cmd/compile: improve lowered moves and zeros for ppc64le

This change includes the following:
- Generate LXV/STXV sequences instead of LXVD2X/STXVD2X on power9.
These instructions do not require an index register, which
allows more loads and stores within a loop without initializing
multiple index registers. The LoweredQuadXXX generate LXV/STXV.
- Create LoweredMoveXXXShort and LoweredZeroXXXShort for short
moves that don't generate loops, and therefore don't clobber the
address registers or flags.
- Use registers other than R3 and R4 to avoid conflicting with
registers that have already been allocated to avoid unnecessary
register moves.
- Eliminate the use of R14 as scratch register and use R31
instead.
- Add PCALIGN when the LoweredMoveXXX or LoweredZeroXXX generates a
loop with more than 3 iterations.

This performance opportunity was noticed in github.com/golang/snappy
benchmarks. Results on power9:

WordsDecode1e1    54.1ns ± 0%    53.8ns ± 0%   -0.51%  (p=0.029 n=4+4)
WordsDecode1e2     287ns ± 0%     282ns ± 1%   -1.83%  (p=0.029 n=4+4)
WordsDecode1e3    3.98µs ± 0%    3.64µs ± 0%   -8.52%  (p=0.029 n=4+4)
WordsDecode1e4    66.9µs ± 0%    67.0µs ± 0%   +0.20%  (p=0.029 n=4+4)
WordsDecode1e5     723µs ± 0%     723µs ± 0%   -0.01%  (p=0.200 n=4+4)
WordsDecode1e6    7.21ms ± 0%    7.21ms ± 0%   -0.02%  (p=1.000 n=4+4)
WordsEncode1e1    29.9ns ± 0%    29.4ns ± 0%   -1.51%  (p=0.029 n=4+4)
WordsEncode1e2    2.12µs ± 0%    1.75µs ± 0%  -17.70%  (p=0.029 n=4+4)
WordsEncode1e3    11.7µs ± 0%    11.2µs ± 0%   -4.61%  (p=0.029 n=4+4)
WordsEncode1e4     119µs ± 0%     120µs ± 0%   +0.36%  (p=0.029 n=4+4)
WordsEncode1e5    1.21ms ± 0%    1.22ms ± 0%   +0.41%  (p=0.029 n=4+4)
WordsEncode1e6    12.0ms ± 0%    12.0ms ± 0%   +0.57%  (p=0.029 n=4+4)
RandomEncode       286µs ± 0%     203µs ± 0%  -28.82%  (p=0.029 n=4+4)
ExtendMatch       47.4µs ± 0%    47.0µs ± 0%   -0.85%  (p=0.029 n=4+4)

Change-Id: Iecad3a39ae55280286e42760a5c9d5c1168f5858
Reviewed-on: https://go-review.googlesource.com/c/go/+/226539
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/test/codegen/copy.go b/test/codegen/copy.go
index 46c2bde9ab..db75cde1c6 100644
--- a/test/codegen/copy.go
+++ b/test/codegen/copy.go
@@ -34,6 +34,8 @@ func movesmall7() {
 func movesmall16() {
 	x := [...]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
 	// amd64:-".*memmove"
+	// ppc64:".*memmove"
+	// ppc64le:".*memmove"
 	copy(x[1:], x[:])
 }
 
@@ -41,10 +43,34 @@ var x [256]byte
 
 // Check that large disjoint copies are replaced with moves.
 
+func moveDisjointStack32() {
+        var s [32]byte
+        // ppc64:-".*memmove"
+        // ppc64le:-".*memmove"
+        // ppc64le/power8:"LXVD2X",-"ADD",-"BC"
+        // ppc64le/power9:"LXV",-"LXVD2X",-"ADD",-"BC"
+        copy(s[:], x[:32])
+        runtime.KeepAlive(&s)
+}
+
+func moveDisjointStack64() {
+        var s [96]byte
+        // ppc64:-".*memmove"
+        // ppc64le:-".*memmove"
+        // ppc64le/power8:"LXVD2X","ADD","BC"
+        // ppc64le/power9:"LXV",-"LXVD2X",-"ADD",-"BC"
+        copy(s[:], x[:96])
+        runtime.KeepAlive(&s)
+}
+
 func moveDisjointStack() {
 	var s [256]byte
 	// s390x:-".*memmove"
 	// amd64:-".*memmove"
+	// ppc64:-".*memmove"
+	// ppc64le:-".*memmove"
+	// ppc64le/power8:"LXVD2X"
+	// ppc64le/power9:"LXV",-"LXVD2X"
 	copy(s[:], x[:])
 	runtime.KeepAlive(&s)
 }
@@ -53,6 +79,10 @@ func moveDisjointArg(b *[256]byte) {
 	var s [256]byte
 	// s390x:-".*memmove"
 	// amd64:-".*memmove"
+	// ppc64:-".*memmove"
+	// ppc64le:-".*memmove"
+	// ppc64le/power8:"LXVD2X"
+	// ppc64le/power9:"LXV",-"LXVD2X"
 	copy(s[:], b[:])
 	runtime.KeepAlive(&s)
 }
@@ -60,6 +90,10 @@ func moveDisjointArg(b *[256]byte) {
 func moveDisjointNoOverlap(a *[256]byte) {
 	// s390x:-".*memmove"
 	// amd64:-".*memmove"
+	// ppc64:-".*memmove"
+	// ppc64le:-".*memmove"
+	// ppc64le/power8:"LXVD2X"
+	// ppc64le/power9:"LXV",-"LXVD2X"
 	copy(a[:], a[128:])
 }