tree 012b3e9dd9f705c17202cce50a1f5e91bb96b8e1
parent 8eb36ae9c76d3111afa1bee19b18c0f6cfcfe982
author Lynn Boger <laboger@linux.vnet.ibm.com> 1534368846 -0400
committer Lynn Boger <laboger@linux.vnet.ibm.com> 1536863093 +0000

cmd/compile: improve rules for PPC64.rules

This adds some improvements to the rules for PPC64 to eliminate
unnecessary zero or sign extends, and fix some rule for truncates
which were not always using the correct sign instruction.

This reduces of size of many functions by 1 or 2 instructions and
can improve performance in cases where the execution time depends
on small loops where at least 1 instruction was removed and where that
loop contributes a significant amount of the total execution time.

Included is a testcase for codegen to verify the sign/zero extend
instructions are omitted.

An example of the improvement (strings):
IndexAnyASCII/256:1-16     392ns ± 0%   369ns ± 0%  -5.79%  (p=0.000 n=1+10)
IndexAnyASCII/256:2-16     397ns ± 0%   376ns ± 0%  -5.23%  (p=0.000 n=1+9)
IndexAnyASCII/256:4-16     405ns ± 0%   384ns ± 0%  -5.19%  (p=1.714 n=1+6)
IndexAnyASCII/256:8-16     427ns ± 0%   403ns ± 0%  -5.57%  (p=0.000 n=1+10)
IndexAnyASCII/256:16-16    441ns ± 0%   418ns ± 1%  -5.33%  (p=0.000 n=1+10)
IndexAnyASCII/4096:1-16   5.62µs ± 0%  5.27µs ± 1%  -6.31%  (p=0.000 n=1+10)
IndexAnyASCII/4096:2-16   5.67µs ± 0%  5.29µs ± 0%  -6.67%  (p=0.222 n=1+8)
IndexAnyASCII/4096:4-16   5.66µs ± 0%  5.28µs ± 1%  -6.66%  (p=0.000 n=1+10)
IndexAnyASCII/4096:8-16   5.66µs ± 0%  5.31µs ± 1%  -6.10%  (p=0.000 n=1+10)
IndexAnyASCII/4096:16-16  5.70µs ± 0%  5.33µs ± 1%  -6.43%  (p=0.182 n=1+10)

Change-Id: I739a6132b505936d39001aada5a978ff2a5f0500
Reviewed-on: https://go-review.googlesource.com/129875
Reviewed-by: David Chase <drchase@google.com>