From: Guoqi Chen <chenguoqi@loongson.cn>
Date: Wed, 4 Feb 2026 07:25:07 +0000 (+0800)
Subject: cmd/compile: allow equal functions to perform unaligned load on loong64
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=045ceb72406ee725fd0ea9b8267e8bcd4d2afd5b;p=gostls13.git

cmd/compile: allow equal functions to perform unaligned load on loong64

The Go compiler always generates Loong64 binaries, which can execute any
processor of LA364, LA464, LA664 or higher core. And these processors
support unaligned memory access [1].

goos: linux
goarch: loong64
pkg: strings
cpu: Loongson-3A6000 @ 2500.00MHz
              |   old.txt    |               new.txt                |
              |    sec/op    |    sec/op     vs base                |
StringPrefix3   4.0040n ± 0%   0.4003n ± 0%  -90.00% (p=0.000 n=10)
StringPrefix5   4.0040n ± 0%   0.4003n ± 0%  -90.00% (p=0.000 n=10)
StringPrefix6   3.6030n ± 0%   0.4002n ± 0%  -88.89% (p=0.000 n=10)
StringPrefix7   4.0040n ± 0%   0.4002n ± 0%  -90.00% (p=0.000 n=10)
geomean          3.900n        0.4003n       -89.74%

goos: linux
goarch: loong64
pkg: strings
cpu: Loongson-3A5000-HV @ 2500.00MHz
              |   old.txt    │               new.txt                |
              |    sec/op    │    sec/op     vs base                |
StringPrefix3   5.6160n ± 0%   0.4011n ± 0%  -92.86% (p=0.000 n=10)
StringPrefix5   5.6180n ± 0%   0.4011n ± 0%  -92.86% (p=0.000 n=10)
StringPrefix6   5.2170n ± 0%   0.4011n ± 0%  -92.31% (p=0.000 n=10)
StringPrefix7   5.6170n ± 0%   0.4009n ± 0%  -92.86% (p=0.000 n=10)
geomean          5.514n        0.4010n       -92.73%

goos: linux
goarch: loong64
pkg: strings
cpu: Loongson-3B6000M @ 2400.00MHz
              |   old.txt    │               new.txt                |
              |    sec/op    │    sec/op     vs base                |
StringPrefix3   5.0060n ± 0%   0.4223n ± 1%  -91.56% (p=0.000 n=10)
StringPrefix5   4.5890n ± 0%   0.4214n ± 0%  -90.82% (p=0.000 n=10)
StringPrefix6   4.5890n ± 0%   0.4190n ± 1%  -90.87% (p=0.000 n=10)
StringPrefix7   4.5890n ± 0%   0.4226n ± 1%  -90.79% (p=0.000 n=10)
geomean          4.690n        0.4213n       -91.02%

[1]: https://go.dev/wiki/MinimumRequirements#loong64

Change-Id: I1870080e0122a7d136685e3045699d0cf1e4194d
Reviewed-on: https://go-review.googlesource.com/c/go/+/742260
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
---

diff --git a/src/cmd/internal/sys/arch.go b/src/cmd/internal/sys/arch.go
index 14b1cde22b..2738fe3b54 100644
--- a/src/cmd/internal/sys/arch.go
+++ b/src/cmd/internal/sys/arch.go
@@ -143,7 +143,7 @@ var ArchLoong64 = &Arch{
 	PtrSize:        8,
 	RegSize:        8,
 	MinLC:          4,
-	Alignment:      8, // Unaligned accesses are not guaranteed to be fast
+	Alignment:      1,
 	CanMergeLoads:  true,
 	CanJumpTable:   true,
 	HasLR:          true,
diff --git a/test/codegen/comparisons.go b/test/codegen/comparisons.go
index 70852377f7..330497c656 100644
--- a/test/codegen/comparisons.go
+++ b/test/codegen/comparisons.go
@@ -597,6 +597,7 @@ func equalConstString1() bool {
 	b := string("Z")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a == b
 }
@@ -605,6 +606,7 @@ func equalVarString1(a string) bool {
 	b := string("Z")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a[:1] == b
 }
@@ -614,6 +616,7 @@ func equalConstString2() bool {
 	b := string("ZZ")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a == b
 }
@@ -622,6 +625,7 @@ func equalVarString2(a string) bool {
 	b := string("ZZ")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a[:2] == b
 }
@@ -631,6 +635,7 @@ func equalConstString4() bool {
 	b := string("ZZZZ")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a == b
 }
@@ -639,6 +644,7 @@ func equalVarString4(a string) bool {
 	b := string("ZZZZ")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a[:4] == b
 }
@@ -648,6 +654,7 @@ func equalConstString8() bool {
 	b := string("ZZZZZZZZ")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a == b
 }
@@ -656,6 +663,7 @@ func equalVarString8(a string) bool {
 	b := string("ZZZZZZZZ")
 	// amd64:-".*memequal"
 	// arm64:-".*memequal"
+	// loong64:-".*memequal"
 	// ppc64x:-".*memequal"
 	return a[:8] == b
 }