Unroll s == "ab" to
len(s) == 2 && s[0] == 'a' && s[1] == 'b'
This generates faster and shorter code
by avoiding a runtime call.
Do something similar for !=.
The cutoff length is 6. This was chosen empirically
by examining binary sizes on arm, arm64, 386, and amd64
using the SSA backend.
For all architectures examined, 4, 5, and 6 were
the ideal cutoff, with identical binary sizes.
The distribution of constant string equality sizes
during 'go build -a std' is:
40.81% 622 len 0
14.11% 215 len 4
9.45% 144 len 1
7.81% 119 len 3
7.48% 114 len 5
5.12% 78 len 7
4.13% 63 len 2
3.54% 54 len 8
2.69% 41 len 6
1.18% 18 len 10
0.85% 13 len 9
0.66% 10 len 14
0.59% 9 len 17
0.46% 7 len 11
0.26% 4 len 12
0.20% 3 len 19
0.13% 2 len 13
0.13% 2 len 15
0.13% 2 len 16
0.07% 1 len 20
0.07% 1 len 23
0.07% 1 len 33
0.07% 1 len 36
A cutoff of length 6 covers most of the cases.
Benchmarks on amd64 comparing a string to a constant of length 3:
Cmp/1same-8 4.78ns ± 6% 0.94ns ± 9% -80.26% (p=0.000 n=20+20)
Cmp/1diffbytes-8 6.43ns ± 6% 0.96ns ±11% -85.13% (p=0.000 n=20+20)
Cmp/3same-8 4.71ns ± 5% 1.28ns ± 5% -72.90% (p=0.000 n=20+20)
Cmp/3difffirstbyte-8 6.33ns ± 7% 1.27ns ± 7% -79.90% (p=0.000 n=20+20)
Cmp/3difflastbyte-8 6.34ns ± 8% 1.26ns ± 9% -80.13% (p=0.000 n=20+20)
The change to the prove test preserves the
existing intent of the test. When the string was
short, there was a new "proved in bounds" report
that referred to individual byte comparisons.
Change-Id: I593ac303b0d11f275672090c5c786ea0c6b8da13
Reviewed-on: https://go-review.googlesource.com/26758
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
func f(a, b bool) bool {
return a || b
}
is now a single instructions (excluding loading and unloading the arguments):
v10 = ORB <bool> v11 v12 : AX
Change-Id: Iff63399410cb46909f4318ea1c3f45a029f4aa5e
Reviewed-on: https://go-review.googlesource.com/21872
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Handle this case:
if 0 <= i && i < len(a) {
use a[i]
}
Shaves about 5k from pkg/tools/linux_amd64/*.
Change-Id: I6675ff49aa306b0d241b074c5738e448204cd981
Reviewed-on: https://go-review.googlesource.com/21431
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
There are 5293 loop in the main go repository.
A survey of the top most common for loops:
18 for __k__ := 0; i < len(sa.Addr); i++ {
19 for __k__ := 0; ; i++ {
19 for __k__ := 0; i < 16; i++ {
25 for __k__ := 0; i < length; i++ {
30 for __k__ := 0; i < 8; i++ {
49 for __k__ := 0; i < len(s); i++ {
67 for __k__ := 0; i < n; i++ {
376 for __k__ := range __slice__ {
685 for __k__, __v__ := range __slice__ {
2074 for __, __v__ := range __slice__ {
The algorithm to find induction variables handles all cases
with an upper limit. It currently doesn't find related induction
variables such as c * ind or c + ind.
842 out of 22954 bound checks are removed for src/make.bash.
1957 out of 42952 bounds checks are removed for src/all.bash.
Things to do in follow-up CLs:
* Find the associated pointer for `for _, v := range a {}`
* Drop the NilChecks on the pointer.
* Replace the implicit induction variable by a loop over the pointer
Generated garbage can be reduced if we share the sdom between passes.
% benchstat old.txt new.txt
name old time/op new time/op delta
Template 337ms ± 3% 333ms ± 3% ~ (p=0.258 n=9+9)
GoTypes 1.11s ± 2% 1.10s ± 2% ~ (p=0.912 n=10+10)
Compiler 5.25s ± 1% 5.29s ± 2% ~ (p=0.077 n=9+9)
MakeBash 33.5s ± 1% 34.1s ± 2% +1.85% (p=0.011 n=9+9)
name old alloc/op new alloc/op delta
Template 63.6MB ± 0% 63.9MB ± 0% +0.52% (p=0.000 n=10+9)
GoTypes 218MB ± 0% 219MB ± 0% +0.59% (p=0.000 n=10+9)
Compiler 978MB ± 0% 985MB ± 0% +0.69% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
Template 582k ± 0% 583k ± 0% +0.10% (p=0.000 n=10+10)
GoTypes 1.78M ± 0% 1.78M ± 0% +0.12% (p=0.000 n=10+10)
Compiler 7.68M ± 0% 7.69M ± 0% +0.05% (p=0.000 n=10+10)
name old text-bytes new text-bytes delta
HelloSize 581k ± 0% 581k ± 0% -0.08% (p=0.000 n=10+10)
CmdGoSize 6.40M ± 0% 6.39M ± 0% -0.08% (p=0.000 n=10+10)
name old data-bytes new data-bytes delta
HelloSize 3.66k ± 0% 3.66k ± 0% ~ (all samples are equal)
CmdGoSize 134k ± 0% 134k ± 0% ~ (all samples are equal)
name old bss-bytes new bss-bytes delta
HelloSize 126k ± 0% 126k ± 0% ~ (all samples are equal)
CmdGoSize 149k ± 0% 149k ± 0% ~ (all samples are equal)
name old exe-bytes new exe-bytes delta
HelloSize 947k ± 0% 946k ± 0% -0.01% (p=0.000 n=10+10)
CmdGoSize 9.92M ± 0% 9.91M ± 0% -0.06% (p=0.000 n=10+10)
Change-Id: Ie74bdff46fd602db41bb457333d3a762a0c3dc4d
Reviewed-on: https://go-review.googlesource.com/20517
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
Find comparisons to constants and propagate that information
down the dominator tree. Use it to resolve other constant
comparisons on the same variable.
So if we know x >= 7, then a x > 4 condition must return true.
This change allows us to use "_ = b[7]" hints to eliminate bounds checks.
Fixes#14900
Change-Id: Idbf230bd5b7da43de3ecb48706e21cf01bf812f7
Reviewed-on: https://go-review.googlesource.com/21008
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
* Refacts a bit saving and restoring parents restrictions
* Shaves ~100k from pkg/tools/linux_amd64,
but most of the savings come from the rewrite rules.
* Improves on the following artificial test case:
func f1(a4 bool, a6 bool) bool {
return a6 || (a6 || (a6 || a4)) || (a6 || (a4 || a6 || (false || a6)))
}
Change-Id: I714000f75a37a3a6617c6e6834c75bd23674215f
Reviewed-on: https://go-review.googlesource.com/20306
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
* It does very simple bounds checking elimination. E.g.
removes the second check in for i := range a { a[i]++; a[i++]; }
* Improves on the following redundant expression:
return a6 || (a6 || (a6 || a4)) || (a6 || (a4 || a6 || (false || a6)))
* Linear in the number of block edges.
I patched in CL 12960 that does bounds, nil and constant propagation
to make sure this CL is not just redundant. Size of pkg/tool/linux_amd64/*
(excluding compile which is affected by this change):
With IsInBounds and IsSliceInBounds
-this -12960 92285080
+this -12960 91947416
-this +12960 91978976
+this +12960 91923088
Gain is ~110% of 12960.
Without IsInBounds and IsSliceInBounds (older run)
-this -12960 95515512
+this -12960 95492536
-this +12960 95216920
+this +12960 95204440
Shaves 22k on its own.
* Can we handle IsInBounds better with this? In
for i := range a { a[i]++; } the bounds checking at a[i]
is not eliminated.
Change-Id: I98957427399145fb33693173fd4d5a8d71c7cc20
Reviewed-on: https://go-review.googlesource.com/19710
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
