This patch add an optimized strpbrk for POWER7 by using a different
algorithm than default implementation: it constructs a table based on
the 'accept' argument and use this table to check for any occurance on
the input string. The idea is similar as x86_64 uses.
For PowerPC some tunings were added, such as unroll loops and memory
clear using VSX instructions.
This patch add a optimized strcspn for POWER7 by using a different
algorithm than default implementation: it constructs a table based on
the 'accept' argument and use this table to check for any occurance
on the input string. The idea is similar as x86_64 uses.
For PowerPC some tunings were added, such as unroll loops and align
stack memory to table to 16 bytes (so VSX clean can ran without
alignment issues).
The optimization is achieved by following techniques:
> hashing of needle.
> hashing avoids scanning of duplicate entries in needle across the string.
> initializing the hash table with Vector instructions (VSX) by quadword access.
> unrolling when scanning for character in string across hash table.
The optimization is achieved by following techniques:
1. Doubleword aligned memory access and compares using
cmpb instruction.
2. Loop unrolling for byte load/store.
3. CPU pre-fetch to avoid cache miss.
This patch optimizes strrchr() for ppc64. It uses aligned memory
access along with cmpb instruction and CPU prefetch to avoid
cache misses for speed improvement.
