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e031318ca6
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Xiangdong Ji e031318ca6 cmd/compile: ARM comparisons with 0 incorrect on overflow 
Some ARM rewriting rules convert 'comparing to zero' conditions of if
statements to a simplified version utilizing CMN and CMP instructions to
branch over condition flags, in order to save one Add or Sub caculation.

Such optimizations lead to wrong branching in case an overflow/underflow
occurs when executing CMN or CMP.

Fix the issue by introducing new block opcodes that don't honor the
overflow/underflow flag:

  Block-Op         Meaning                   ARM condition codes
  1. LTnoov        less than                 MI
  2. GEnoov        greater than or equal     PL
  3. LEnoov        less than or equal        MI || EQ
  4. GTnoov        greater than              NEQ & PL

The patch also adds a few test cases to cover scenarios that are specific
to ARM and fine-tunes the code generation tests for 'x-const'.

For more details please refer to the previous fix on 64-bit ARM:
  https://go-review.googlesource.com/c/go/+/233097

Go1 perf, 'old' is the non-optimized version, that is removing all concerned
rewriting rules.

name                     old time/op    new time/op     delta
BinaryTree17-8              7.73s ± 0%      7.81s ± 0%  +0.97%  (p=0.000 n=7+8)
Fannkuch11-8                7.06s ± 0%      7.00s ± 0%  -0.83%  (p=0.000 n=8+8)
FmtFprintfEmpty-8           181ns ± 1%      183ns ± 1%  +1.31%  (p=0.001 n=8+8)
FmtFprintfString-8          319ns ± 1%      325ns ± 2%  +1.71%  (p=0.009 n=7+8)
FmtFprintfInt-8             358ns ± 1%      359ns ± 1%    ~     (p=0.293 n=7+7)
FmtFprintfIntInt-8          459ns ± 3%      456ns ± 1%    ~     (p=0.869 n=8+8)
FmtFprintfPrefixedInt-8     535ns ± 4%      538ns ± 4%    ~     (p=0.572 n=8+8)
FmtFprintfFloat-8          1.01µs ± 2%     1.01µs ± 2%    ~     (p=0.625 n=8+8)
FmtManyArgs-8              1.93µs ± 2%     1.93µs ± 1%    ~     (p=0.979 n=8+7)
GobDecode-8                16.1ms ± 1%     16.5ms ± 1%  +2.32%  (p=0.000 n=8+8)
GobEncode-8                15.9ms ± 0%     15.8ms ± 1%  -1.00%  (p=0.000 n=8+7)
Gzip-8                      690ms ± 1%      670ms ± 0%  -2.90%  (p=0.000 n=8+8)
Gunzip-8                    109ms ± 1%      109ms ± 1%    ~     (p=0.694 n=7+8)
HTTPClientServer-8          149µs ± 3%      146µs ± 2%  -1.70%  (p=0.028 n=8+8)
JSONEncode-8               50.5ms ± 1%     49.2ms ± 0%  -2.60%  (p=0.001 n=7+7)
JSONDecode-8                135ms ± 2%      137ms ± 1%    ~     (p=0.054 n=8+7)
Mandelbrot200-8             951ms ± 0%      952ms ± 0%    ~     (p=0.852 n=6+8)
GoParse-8                  9.47ms ± 1%     9.66ms ± 1%  +2.01%  (p=0.000 n=8+8)
RegexpMatchEasy0_32-8       288ns ± 2%      277ns ± 2%  -3.61%  (p=0.000 n=8+8)
RegexpMatchEasy0_1K-8      1.66µs ± 1%     1.69µs ± 2%  +2.21%  (p=0.001 n=7+7)
RegexpMatchEasy1_32-8       334ns ± 1%      305ns ± 2%  -8.86%  (p=0.000 n=8+8)
RegexpMatchEasy1_1K-8      2.14µs ± 2%     2.15µs ± 0%    ~     (p=0.099 n=8+8)
RegexpMatchMedium_32-8     13.3ns ± 1%     13.3ns ± 0%    ~     (p=1.000 n=7+7)
RegexpMatchMedium_1K-8     81.1µs ± 3%     80.7µs ± 1%    ~     (p=0.955 n=7+8)
RegexpMatchHard_32-8       4.26µs ± 0%     4.26µs ± 0%    ~     (p=0.933 n=7+8)
RegexpMatchHard_1K-8        124µs ± 0%      124µs ± 0%  +0.31%  (p=0.000 n=8+8)
Revcomp-8                  14.7ms ± 2%     14.5ms ± 1%  -1.66%  (p=0.003 n=8+8)
Template-8                  197ms ± 2%      200ms ± 3%  +1.62%  (p=0.021 n=8+8)
TimeParse-8                1.33µs ± 1%     1.30µs ± 1%  -1.86%  (p=0.002 n=8+8)
TimeFormat-8               3.04µs ± 1%     3.02µs ± 0%  -0.60%  (p=0.000 n=8+8)

name                     old speed      new speed       delta
GobDecode-8              47.6MB/s ± 1%   46.5MB/s ± 1%  -2.28%  (p=0.000 n=8+8)
GobEncode-8              48.1MB/s ± 0%   48.6MB/s ± 1%  +1.02%  (p=0.000 n=8+7)
Gzip-8                   28.1MB/s ± 1%   29.0MB/s ± 0%  +2.97%  (p=0.000 n=8+8)
Gunzip-8                  178MB/s ± 1%    179MB/s ± 2%    ~     (p=0.694 n=7+8)
JSONEncode-8             38.4MB/s ± 1%   39.4MB/s ± 0%  +2.67%  (p=0.001 n=7+7)
JSONDecode-8             14.3MB/s ± 2%   14.2MB/s ± 1%  -0.81%  (p=0.043 n=8+7)
GoParse-8                6.12MB/s ± 1%   5.99MB/s ± 1%  -2.00%  (p=0.000 n=8+8)
RegexpMatchEasy0_32-8     111MB/s ± 2%    115MB/s ± 2%  +3.77%  (p=0.000 n=8+8)
RegexpMatchEasy0_1K-8     618MB/s ± 1%    604MB/s ± 2%  -2.16%  (p=0.001 n=7+7)
RegexpMatchEasy1_32-8    95.7MB/s ± 1%  105.1MB/s ± 2%  +9.76%  (p=0.000 n=8+8)
RegexpMatchEasy1_1K-8     479MB/s ± 2%    477MB/s ± 0%    ~     (p=0.105 n=8+8)
RegexpMatchMedium_32-8   75.2MB/s ± 1%   75.2MB/s ± 0%    ~     (p=0.247 n=7+7)
RegexpMatchMedium_1K-8   12.6MB/s ± 3%   12.7MB/s ± 1%    ~     (p=0.538 n=7+8)
RegexpMatchHard_32-8     7.52MB/s ± 0%   7.52MB/s ± 0%    ~     (p=0.968 n=7+8)
RegexpMatchHard_1K-8     8.26MB/s ± 0%   8.24MB/s ± 0%  -0.30%  (p=0.001 n=8+8)
Revcomp-8                 173MB/s ± 2%    176MB/s ± 1%  +1.68%  (p=0.003 n=8+8)
Template-8               9.85MB/s ± 2%   9.69MB/s ± 3%  -1.59%  (p=0.021 n=8+8)

Fixes   #39303
Updates #38740

Change-Id: I0a5f87bfda679f66414c0041ace2ca2e28363f36
Reviewed-on: https://go-review.googlesource.com/c/go/+/236637
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2020-06-09 15:50:33 +00:00
.github .github: add link to questions in ISSUE_TEMPLATE 2020-01-06 17:05:31 +00:00
api all: remove scattered remnants of darwin/386 2020-04-08 18:37:38 +00:00
doc doc/go1.15: remove TODO in minor library changes section 2020-06-09 15:44:15 +00:00
lib/time lib/time, time/tzdata: update tz data to 2020a 2020-04-30 08:07:39 +00:00
misc misc/cgo/testplugin: fix typo in comment 2020-06-01 23:25:14 +00:00
src cmd/compile: ARM comparisons with 0 incorrect on overflow 2020-06-09 15:50:33 +00:00
test cmd/compile: ARM comparisons with 0 incorrect on overflow 2020-06-09 15:50:33 +00:00
.gitattributes all: treat all files as binary, but check in .bat with CRLF 2020-06-08 15:31:43 +00:00
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A+C: add Prasanga Siripala (individual CLA) 2020-05-12 19:15:34 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
CONTRIBUTORS A+C: add Prasanga Siripala (individual CLA) 2020-05-12 19:15:34 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
robots.txt
SECURITY.md SECURITY.md: update go versions 2019-09-26 15:34:57 +00:00

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