delta/go-git.git/src/math, branch dev.go2go

cmd/compile: optimize single-precision floating point square root

2021-03-02T06:38:07+00:00

Add generic rule to rewrite the single-precision square root expression
with one single-precision instruction. The optimization will reduce two
times of precision converting between double-precision and single-precision.

On arm64 flatform.

previous:
  FCVTSD F0, F0
  FSQRTD F0, F0
  FCVTDS F0, F0

optimized:
  FSQRTS S0, S0

And this patch adds the test case to check the correctness.

This patch refers to CL 241877, contributed by Alice Xu
(dianhong.xu@arm.com)

Change-Id: I6de5d02281c693017ac4bd4c10963dd55989bd7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/276873
Trust: fannie zhang 
Run-TryBot: fannie zhang 
TryBot-Result: Go Bot 
Reviewed-by: Keith Randall

all: go fmt std cmd (but revert vendor)

2021-02-20T03:54:50+00:00

Make all our package sources use Go 1.17 gofmt format
(adding //go:build lines).

Part of //go:build change (#41184).
See https://golang.org/design/draft-gobuild

Change-Id: Ia0534360e4957e58cd9a18429c39d0e32a6addb4
Reviewed-on: https://go-review.googlesource.com/c/go/+/294430
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Jason A. Donenfeld 
Reviewed-by: Ian Lance Taylor

math: remove most 387 implementations

2021-02-19T00:41:09+00:00

The Surface Pro X's 386 simulator is not completely faithful to a real 387.
The most egregious problem is that it computes Log2(8) as 2.9999999999999996,
but it has some other subtler problems as well. All the problems occur in
routines that we don't even bother with assembly for on amd64.
If the speed of Go code is OK on amd64 it should be OK on 386 too.
Just remove all the 386-only assembly functions.

This leaves Ceil, Floor, Trunc, Hypot, and Sqrt in 386 assembly,
all of which are also in assembly on amd64 and all of which pass
their tests on Surface Pro X.

Compared to amd64, the 386 port omits assembly for Min, Max, and Log.
It never had Min and Max, and this CL deletes Log because Log2 wasn't
even correct. (None of the other architectures have assembly Log either.)

Change-Id: I5eb6c61084467035269d4098a36001447b7a0601
Reviewed-on: https://go-review.googlesource.com/c/go/+/291229
Trust: Russ Cox 
Reviewed-by: Cherry Zhang 
Reviewed-by: Brad Fitzpatrick

math/big: fix comment in divRecursiveStep

2021-02-03T15:04:02+00:00

There appears to be a typo in the description of
the recursive division algorithm.

Two things seem suspicious with the original comment:
  1. It is talking about choosing s, but s doesn't
     appear anywhere in the equation.
  2. The math in the equation is incorrect.

Where
  B = len(v)/2
  s = B - 1

Proof that it is incorrect:
    len(v) - B >= B + 1
    len(v) - len(v)/2 >= len(v)/2 + 1

    This doesn't hold if len(v) is even, e.g. 10:
    10 - 10/2 >= 10/2 + 1
    10 - 5 >= 5 + 1
    5 >= 6  // this is false

The new equation will be the following,
which will be mathematically correct:
    len(v) - s >= B + 1
    len(v) - (len(v)/2 - 1) >= len(v)/2 + 1
    len(v) - len(v)/2 + 1 >= len(v)/2 + 1
    len(v) - len(v)/2 >= len(v)/2

    This holds if len(v) is even or odd.

    e.g. 10
    10 - 10/2 >= 10/2
    10 - 5 >= 5
    5 >= 5

    e.g. 11
    11 - 11/2 >= 11/2
    11 - 5 >= 5
    6 >= 5

Change-Id: If77ce09286cf7038637b5dfd0fb7d4f828023f56
Reviewed-on: https://go-review.googlesource.com/c/go/+/287372
Run-TryBot: Katie Hockman 
Reviewed-by: Filippo Valsorda 
Trust: Katie Hockman

math: fix typo in sqrt.go code comment

2021-01-27T00:15:06+00:00

"it does not necessary" -> "it is not necessary"

Change-Id: I66f9cf2670d76b3686badb4a537b3ec084447d62
GitHub-Last-Rev: 52a0f9993abf25369cdb6b31eaf476df1626cf87
GitHub-Pull-Request: golang/go#43935
Reviewed-on: https://go-review.googlesource.com/c/go/+/287052
Reviewed-by: Robert Griesemer 
Reviewed-by: Ian Lance Taylor 
Trust: Robert Griesemer

math/rand: fix typo in comment

2021-01-04T17:59:30+00:00

Change-Id: I57fbabf272bdfd61918db155ee6f7091f18e5979
GitHub-Last-Rev: e138804b1ab8086b3742861873b077d6cca8108a
GitHub-Pull-Request: golang/go#43495
Reviewed-on: https://go-review.googlesource.com/c/go/+/281373
Reviewed-by: Ian Lance Taylor 
Trust: Alberto Donizetti

math/big: add test for recursive division panic

2020-12-14T20:56:03+00:00

The vulnerability that allowed this panic is
CVE-2020-28362 and has been fixed in a security
release, per #42552.

Change-Id: I774bcda2cc83cdd5a273d21c8d9f4b53fa17c88f
Reviewed-on: https://go-review.googlesource.com/c/go/+/277959
Run-TryBot: Katie Hockman 
TryBot-Result: Go Bot 
Trust: Katie Hockman 
Reviewed-by: Filippo Valsorda

all: update to use os.ReadFile, os.WriteFile, os.CreateTemp, os.MkdirTemp

2020-12-09T19:12:23+00:00

As part of #42026, these helpers from io/ioutil were moved to os.
(ioutil.TempFile and TempDir became os.CreateTemp and MkdirTemp.)

Update the Go tree to use the preferred names.

As usual, code compiled with the Go 1.4 bootstrap toolchain
and code vendored from other sources is excluded.

ReadDir changes are in a separate CL, because they are not a
simple search and replace.

For #42026.

Change-Id: If318df0216d57e95ea0c4093b89f65e5b0ababb3
Reviewed-on: https://go-review.googlesource.com/c/go/+/266365
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Ian Lance Taylor

math/big: remove the s390x assembly for shlVU and shrVU

2020-12-03T18:43:06+00:00

The s390x assembly for shlVU does a forward copy when the shift amount s
is 0. This causes corruption of the result z when z is aliased to the
input x.

This fix removes the s390x assembly for both shlVU and shrVU so the pure
go implementations will be used.

Test cases have been added to the existing TestShiftOverlap test to
cover shift values of 0, 1 and (_W - 1).

Fixes #42838

Change-Id: I75ca0e98f3acfaa6366a26355dcd9dd82499a48b
Reviewed-on: https://go-review.googlesource.com/c/go/+/274442
Run-TryBot: Robert Griesemer 
TryBot-Result: Go Bot 
Reviewed-by: Robert Griesemer 
Reviewed-by: Matthew Dempsky 
Trust: Robert Griesemer

math/big: fix shift for recursive division

2020-11-12T20:42:40+00:00

The previous s value could cause a crash
for certain inputs.

Will check in tests and documentation improvements later.

Thanks to the Go Ethereum team and the OSS-Fuzz project for reporting this.
Thanks to Rémy Oudompheng and Robert Griesemer for their help
developing and validating the fix.

Fixes CVE-2020-28362

Change-Id: Ibbf455c4436bcdb07c84a34fa6551fb3422356d3
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/899974
Reviewed-by: Roland Shoemaker 
Reviewed-by: Filippo Valsorda 
Reviewed-on: https://go-review.googlesource.com/c/go/+/269657
Trust: Katie Hockman 
Trust: Roland Shoemaker 
Run-TryBot: Katie Hockman 
Reviewed-by: Roland Shoemaker 
TryBot-Result: Go Bot