cmd/compile: intrinsify RotateLeft32 on wasm

wasm has 32-bit versions of all integer operations. This change
lowers RotateLeft32 to i32.rotl on wasm and intrinsifies the math/bits
call.  Benchmarking on amd64 under node.js this is ~25% faster.

node v10.15.3/amd64
name          old time/op  new time/op  delta
RotateLeft    8.37ns ± 1%  8.28ns ± 0%   -1.05%  (p=0.029 n=4+4)
RotateLeft8   11.9ns ± 1%  11.8ns ± 0%     ~     (p=0.167 n=5+5)
RotateLeft16  11.8ns ± 0%  11.8ns ± 0%     ~     (all equal)
RotateLeft32  11.9ns ± 1%   8.7ns ± 0%  -26.32%  (p=0.008 n=5+5)
RotateLeft64  8.31ns ± 1%  8.43ns ± 2%     ~     (p=0.063 n=5+5)

Updates #31265

Change-Id: I5b8e155978faeea536c4f6427ac9564d2f096a46
Reviewed-on: https://go-review.googlesource.com/c/go/+/182359
Run-TryBot: Brian Kessler <brian.m.kessler@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Richard Musiol <neelance@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go
index 61e5db56e1..9cdfe0b06a 100644
--- a/test/codegen/mathbits.go
+++ b/test/codegen/mathbits.go
@@ -213,6 +213,7 @@ func RotateLeft32(n uint32) uint32 {
 	// ppc64:"ROTLW"
 	// ppc64le:"ROTLW"
 	// s390x:"RLL"
+	// wasm:"I32Rotl"
 	return bits.RotateLeft32(n, 9)
 }
 
@@ -232,6 +233,7 @@ func RotateLeftVariable(n uint, m int) uint {
 	// ppc64:"ROTL"
 	// ppc64le:"ROTL"
 	// s390x:"RLLG"
+	// wasm:"I64Rotl"
 	return bits.RotateLeft(n, m)
 }
 
@@ -241,6 +243,7 @@ func RotateLeftVariable64(n uint64, m int) uint64 {
 	// ppc64:"ROTL"
 	// ppc64le:"ROTL"
 	// s390x:"RLLG"
+	// wasm:"I64Rotl"
 	return bits.RotateLeft64(n, m)
 }
 
@@ -251,6 +254,7 @@ func RotateLeftVariable32(n uint32, m int) uint32 {
 	// ppc64:"ROTLW"
 	// ppc64le:"ROTLW"
 	// s390x:"RLL"
+	// wasm:"I32Rotl"
 	return bits.RotateLeft32(n, m)
 }