cmd/internal/obj/arm64: optimize the instruction of moving long effective stack address

Currently, when the offset of "MOVD $offset(Rn), Rd" is a large positive
constant or a negative constant, the assembler will load this offset from
the constant pool.This patch gets rid of the constant pool by encoding the
offset into two ADD instructions if it's a large positive constant or one
SUB instruction if negative. For very large negative offset, it is rarely
used, here we don't optimize this case.

Optimized case 1: MOVD $-0x100000(R7), R0
Before: LDR 0x67670(constant pool), R27; ADD R27.UXTX, R0, R7
After: SUB $0x100000, R7, R0

Optimized case 2: MOVD $0x123468(R7), R0
Before: LDR 0x67670(constant pool), R27; ADD R27.UXTX, R0, R7
After: ADD $0x123000, R7, R27; ADD $0x000468, R27, R0

1. Binary size before/after.
binary                 size change
pkg/linux_arm64        +4KB
pkg/tool/linux_arm64   no change
go                     no change
gofmt                  no change

2. go1 benckmark.
name                      old time/op                new time/op                delta
pkg:test/bench/go1 goos:linux goarch:arm64
BinaryTree17-64           7335721401.800000ns +-40%  6264542009.800000ns +-14%    ~     (p=0.421 n=5+5)
Fannkuch11-64             3886551822.600000ns +- 0%  3875870590.200000ns +- 0%    ~     (p=0.151 n=5+5)
FmtFprintfEmpty-64                82.960000ns +- 1%          83.900000ns +- 2%  +1.13%  (p=0.048 n=5+5)
FmtFprintfString-64              149.200000ns +- 1%         148.000000ns +- 0%  -0.80%  (p=0.016 n=5+4)
FmtFprintfInt-64                 177.000000ns +- 0%         178.400000ns +- 2%    ~     (p=0.794 n=4+5)
FmtFprintfIntInt-64              240.200000ns +- 2%         239.400000ns +- 4%    ~     (p=0.302 n=5+5)
FmtFprintfPrefixedInt-64         300.400000ns +- 0%         299.200000ns +- 1%    ~     (p=0.119 n=5+5)
FmtFprintfFloat-64               360.000000ns +- 0%         361.600000ns +- 3%    ~     (p=0.349 n=4+5)
FmtManyArgs-64                  1064.400000ns +- 1%        1061.400000ns +- 0%    ~     (p=0.087 n=5+5)
GobDecode-64                12080404.400000ns +- 2%    11637601.000000ns +- 1%  -3.67%  (p=0.008 n=5+5)
GobEncode-64                 8474973.800000ns +- 2%     7977801.600000ns +- 2%  -5.87%  (p=0.008 n=5+5)
Gzip-64                    416501238.400000ns +- 0%   410463405.400000ns +- 0%  -1.45%  (p=0.008 n=5+5)
Gunzip-64                   58088415.200000ns +- 0%    58826209.600000ns +- 0%  +1.27%  (p=0.008 n=5+5)
HTTPClientServer-64           128660.200000ns +-23%      117840.800000ns +- 8%    ~     (p=0.222 n=5+5)
JSONEncode-64               17547746.800000ns +- 4%    17216180.000000ns +- 1%    ~     (p=0.222 n=5+5)
JSONDecode-64               80879896.000000ns +- 1%    80063737.200000ns +- 0%  -1.01%  (p=0.008 n=5+5)
Mandelbrot200-64             5484901.600000ns +- 0%     5483614.400000ns +- 0%    ~     (p=0.310 n=5+5)
GoParse-64                   6201166.800000ns +- 6%     6150920.600000ns +- 1%    ~     (p=0.548 n=5+5)
RegexpMatchEasy0_32-64           135.000000ns +- 0%         139.200000ns +- 7%    ~     (p=0.643 n=5+5)
RegexpMatchEasy0_1K-64           484.600000ns +- 2%         483.800000ns +- 2%    ~     (p=0.984 n=5+5)
RegexpMatchEasy1_32-64           128.000000ns +- 1%         124.600000ns +- 1%  -2.66%  (p=0.008 n=5+5)
RegexpMatchEasy1_1K-64           769.400000ns +- 2%         761.400000ns +- 1%    ~     (p=0.460 n=5+5)
RegexpMatchMedium_32-64           12.900000ns +- 0%          12.500000ns +- 0%  -3.10%  (p=0.008 n=5+5)
RegexpMatchMedium_1K-64        57879.200000ns +- 1%       56512.200000ns +- 0%  -2.36%  (p=0.008 n=5+5)
RegexpMatchHard_32-64           3091.600000ns +- 1%        3071.000000ns +- 0%  -0.67%  (p=0.048 n=5+5)
RegexpMatchHard_1K-64          92941.200000ns +- 1%       92794.000000ns +- 0%    ~     (p=1.000 n=5+5)
Revcomp-64                1695605187.000000ns +-54%  1821697637.400000ns +-47%    ~     (p=1.000 n=5+5)
Template-64                112839686.800000ns +- 1%   109964069.200000ns +- 3%    ~     (p=0.095 n=5+5)
TimeParse-64                     587.000000ns +- 0%         587.000000ns +- 0%    ~     (all equal)
TimeFormat-64                    586.000000ns +- 1%         584.200000ns +- 1%    ~     (p=0.659 n=5+5)
[Geo mean]                      81804.262218ns             80694.712973ns       -1.36%

name                      old speed                  new speed                  delta
pkg:test/bench/go1 goos:linux goarch:arm64
GobDecode-64                         63.6MB/s +- 2%             66.0MB/s +- 1%  +3.78%  (p=0.008 n=5+5)
GobEncode-64                         90.6MB/s +- 2%             96.2MB/s +- 2%  +6.23%  (p=0.008 n=5+5)
Gzip-64                              46.6MB/s +- 0%             47.3MB/s +- 0%  +1.47%  (p=0.008 n=5+5)
Gunzip-64                             334MB/s +- 0%              330MB/s +- 0%  -1.25%  (p=0.008 n=5+5)
JSONEncode-64                         111MB/s +- 4%              113MB/s +- 1%    ~     (p=0.222 n=5+5)
JSONDecode-64                        24.0MB/s +- 1%             24.2MB/s +- 0%  +1.02%  (p=0.008 n=5+5)
GoParse-64                           9.35MB/s +- 6%             9.42MB/s +- 1%    ~     (p=0.571 n=5+5)
RegexpMatchEasy0_32-64                237MB/s +- 0%              231MB/s +- 7%    ~     (p=0.690 n=5+5)
RegexpMatchEasy0_1K-64               2.11GB/s +- 2%             2.12GB/s +- 2%    ~     (p=1.000 n=5+5)
RegexpMatchEasy1_32-64                250MB/s +- 1%              257MB/s +- 1%  +2.63%  (p=0.008 n=5+5)
RegexpMatchEasy1_1K-64               1.33GB/s +- 2%             1.35GB/s +- 1%    ~     (p=0.548 n=5+5)
RegexpMatchMedium_32-64              77.6MB/s +- 0%             79.8MB/s +- 0%  +2.80%  (p=0.008 n=5+5)
RegexpMatchMedium_1K-64              17.7MB/s +- 1%             18.1MB/s +- 0%  +2.41%  (p=0.008 n=5+5)
RegexpMatchHard_32-64                10.4MB/s +- 1%             10.4MB/s +- 0%    ~     (p=0.056 n=5+5)
RegexpMatchHard_1K-64                11.0MB/s +- 1%             11.0MB/s +- 0%    ~     (p=0.984 n=5+5)
Revcomp-64                            188MB/s +-71%              155MB/s +-71%    ~     (p=1.000 n=5+5)
Template-64                          17.2MB/s +- 1%             17.7MB/s +- 3%    ~     (p=0.095 n=5+5)
[Geo mean]                            79.2MB/s                   79.3MB/s       +0.24%

Change-Id: I593ac3e7037afafc3605ad4b0cfb51d5dd88015d
Reviewed-on: https://go-review.googlesource.com/c/go/+/232438
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/cmd/internal/obj/arm64/a.out.go b/src/cmd/internal/obj/arm64/a.out.go
index 2839da1437..b3c9e9a18e 100644
--- a/src/cmd/internal/obj/arm64/a.out.go
+++ b/src/cmd/internal/obj/arm64/a.out.go
@@ -410,9 +410,10 @@ const (
 	C_FCON     // floating-point constant
 	C_VCONADDR // 64-bit memory address
 
-	C_AACON // ADDCON offset in auto constant $a(FP)
-	C_LACON // 32-bit offset in auto constant $a(FP)
-	C_AECON // ADDCON offset in extern constant $e(SB)
+	C_AACON  // ADDCON offset in auto constant $a(FP)
+	C_AACON2 // 24-bit offset in auto constant $a(FP)
+	C_LACON  // 32-bit offset in auto constant $a(FP)
+	C_AECON  // ADDCON offset in extern constant $e(SB)
 
 	// TODO(aram): only one branch class should be enough
 	C_SBRA // for TYPE_BRANCH