The encoding/binary little- and big-endian load and store routines are
frequently used in performance sensitive code. They look fairly complex
to the inliner. Though the routines themselves can be inlined,
code using them typically cannot be.
Yet they typically compile down to an instruction or two
on architectures that support merging such loads.
This change teaches the inliner to treat calls to these methods as cheap,
so that code using them will be more inlineable.
It'd be better to teach the inliner that this pattern of code is cheap,
rather than these particular methods. However, that is difficult to do
robustly when working with the IR representation. And the broader project
of which that would be a part, namely to model the rest of the compiler
in the inliner, is probably a non-starter. By way of contrast, imperfect
though it is, this change is an easy, cheap, and useful heuristic.
If/when we base inlining decisions on more accurate information obtained
later in the compilation process, or on PGO/FGO, we can remove this
and other such heuristics.
Newly inlineable functions in the standard library:
crypto/cipher.gcmInc32
crypto/sha512.appendUint64
crypto/md5.appendUint64
crypto/sha1.appendUint64
crypto/sha256.appendUint64
vendor/golang.org/x/crypto/poly1305.initialize
encoding/gob.(*encoderState).encodeUint
vendor/golang.org/x/text/unicode/norm.buildRecompMap
net/http.(*http2SettingsFrame).Setting
net/http.http2parseGoAwayFrame
net/http.http2parseWindowUpdateFrame
Benchmark impact for encoding/gob (the only package I measured):
name old time/op new time/op delta
EndToEndPipe-8 2.25µs ± 1% 2.21µs ± 3% -1.79% (p=0.000 n=28+27)
EndToEndByteBuffer-8 93.3ns ± 5% 94.2ns ± 5% ~ (p=0.174 n=30+30)
EndToEndSliceByteBuffer-8 10.5µs ± 1% 10.6µs ± 1% +0.87% (p=0.000 n=30+30)
EncodeComplex128Slice-8 1.81µs ± 0% 1.75µs ± 1% -3.23% (p=0.000 n=28+30)
EncodeFloat64Slice-8 900ns ± 1% 847ns ± 0% -5.91% (p=0.000 n=29+28)
EncodeInt32Slice-8 1.02µs ± 0% 0.90µs ± 0% -11.82% (p=0.000 n=28+26)
EncodeStringSlice-8 1.16µs ± 1% 1.04µs ± 1% -10.20% (p=0.000 n=29+26)
EncodeInterfaceSlice-8 28.7µs ± 3% 29.2µs ± 6% ~ (p=0.067 n=29+30)
DecodeComplex128Slice-8 7.98µs ± 1% 7.96µs ± 1% -0.27% (p=0.017 n=30+30)
DecodeFloat64Slice-8 4.33µs ± 1% 4.34µs ± 1% +0.24% (p=0.022 n=30+29)
DecodeInt32Slice-8 4.18µs ± 1% 4.18µs ± 0% ~ (p=0.074 n=30+28)
DecodeStringSlice-8 13.2µs ± 1% 13.1µs ± 1% -0.64% (p=0.000 n=28+28)
DecodeStringsSlice-8 31.9µs ± 1% 31.8µs ± 1% -0.34% (p=0.001 n=30+30)
DecodeBytesSlice-8 8.88µs ± 1% 8.84µs ± 1% -0.48% (p=0.000 n=30+30)
DecodeInterfaceSlice-8 64.1µs ± 1% 64.2µs ± 1% ~ (p=0.173 n=30+28)
DecodeMap-8 74.3µs ± 0% 74.2µs ± 0% ~ (p=0.131 n=29+30)
Fixes#42958
Change-Id: Ie048b8976fb403d8bcc72ac6bde4b33e133e2a47
Reviewed-on: https://go-review.googlesource.com/c/go/+/349931
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
