| Message ID | 1479135786-31150-4-git-send-email-arnez@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
On 11/14/2016 09:02 AM, Andreas Arnez wrote: > The function copy_bitwise used for copying DWARF pieces can potentially > be invoked for large chunks of data. For instance, consider a large > struct one of whose members is currently located in a register. In this > case copy_bitwise would still copy the data bitwise in a loop, which is > much slower than necessary. > > This change uses memcpy for the large part instead, if possible. > > gdb/ChangeLog: > > * dwarf2loc.c (copy_bitwise): Use memcpy for the middle part, if > it is byte-aligned. > --- > gdb/dwarf2loc.c | 27 +++++++++++++++++++++++---- > 1 file changed, 23 insertions(+), 4 deletions(-) > > diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c > index 3a241a8..26f6bd8 100644 > --- a/gdb/dwarf2loc.c > +++ b/gdb/dwarf2loc.c > @@ -1547,11 +1547,30 @@ copy_bitwise (gdb_byte *dest, ULONGEST dest_offset, > { > size_t len = nbits / 8; > > - while (len--) > + /* Use a faster method for byte-aligned copies. */ > + if (avail == 0) > { > - buf |= *(bits_big_endian ? source-- : source++) << avail; > - *(bits_big_endian ? dest-- : dest++) = buf; > - buf >>= 8; > + if (bits_big_endian) > + { > + dest -= len; > + source -= len; > + memcpy (dest + 1, source + 1, len); > + } > + else > + { > + memcpy (dest, source, len); > + dest += len; > + source += len; > + } > + } > + else > + { > + while (len--) > + { > + buf |= *(bits_big_endian ? source-- : source++) << avail; Same as patch 2/3 about the construct. > + *(bits_big_endian ? dest-- : dest++) = buf; > + buf >>= 8; > + } > } > nbits %= 8; > } > Otherwise looks sane to me.
diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c index 3a241a8..26f6bd8 100644 --- a/gdb/dwarf2loc.c +++ b/gdb/dwarf2loc.c @@ -1547,11 +1547,30 @@ copy_bitwise (gdb_byte *dest, ULONGEST dest_offset, { size_t len = nbits / 8; - while (len--) + /* Use a faster method for byte-aligned copies. */ + if (avail == 0) { - buf |= *(bits_big_endian ? source-- : source++) << avail; - *(bits_big_endian ? dest-- : dest++) = buf; - buf >>= 8; + if (bits_big_endian) + { + dest -= len; + source -= len; + memcpy (dest + 1, source + 1, len); + } + else + { + memcpy (dest, source, len); + dest += len; + source += len; + } + } + else + { + while (len--) + { + buf |= *(bits_big_endian ? source-- : source++) << avail; + *(bits_big_endian ? dest-- : dest++) = buf; + buf >>= 8; + } } nbits %= 8; }