I suppose people were busy when I posted this patch and it got forgotten since so here is a little ping.
Best regards, Thomas > -----Original Message----- > From: gcc-patches-ow...@gcc.gnu.org [mailto:gcc-patches- > ow...@gcc.gnu.org] On Behalf Of Thomas Preud'homme > Sent: Friday, July 04, 2014 12:53 PM > To: gcc-patches@gcc.gnu.org > Subject: [PATCH] Fix confusion between target, host and symbolic number > byte sizes > > The bswap pass deals with 3 possibly different byte size: host, target and the > size a byte marker occupied in the symbolic_number structure [1]. However, > as of now the code mixes the three size. This works in practice as the pass is > only enabled for target with BITS_PER_UNIT == 8 and nobody runs GCC on a > host with CHAR_BIT != 8. As prompted by Jakub Jelinek, this patch fixes this > mess. Byte marker are 8-bit quantities (they could be made 4-bit quantities > but I prefered to keep the code working the same as before) for which a > new macro is introduced (BITS_PER_MARKERS), anything related to storing > the value or a byte marker in a variable should check for the host byte size > or > wide integer size and anything aimed at manipulating the target value should > check for BITS_PER_UNIT. > > > [1] Although the comment for this structure implies that a byte marker as the > same size as the host byte, the way it is used in the code (even before any of > my patch) shows that it uses a fixed size of 8 [2]. > [2] Note that since the pass is only active for targets with BITS_PER_UNIT == > 8, it might be using the target byte size. > > gcc/ChangeLog: > > 2014-07-04 Thomas Preud'homme <thomas.preudho...@arm.com> > > * tree-ssa-math-opts.c (struct symbolic_number): Clarify comment > about > the size of byte markers. > (do_shift_rotate): Fix confusion between host, target and marker > byte > size. > (verify_symbolic_number_p): Likewise. > (find_bswap_or_nop_1): Likewise. > (find_bswap_or_nop): Likewise. > > > diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c > index ca2b30d..55c5df7 100644 > --- a/gcc/tree-ssa-math-opts.c > +++ b/gcc/tree-ssa-math-opts.c > @@ -1602,11 +1602,10 @@ make_pass_cse_sincos (gcc::context *ctxt) > > /* A symbolic number is used to detect byte permutation and selection > patterns. Therefore the field N contains an artificial number > - consisting of byte size markers: > + consisting of octet sized markers: > > - 0 - byte has the value 0 > - 1..size - byte contains the content of the byte > - number indexed with that value minus one. > + 0 - target byte has the value 0 > + 1..size - marker value is the target byte index minus one. > > To detect permutations on memory sources (arrays and structures), a > symbolic > number is also associated a base address (the array or structure the load > is > @@ -1631,6 +1630,8 @@ struct symbolic_number { > unsigned HOST_WIDE_INT range; > }; > > +#define BITS_PER_MARKER 8 > + > /* The number which the find_bswap_or_nop_1 result should match in > order to have a nop. The number is masked according to the size of > the symbolic number before using it. */ > @@ -1652,15 +1653,16 @@ do_shift_rotate (enum tree_code code, > struct symbolic_number *n, > int count) > { > - int bitsize = TYPE_PRECISION (n->type); > + int size = TYPE_PRECISION (n->type) / BITS_PER_UNIT; > > - if (count % 8 != 0) > + if (count % BITS_PER_UNIT != 0) > return false; > + count = (count / BITS_PER_UNIT) * BITS_PER_MARKER; > > /* Zero out the extra bits of N in order to avoid them being shifted > into the significant bits. */ > - if (bitsize < 8 * (int)sizeof (int64_t)) > - n->n &= ((uint64_t)1 << bitsize) - 1; > + if (size < 64 / BITS_PER_MARKER) > + n->n &= ((uint64_t) 1 << (size * BITS_PER_MARKER)) - 1; > > switch (code) > { > @@ -1670,22 +1672,22 @@ do_shift_rotate (enum tree_code code, > case RSHIFT_EXPR: > /* Arithmetic shift of signed type: result is dependent on the value. > */ > if (!TYPE_UNSIGNED (n->type) > - && (n->n & ((uint64_t) 0xff << (bitsize - 8)))) > + && (n->n & ((uint64_t) 0xff << ((size - 1) * BITS_PER_MARKER)))) > return false; > n->n >>= count; > break; > case LROTATE_EXPR: > - n->n = (n->n << count) | (n->n >> (bitsize - count)); > + n->n = (n->n << count) | (n->n >> ((size * BITS_PER_MARKER) - count)); > break; > case RROTATE_EXPR: > - n->n = (n->n >> count) | (n->n << (bitsize - count)); > + n->n = (n->n >> count) | (n->n << ((size * BITS_PER_MARKER) - count)); > break; > default: > return false; > } > /* Zero unused bits for size. */ > - if (bitsize < 8 * (int)sizeof (int64_t)) > - n->n &= ((uint64_t)1 << bitsize) - 1; > + if (size < 64 / BITS_PER_MARKER) > + n->n &= ((uint64_t) 1 << (size * BITS_PER_MARKER)) - 1; > return true; > } > > @@ -1726,13 +1728,13 @@ init_symbolic_number (struct symbolic_number > *n, tree src) > if (size % BITS_PER_UNIT != 0) > return false; > size /= BITS_PER_UNIT; > - if (size > (int)sizeof (uint64_t)) > + if (size > 64 / BITS_PER_MARKER) > return false; > n->range = size; > n->n = CMPNOP; > > - if (size < (int)sizeof (int64_t)) > - n->n &= ((uint64_t)1 << (size * BITS_PER_UNIT)) - 1; > + if (size < 64 / BITS_PER_MARKER) > + n->n &= ((uint64_t) 1 << (size * BITS_PER_MARKER)) - 1; > > return true; > } > @@ -1870,15 +1872,17 @@ find_bswap_or_nop_1 (gimple stmt, struct > symbolic_number *n, int limit) > case BIT_AND_EXPR: > { > int i, size = TYPE_PRECISION (n->type) / BITS_PER_UNIT; > - uint64_t val = int_cst_value (rhs2); > - uint64_t tmp = val; > + uint64_t val = int_cst_value (rhs2), mask = 0; > + uint64_t tmp = (1 << BITS_PER_UNIT) - 1; > > /* Only constants masking full bytes are allowed. */ > - for (i = 0; i < size; i++, tmp >>= BITS_PER_UNIT) > - if ((tmp & 0xff) != 0 && (tmp & 0xff) != 0xff) > + for (i = 0; i < size; i++, tmp <<= BITS_PER_UNIT) > + if ((val & tmp) != 0 && (val & tmp) != tmp) > return NULL; > + else if (val & tmp) > + mask |= (uint64_t) 0xff << (i * BITS_PER_MARKER); > > - n->n &= val; > + n->n &= mask; > } > break; > case LSHIFT_EXPR: > @@ -1897,25 +1901,27 @@ find_bswap_or_nop_1 (gimple stmt, struct > symbolic_number *n, int limit) > type_size = TYPE_PRECISION (type); > if (type_size % BITS_PER_UNIT != 0) > return NULL; > - if (type_size > (int)sizeof (uint64_t) * 8) > + type_size /= BITS_PER_UNIT; > + if (type_size > 64 / BITS_PER_MARKER) > return NULL; > > /* Sign extension: result is dependent on the value. */ > - old_type_size = TYPE_PRECISION (n->type); > + old_type_size = TYPE_PRECISION (n->type) / BITS_PER_UNIT; > if (!TYPE_UNSIGNED (n->type) > && type_size > old_type_size > - && n->n & ((uint64_t) 0xff << (old_type_size - 8))) > + && n->n & ((uint64_t) 0xff << ((old_type_size - 1) > + * BITS_PER_MARKER))) > return NULL; > > - if (type_size / BITS_PER_UNIT < (int)(sizeof (int64_t))) > + if (type_size < 64 / BITS_PER_MARKER) > { > /* If STMT casts to a smaller type mask out the bits not > belonging to the target type. */ > - n->n &= ((uint64_t)1 << type_size) - 1; > + n->n &= ((uint64_t) 1 << (type_size * BITS_PER_MARKER)) - > 1; > } > n->type = type; > if (!n->base_addr) > - n->range = type_size / BITS_PER_UNIT; > + n->range = type_size; > } > break; > default: > @@ -1965,7 +1971,6 @@ find_bswap_or_nop_1 (gimple stmt, struct > symbolic_number *n, int limit) > != gimple_assign_rhs1 (source_stmt2)) > { > int64_t inc, mask; > - unsigned i; > HOST_WIDE_INT off_sub; > struct symbolic_number *n_ptr; > > @@ -1989,21 +1994,23 @@ find_bswap_or_nop_1 (gimple stmt, struct > symbolic_number *n, int limit) > > off_sub = n2.bytepos - n1.bytepos; > > - /* Check that the range of memory covered < biggest int size. */ > - if (off_sub + n2.range > (int) sizeof (int64_t)) > + /* Check that the range of memory covered can be represented > by > + a symbolic number. */ > + if (off_sub + n2.range > 64 / BITS_PER_MARKER) > return NULL; > n->range = n2.range + off_sub; > > /* Reinterpret byte marks in symbolic number holding the value > of > bigger weight according to target endianness. */ > inc = BYTES_BIG_ENDIAN ? off_sub + n2.range - n1.range : > off_sub; > - mask = 0xFF; > + size = TYPE_PRECISION (n1.type) / BITS_PER_UNIT; > + mask = 0xff; > if (BYTES_BIG_ENDIAN) > n_ptr = &n1; > else > n_ptr = &n2; > - for (i = 0; i < sizeof (int64_t); i++, inc <<= 8, > - mask <<= 8) > + for (i = 0; i < size; i++, inc <<= BITS_PER_MARKER, > + mask <<= BITS_PER_MARKER) > { > if (n_ptr->n & mask) > n_ptr->n += inc; > @@ -2023,7 +2030,7 @@ find_bswap_or_nop_1 (gimple stmt, struct > symbolic_number *n, int limit) > n->bytepos = n1.bytepos; > n->type = n1.type; > size = TYPE_PRECISION (n->type) / BITS_PER_UNIT; > - for (i = 0, mask = 0xff; i < size; i++, mask <<= BITS_PER_UNIT) > + for (i = 0, mask = 0xff; i < size; i++, mask <<= BITS_PER_MARKER) > { > uint64_t masked1, masked2; > > @@ -2084,17 +2091,17 @@ find_bswap_or_nop (gimple stmt, struct > symbolic_number *n, bool *bswap) > int rsize; > uint64_t tmpn; > > - for (tmpn = n->n, rsize = 0; tmpn; tmpn >>= BITS_PER_UNIT, rsize++); > + for (tmpn = n->n, rsize = 0; tmpn; tmpn >>= BITS_PER_MARKER, rsize++); > n->range = rsize; > } > > /* Zero out the extra bits of N and CMP*. */ > - if (n->range < (int)sizeof (int64_t)) > + if (n->range < (int) sizeof (int64_t)) > { > uint64_t mask; > > - mask = ((uint64_t)1 << (n->range * BITS_PER_UNIT)) - 1; > - cmpxchg >>= (sizeof (int64_t) - n->range) * BITS_PER_UNIT; > + mask = ((uint64_t) 1 << (n->range * BITS_PER_MARKER)) - 1; > + cmpxchg >>= (64 / BITS_PER_MARKER - n->range) * BITS_PER_MARKER; > cmpnop &= mask; > } > > Ok for trunk? > > Best regards, > > Thomas > >
