Josh Bleecher Snyder c9fd997524 cmd/compile: unroll comparisons to short constant strings ... 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>		2016-09-15 15:37:00 +00:00
..
bench	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
bugs	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
chan	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
ddd2.dir	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
dwarf
fixedbugs	cmd/compile: unwrap fewer CONVNOPs in staticassign	2016-09-15 14:08:10 +00:00
import2.dir	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
import4.dir
interface	cmd/compile: inline x, ok := y.(T) where T is a scalar	2016-08-17 01:12:01 +00:00
intrinsic.dir	cmd/compile: intrinsify Ctz, Bswap on ARM	2016-09-12 19:26:31 +00:00
ken	all: fix spelling mistakes	2016-04-03 17:03:15 +00:00
method4.dir
safe
stress	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
syntax	cmd/compile/internal/syntax: match old parser errors and line numbers	2016-08-19 01:10:21 +00:00
uintptrescapes.dir	cmd/compile, syscall: add //go:uintptrescapes comment, and use it	2016-07-06 20:48:41 +00:00
64bit.go
235.go
alg.go	test: add test that required algs get generated	2016-04-24 21:36:52 +00:00
alias1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
alias.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
append.go
args.go
assign1.go
assign.go
atomicload.go	cmd/compile: keep value use counts in SSA	2016-03-17 04:20:02 +00:00
bigalg.go
bigmap.go
blank1.go	cmd/compile: don't allow blank method declarations on builtins	2015-12-02 18:26:38 +00:00
blank.go
bom.go
bombad.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
bounds.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
chancap.go
chanlinear.go
char_lit1.go
char_lit.go
checkbce.go	cmd/compile: optimize integer "in range" expressions	2016-08-25 03:49:16 +00:00
clearfat.go
closedchan.go
closure1.go
closure2.go
closure.go
cmp6.go
cmp.go
cmplx.go
cmplxdivide1.go
cmplxdivide.c	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
cmplxdivide.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
complit1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
complit.go
compos.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
const1.go
const2.go
const3.go
const4.go
const5.go
const6.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
const.go
convert1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
convert3.go
convert.go
convlit1.go
convlit.go
convT2X.go
copy.go
crlf.go
ddd1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
ddd2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
ddd.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
decl.go
declbad.go
defer.go
deferfin.go
deferprint.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
deferprint.out
divide.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
divmod.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
empty.go
env.go
eof1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
eof.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
errchk	cmd/vet: make checking example names in _test packages more robust	2016-06-28 22:09:00 +00:00
escape2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape2n.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape3.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape4.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape5.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_array.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_because.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_calls.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_closure.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_field.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_iface.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_indir.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_level.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_map.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_param.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_slice.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_struct_param1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_struct_param2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape_struct_return.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
escape.go
fibo.go
finprofiled.go
float_lit2.go	test/float_lit2: fix expressions in comment	2016-09-14 16:39:47 +00:00
float_lit3.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
float_lit.go
floatcmp.go
for.go
func1.go
func2.go
func3.go
func4.go
func5.go
func6.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
func7.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
func8.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
func.go
funcdup2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
funcdup.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
gc1.go
gc2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
gc.go
gcstring.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
goprint.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
goprint.out
goto.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
heapsampling.go
helloworld.go
helloworld.out
if.go
import1.go
import2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
import4.go
import5.go
import.go
index0.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
index1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
index2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
index.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
indirect1.go
indirect.go
init1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
init.go
initcomma.go
initialize.go
initializerr.go
initloop.go
inline.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
int_lit.go
intcvt.go
intrinsic_atomic.go	cmd/compile: intrinsify Ctz, Bswap on ARM	2016-09-12 19:26:31 +00:00
intrinsic.go	cmd/compile: intrinsify Ctz, Bswap on ARM	2016-09-12 19:26:31 +00:00
iota.go
label1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
label.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
linkmain_run.go	test: fix linkmain test	2015-12-17 23:36:13 +00:00
linkmain.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
linkobj.go	cmd/compile: add -linkobj flag to allow writing object file in two parts	2016-05-09 17:31:45 +00:00
linkx_run.go	test: print output on link -X failure	2016-04-20 17:37:35 +00:00
linkx.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
literal.go
live1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
live2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
live_ssa.go	cmd/compile: add SSA backend for s390x and enable by default	2016-09-13 19:39:38 +00:00
live_syscall.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
live.go	cmd/compile: add SSA backend for s390x and enable by default	2016-09-13 19:39:38 +00:00
loopbce.go	cmd/compile: bce when max and limit are consts	2016-04-11 16:01:22 +00:00
mallocfin.go
map1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
map.go
maplinear.go
method1.go	cmd/compile: ignore receiver parameters in Eqtype	2016-03-17 00:38:15 +00:00
method2.go
method3.go
method4.go
method5.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
method.go
named1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
named.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
nil.go
nilcheck.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
nilptr2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
nilptr3_ssa.go	cmd/compile: redo nil checks	2016-09-15 02:42:13 +00:00
nilptr3.go	test: add test for CL 26831	2016-08-17 14:50:34 +00:00
nilptr4.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
nilptr.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
nosplit.go	cmd/compile: ppc64le working, not optimized enough	2016-08-18 16:34:47 +00:00
nul1.go	cmd/compile/internal/syntax: match old parser errors and line numbers	2016-08-19 01:10:21 +00:00
opt_branchlikely.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
parentype.go
peano.go
phiopt.go	test: re-enable phi optimization test	2016-09-13 20:06:13 +00:00
print.go
print.out
printbig.go
printbig.out
prove.go	cmd/compile: unroll comparisons to short constant strings	2016-09-15 15:37:00 +00:00
range.go
recover1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
recover2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
recover3.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
recover4.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
recover.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
reflectmethod1.go	cmd/compile: track reflect.Type.Method in deadcode	2016-03-11 21:19:20 +00:00
reflectmethod2.go	cmd/compile: track reflect.Type.Method in deadcode	2016-03-11 21:19:20 +00:00
reflectmethod3.go	cmd/compile: track reflect.Type.Method in deadcode	2016-03-11 21:19:20 +00:00
reflectmethod4.go	cmd/link: treat reflect.Value.Method like Call	2016-03-11 22:07:02 +00:00
rename1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
rename.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
reorder2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
reorder.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
return.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
rotate0.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
rotate1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
rotate2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
rotate3.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
rotate.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
run.go	test: remove unused variable	2016-08-16 21:46:54 +00:00
rune.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
runtime.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
shift1.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
shift2.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
sieve.go
sigchld.go
sigchld.out
simassign.go
sinit_run.go
sinit.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
sizeof.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
slice3.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
slice3err.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
slicecap.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
sliceopt.go	cmd/compile: add SSA backend for s390x and enable by default	2016-09-13 19:39:38 +00:00
solitaire.go
stack.go
strength.go	cmd/compile: generalize strength reduction of mulq	2016-03-30 22:27:13 +00:00
string_lit.go
stringrange.go
struct0.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
switch2.go	cmd/compile/internal/syntax: match old parser errors and line numbers	2016-08-19 01:10:21 +00:00
switch3.go
switch4.go
switch5.go	cmd/compile: use a map to track const switch cases	2016-08-23 05:28:33 +00:00
switch6.go	cmd/compile: set correct line number for multiple defaults in switch error	2016-08-22 19:56:06 +00:00
switch.go
tinyfin.go
torture.go
turing.go
typecheck.go
typecheckloop.go
typeswitch1.go
typeswitch2.go
typeswitch3.go
typeswitch.go
uintptrescapes2.go	cmd/compile, syscall: add //go:uintptrescapes comment, and use it	2016-07-06 20:48:41 +00:00
uintptrescapes.go	cmd/compile, syscall: add //go:uintptrescapes comment, and use it	2016-07-06 20:48:41 +00:00
undef.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
utf.go
varerr.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
varinit.go
writebarrier.go	all: make copyright headers consistent with one space after period	2016-05-02 13:43:18 +00:00
zerodivide.go