Xianmiao Qu <cooper...@linux.alibaba.com> writes:
> With the increase in the number of modes and patterns for some
> backend architectures, the place_operands function becomes a
> bottleneck int the speed of genoutput, and may even become a
> bottleneck int the overall speed of building the GCC project.
> This patch aims to accelerate the place_operands function,
> the optimizations it includes are:
> 1. Use a hash table to store operand information,
> improving the lookup time for the first operand.
> 2. Move mode comparison to the beginning to avoid the scenarios of most
> strcmp.
>
> I tested the speed improvements for the following backends,
> Improvement Ratio
> x86_64 197.9%
> aarch64 954.5%
> riscv 2578.6%
> If the build machine is slow, then this improvement can save a lot of time.
>
> I tested the genoutput output for x86_64/aarch64/riscv backends,
> and there was no difference compared to before the optimization,
> so this shouldn't introduce any functional issues.
>
> gcc/
> * genoutput.cc (struct operand_data): Add member 'eq_next' to
> point to the next member with the same hash value in the
> hash table.
> (compare_operands): Move the comparison of the mode to the very
> beginning to accelerate the comparison of the two operands.
> (struct operand_data_hasher): New, a class that takes into account
> the necessary elements for comparing the equality of two operands
> in its hash value.
> (operand_data_hasher::hash): New.
> (operand_data_hasher::equal): New.
> (operand_datas): New, hash table of konwn pattern operands.
> (place_operands): Use a hash table instead of traversing the array
> to find the same operand.
> (main): Add initialization of the hash table 'operand_datas'.
> ---
> gcc/genoutput.cc | 105 ++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 85 insertions(+), 20 deletions(-)
>
> diff --git a/gcc/genoutput.cc b/gcc/genoutput.cc
> index efd81766bb5b..cca1b6622d47 100644
> --- a/gcc/genoutput.cc
> +++ b/gcc/genoutput.cc
> @@ -91,6 +91,7 @@ along with GCC; see the file COPYING3. If not see
> #include "errors.h"
> #include "read-md.h"
> #include "gensupport.h"
> +#include "hash-table.h"
>
> /* No instruction can have more operands than this. Sorry for this
> arbitrary limit, but what machine will have an instruction with
> @@ -112,6 +113,8 @@ static int next_operand_number = 1;
> struct operand_data
> {
> struct operand_data *next;
> + /* Point to the next member with the same hash value in the hash table. */
> + struct operand_data *eq_next;
> int index;
> const char *predicate;
> const char *constraint;
> @@ -127,7 +130,7 @@ struct operand_data
>
> static struct operand_data null_operand =
> {
> - 0, 0, "", "", E_VOIDmode, 0, 0, 0, 0, 0
> + 0, 0, 0, "", "", E_VOIDmode, 0, 0, 0, 0, 0
> };
>
> static struct operand_data *odata = &null_operand;
> @@ -532,6 +535,13 @@ compare_operands (struct operand_data *d0, struct
> operand_data *d1)
> {
Did the const change Richard suggested not work?
(Also, note that he said it's fine to commit once his suggested changes
are made.)
> [...]
thanks,
samOA
