1e5bb416d8
This CL implements Mul64uhilo, Hmul64, Hmul64u, and Avg64u
on 32-bit systems, with the effect that constant division of both
int64s and uint64s can now be emitted directly in all cases,
and also that bits.Mul64 can be intrinsified on 32-bit systems.
Previously, constant division of uint64s by values 0 ≤ c ≤ 0xFFFF were
implemented as uint32 divisions by c and some fixup. After expanding
those smaller constant divisions, the code for i/999 required:
(386) 7 mul, 10 add, 2 sub, 3 rotate, 3 shift (104 bytes)
(arm) 7 mul, 9 add, 3 sub, 2 shift (104 bytes)
(mips) 7 mul, 10 add, 5 sub, 6 shift, 3 sgtu (176 bytes)
For that much code, we might as well use a full 64x64->128 multiply
that can be used for all divisors, not just small ones.
Having done that, the same i/999 now generates:
(386) 4 mul, 9 add, 2 sub, 2 or, 6 shift (112 bytes)
(arm) 4 mul, 8 add, 2 sub, 2 or, 3 shift (92 bytes)
(mips) 4 mul, 11 add, 3 sub, 6 shift, 8 sgtu, 4 or (196 bytes)
The size increase on 386 is due to a few extra register spills.
The size increase on mips is due to add-with-carry being hard.
The new approach is more general, letting us delete the old special case
and guarantee that all int64 and uint64 divisions by constants are
generated directly on 32-bit systems.
This especially speeds up code making heavy use of bits.Mul64 with
a constant argument, which happens in strconv and various crypto
packages. A few examples are benchmarked below.
pkg: cmd/compile/internal/test
benchmark \ host local linux-amd64 s7 linux-386 s7:GOARCH=386
vs base vs base vs base vs base vs base
DivconstI64 ~ ~ ~ -49.66% -21.02%
ModconstI64 ~ ~ ~ -13.45% +14.52%
DivisiblePow2constI64 ~ ~ ~ +0.97% -1.32%
DivisibleconstI64 ~ ~ ~ -20.01% -48.28%
DivisibleWDivconstI64 ~ ~ -1.76% -38.59% -42.74%
DivconstU64/3 ~ ~ ~ -13.82% -4.09%
DivconstU64/5 ~ ~ ~ -14.10% -3.54%
DivconstU64/37 -2.07% -4.45% ~ -19.60% -9.55%
DivconstU64/1234567 ~ ~ ~ -61.55% -56.93%
ModconstU64 ~ ~ ~ -6.25% ~
DivisibleconstU64 ~ ~ ~ -2.78% -7.82%
DivisibleWDivconstU64 ~ ~ ~ +4.23% +2.56%
pkg: math/bits
benchmark \ host s7 linux-amd64 linux-386 s7:GOARCH=386
vs base vs base vs base vs base
Add ~ ~ ~ ~
Add32 +1.59% ~ ~ ~
Add64 ~ ~ ~ ~
Add64multiple ~ ~ ~ ~
Sub ~ ~ ~ ~
Sub32 ~ ~ ~ ~
Sub64 ~ ~ -9.20% ~
Sub64multiple ~ ~ ~ ~
Mul ~ ~ ~ ~
Mul32 ~ ~ ~ ~
Mul64 ~ ~ -41.58% -53.21%
Div ~ ~ ~ ~
Div32 ~ ~ ~ ~
Div64 ~ ~ ~ ~
pkg: strconv
benchmark \ host s7 linux-amd64 linux-386 s7:GOARCH=386
vs base vs base vs base vs base
ParseInt/Pos/7bit ~ ~ -11.08% -6.75%
ParseInt/Pos/26bit ~ ~ -13.65% -11.02%
ParseInt/Pos/31bit ~ ~ -14.65% -9.71%
ParseInt/Pos/56bit -1.80% ~ -17.97% -10.78%
ParseInt/Pos/63bit ~ ~ -13.85% -9.63%
ParseInt/Neg/7bit ~ ~ -12.14% -7.26%
ParseInt/Neg/26bit ~ ~ -14.18% -9.81%
ParseInt/Neg/31bit ~ ~ -14.51% -9.02%
ParseInt/Neg/56bit ~ ~ -15.79% -9.79%
ParseInt/Neg/63bit ~ ~ -15.68% -11.07%
AppendFloat/Decimal ~ ~ -7.25% -12.26%
AppendFloat/Float ~ ~ -15.96% -19.45%
AppendFloat/Exp ~ ~ -13.96% -17.76%
AppendFloat/NegExp ~ ~ -14.89% -20.27%
AppendFloat/LongExp ~ ~ -12.68% -17.97%
AppendFloat/Big ~ ~ -11.10% -16.64%
AppendFloat/BinaryExp ~ ~ ~ ~
AppendFloat/32Integer ~ ~ -10.05% -10.91%
AppendFloat/32ExactFraction ~ ~ -8.93% -13.00%
AppendFloat/32Point ~ ~ -10.36% -14.89%
AppendFloat/32Exp ~ ~ -9.88% -13.54%
AppendFloat/32NegExp ~ ~ -10.16% -14.26%
AppendFloat/32Shortest ~ ~ -11.39% -14.96%
AppendFloat/32Fixed8Hard ~ ~ ~ -2.31%
AppendFloat/32Fixed9Hard ~ ~ ~ -7.01%
AppendFloat/64Fixed1 ~ ~ -2.83% -8.23%
AppendFloat/64Fixed2 ~ ~ ~ -7.94%
AppendFloat/64Fixed3 ~ ~ -4.07% -7.22%
AppendFloat/64Fixed4 ~ ~ -7.24% -7.62%
AppendFloat/64Fixed12 ~ ~ -6.57% -4.82%
AppendFloat/64Fixed16 ~ ~ -4.00% -5.81%
AppendFloat/64Fixed12Hard -2.22% ~ -4.07% -6.35%
AppendFloat/64Fixed17Hard -2.12% ~ ~ -3.79%
AppendFloat/64Fixed18Hard -1.89% ~ +2.48% ~
AppendFloat/Slowpath64 -1.85% ~ -14.49% -18.21%
AppendFloat/SlowpathDenormal64 ~ ~ -13.08% -19.41%
pkg: crypto/internal/fips140/nistec/fiat
benchmark \ host s7 linux-amd64 linux-386 s7:GOARCH=386
vs base vs base vs base vs base
Mul/P224 ~ ~ -29.95% -39.60%
Mul/P384 ~ ~ -37.11% -63.33%
Mul/P521 ~ ~ -26.62% -12.42%
Square/P224 +1.46% ~ -40.62% -49.18%
Square/P384 ~ ~ -45.51% -69.68%
Square/P521 +90.37% ~ -25.26% -11.23%
(The +90% is a separate problem and not real; that much variation
can be seen on that system by running the same binary from two
different files.)
pkg: crypto/internal/fips140/edwards25519
benchmark \ host s7 linux-amd64 linux-386 s7:GOARCH=386
vs base vs base vs base vs base
EncodingDecoding ~ ~ -34.67% -35.75%
ScalarBaseMult ~ ~ -31.25% -30.29%
ScalarMult ~ ~ -33.45% -32.54%
VarTimeDoubleScalarBaseMult ~ ~ -33.78% -33.68%
Change-Id: Id3c91d42cd01def6731b755e99f8f40c6ad1bb65
Reviewed-on: https://go-review.googlesource.com/c/go/+/716061
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
The test directory contains tests of the Go tool chain and runtime. It includes black box tests, regression tests, and error output tests. They are run as part of all.bash.
To run just these tests, execute:
../bin/go test cmd/internal/testdir
To run just tests from specified files in this directory, execute:
../bin/go test cmd/internal/testdir -run='Test/(file1.go|file2.go|...)'
Standard library tests should be written as regular Go tests in the appropriate package.
The tool chain and runtime also have regular Go tests in their packages. The main reasons to add a new test to this directory are:
- it is most naturally expressed using the test runner; or
- it is also applicable to
gccgoand other Go tool chains.