" \
- "ldo 16(%0),%0 ; Yes. Perform add.\n" \
- "extru,= %1,23,8,%%r0 ; Bits 15..8 zero?\n" \
- "extru,tr %1,23,8,%1 ; No. Shift down, skip add.\n" \
- "ldo 8(%0),%0 ; Yes. Perform add.\n" \
- "extru,= %1,27,4,%%r0 ; Bits 7..4 zero?\n" \
- "extru,tr %1,27,4,%1 ; No. Shift down, skip add.\n" \
- "ldo 4(%0),%0 ; Yes. Perform add.\n" \
- "extru,= %1,29,2,%%r0 ; Bits 3..2 zero?\n" \
- "extru,tr %1,29,2,%1 ; No. Shift down, skip add.\n" \
- "ldo 2(%0),%0 ; Yes. Perform add.\n" \
- "extru %1,30,1,%1 ; Extract bit 1.\n" \
- "sub %0,%1,%0 ; Subtract it. " \
- : "=r" (count), "=r" (__tmp) : "1" (x)); \
-} while (0)
#endif /* hppa */
/***************************************
@@ -457,15 +427,6 @@ do { \
: "0" ((USItype)(n0)), \
"1" ((USItype)(n1)), \
"rm" ((USItype)(d)))
-#define count_leading_zeros(count, x) \
-do { \
- USItype __cbtmp; \
- __asm__ ("bsrl %1,%0" \
- : "=r" (__cbtmp) : "rm" ((USItype)(x))); \
- (count) = __cbtmp ^ 31; \
-} while (0)
-#define count_trailing_zeros(count, x) \
- __asm__ ("bsfl %1,%0" : "=r" (count) : "rm" ((USItype)(x)))
#ifndef UMUL_TIME
#define UMUL_TIME 40
#endif
@@ -536,15 +497,6 @@ do { \
"dI" ((USItype)(d))); \
(r) = __rq.__i.__l; (q) = __rq.__i.__h; \
} while (0)
-#define count_leading_zeros(count, x) \
-do { \
- USItype __cbtmp; \
- __asm__ ("scanbit %1,%0" \
- : "=r" (__cbtmp) \
- : "r" ((USItype)(x))); \
- (count) = __cbtmp ^ 31; \
-} while (0)
-#define COUNT_LEADING_ZEROS_0 (-32) /* sic */
#if defined(__i960mx) /* what is the proper symbol to test??? */
#define rshift_rhlc(r, h, l, c) \
do { \
@@ -603,11 +555,6 @@ do { \
: "0" ((USItype)(n0)), \
"1" ((USItype)(n1)), \
"dmi" ((USItype)(d)))
-#define count_leading_zeros(count, x) \
- __asm__ ("bfffo %1{%b2:%b2},%0" \
- : "=d" ((USItype)(count)) \
- : "od" ((USItype)(x)), "n" (0))
-#define COUNT_LEADING_ZEROS_0 32
#else /* not mc68020 */
#define umul_ppmm(xh, xl, a, b) \
do { USItype __umul_tmp1, __umul_tmp2; \
@@ -664,15 +611,6 @@ do { USItype __umul_tmp1, __umul_tmp2; \
"rJ" ((USItype)(bh)), \
"rJ" ((USItype)(al)), \
"rJ" ((USItype)(bl)))
-#define count_leading_zeros(count, x) \
-do { \
- USItype __cbtmp; \
- __asm__ ("ff1 %0,%1" \
- : "=r" (__cbtmp) \
- : "r" ((USItype)(x))); \
- (count) = __cbtmp ^ 31; \
-} while (0)
-#define COUNT_LEADING_ZEROS_0 63 /* sic */
#if defined(__m88110__)
#define umul_ppmm(wh, wl, u, v) \
do { \
@@ -779,12 +717,6 @@ do { \
: "0" (__xx.__ll), \
"g" ((USItype)(d))); \
(r) = __xx.__i.__l; (q) = __xx.__i.__h; })
-#define count_trailing_zeros(count, x) \
-do { \
- __asm__("ffsd %2,%0" \
- : "=r"((USItype) (count)) \
- : "0"((USItype) 0), "r"((USItype) (x))); \
- } while (0)
#endif /* __ns32000__ */
/***************************************
@@ -855,11 +787,6 @@ do { \
"rI" ((USItype)(al)), \
"r" ((USItype)(bl))); \
} while (0)
-#define count_leading_zeros(count, x) \
- __asm__ ("{cntlz|cntlzw} %0,%1" \
- : "=r" ((USItype)(count)) \
- : "r" ((USItype)(x)))
-#define COUNT_LEADING_ZEROS_0 32
#if defined(_ARCH_PPC)
#define umul_ppmm(ph, pl, m0, m1) \
do { \
@@ -1001,19 +928,6 @@ do { \
} while (0)
#define UMUL_TIME 20
#define UDIV_TIME 200
-#define count_leading_zeros(count, x) \
-do { \
- if ((x) >= 0x10000) \
- __asm__ ("clz %0,%1" \
- : "=r" ((USItype)(count)) \
- : "r" ((USItype)(x) >> 16)); \
- else { \
- __asm__ ("clz %0,%1" \
- : "=r" ((USItype)(count)) \
- : "r" ((USItype)(x))); \
- (count) += 16; \
- } \
-} while (0)
#endif /* RT/ROMP */
/***************************************
@@ -1142,13 +1056,6 @@ do { \
"rI" ((USItype)(d)) \
: "%g1" __AND_CLOBBER_CC)
#define UDIV_TIME 37
-#define count_leading_zeros(count, x) \
- __asm__ ("scan %1,0,%0" \
- : "=r" ((USItype)(x)) \
- : "r" ((USItype)(count)))
-/* Early sparclites return 63 for an argument of 0, but they warn that future
- implementations might change this. Therefore, leave COUNT_LEADING_ZEROS_0
- undefined. */
#endif /* __sparclite__ */
#endif /* __sparc_v8__ */
/* Default to sparc v7 versions of umul_ppmm and udiv_qrnnd. */
@@ -1454,47 +1361,6 @@ do { \
#define udiv_qrnnd __udiv_qrnnd_c
#endif
-#undef count_leading_zeros
-#if !defined(count_leading_zeros)
- extern
-#ifdef __STDC__
- const
-#endif
- unsigned char __clz_tab[];
-#define count_leading_zeros(count, x) \
-do { \
- UWtype __xr = (x); \
- UWtype __a; \
- \
- if (W_TYPE_SIZE <= 32) { \
- __a = __xr < ((UWtype) 1 << 2*__BITS4) \
- ? (__xr < ((UWtype) 1 << __BITS4) ? 0 : __BITS4) \
- : (__xr < ((UWtype) 1 << 3*__BITS4) ? 2*__BITS4 : 3*__BITS4); \
- } \
- else { \
- for (__a = W_TYPE_SIZE - 8; __a > 0; __a -= 8) \
- if (((__xr >> __a) & 0xff) != 0) \
- break; \
- } \
- \
- (count) = W_TYPE_SIZE - (__clz_tab[__xr >> __a] + __a); \
-} while (0)
- /* This version gives a well-defined value for zero. */
-#define COUNT_LEADING_ZEROS_0 W_TYPE_SIZE
-#endif
-
-#if !defined(count_trailing_zeros)
-/* Define count_trailing_zeros using count_leading_zeros. The latter might be
- defined in asm, but if it is not, the C version above is good enough. */
-#define count_trailing_zeros(count, x) \
-do { \
- UWtype __ctz_x = (x); \
- UWtype __ctz_c; \
- count_leading_zeros(__ctz_c, __ctz_x & -__ctz_x); \
- (count) = W_TYPE_SIZE - 1 - __ctz_c; \
-} while (0)
-#endif
-
#ifndef UDIV_NEEDS_NORMALIZATION
#define UDIV_NEEDS_NORMALIZATION 0
#endif
diff --git a/lib/mpi/mpi-bit.c b/lib/mpi/mpi-bit.c
index 0c50536..3fc00bf 100644
--- a/lib/mpi/mpi-bit.c
+++ b/lib/mpi/mpi-bit.c
@@ -45,7 +45,7 @@ unsigned mpi_get_nbits(MPI a)
if (a->nlimbs) {
mpi_limb_t alimb = a->d[a->nlimbs - 1];
if (alimb)
- count_leading_zeros(n, alimb);
+ n = count_leading_zeros(alimb);
else
n = BITS_PER_MPI_LIMB;
n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;
diff --git a/lib/mpi/mpi-div.c b/lib/mpi/mpi-div.c
index f68cbbb..51f105c 100644
--- a/lib/mpi/mpi-div.c
+++ b/lib/mpi/mpi-div.c
@@ -217,7 +217,7 @@ int mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den)
} else /* Put quotient at top of remainder. */
qp = rp + dsize;
- count_leading_zeros(normalization_steps, dp[dsize - 1]);
+ normalization_steps = count_leading_zeros(dp[dsize - 1]);
/* Normalize the denominator, i.e. make its most significant bit set by
* shifting it NORMALIZATION_STEPS bits to the left. Also shift the
diff --git a/lib/mpi/mpi-pow.c b/lib/mpi/mpi-pow.c
index 67f3e79..5464c87 100644
--- a/lib/mpi/mpi-pow.c
+++ b/lib/mpi/mpi-pow.c
@@ -77,7 +77,7 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
mp = mp_marker = mpi_alloc_limb_space(msize);
if (!mp)
goto enomem;
- count_leading_zeros(mod_shift_cnt, mod->d[msize - 1]);
+ mod_shift_cnt = count_leading_zeros(mod->d[msize - 1]);
if (mod_shift_cnt)
mpihelp_lshift(mp, mod->d, msize, mod_shift_cnt);
else
@@ -169,7 +169,7 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
i = esize - 1;
e = ep[i];
- count_leading_zeros(c, e);
+ c = count_leading_zeros(e);
e = (e << c) << 1; /* shift the exp bits to the left, lose msb */
c = BITS_PER_MPI_LIMB - 1 - c;
diff --git a/lib/mpi/mpi-scan.c b/lib/mpi/mpi-scan.c
index b2da5ad..58556b5 100644
--- a/lib/mpi/mpi-scan.c
+++ b/lib/mpi/mpi-scan.c
@@ -125,7 +125,7 @@ unsigned mpi_trailing_zeros(const MPI a)
unsigned nn;
mpi_limb_t alimb = a->d[n];
- count_trailing_zeros(nn, alimb);
+ nn = count_trailing_zeros(alimb);
count += nn;
break;
}
diff --git a/lib/mpi/mpih-div.c b/lib/mpi/mpih-div.c
index cde1aae..d6483792 100644
--- a/lib/mpi/mpih-div.c
+++ b/lib/mpi/mpih-div.c
@@ -65,7 +65,7 @@ mpihelp_mod_1(mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME) {
int normalization_steps;
- count_leading_zeros(normalization_steps, divisor_limb);
+ normalization_steps = count_leading_zeros(divisor_limb);
if (normalization_steps) {
mpi_limb_t divisor_limb_inverted;
@@ -142,7 +142,7 @@ mpihelp_mod_1(mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
if (UDIV_NEEDS_NORMALIZATION) {
int normalization_steps;
- count_leading_zeros(normalization_steps, divisor_limb);
+ normalization_steps = count_leading_zeros(divisor_limb);
if (normalization_steps) {
divisor_limb <<= normalization_steps;
@@ -421,7 +421,7 @@ mpihelp_divmod_1(mpi_ptr_t quot_ptr,
&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME) {
int normalization_steps;
- count_leading_zeros(normalization_steps, divisor_limb);
+ normalization_steps = count_leading_zeros(divisor_limb);
if (normalization_steps) {
mpi_limb_t divisor_limb_inverted;
@@ -496,7 +496,7 @@ mpihelp_divmod_1(mpi_ptr_t quot_ptr,
if (UDIV_NEEDS_NORMALIZATION) {
int normalization_steps;
- count_leading_zeros(normalization_steps, divisor_limb);
+ normalization_steps = count_leading_zeros(divisor_limb);
if (normalization_steps) {
divisor_limb <<= normalization_steps;
--
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