[release-branch.go1.10] bytes, strings: fix comparison of long byte slices on s390x

The existing implementation of bytes.Compare on s390x doesn't work properly for slices longer
than 256 elements. This change fixes that. Added tests for long strings and slices of bytes.

Fixes #26117

Change-Id: If6d8b68ee6dbcf99a24f867a1d3438b1f208954f
Reviewed-on: https://go-review.googlesource.com/121495
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/124016
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/bytes/compare_test.go b/src/bytes/compare_test.go
index 35088a1b2e9b26691a6f0a0bed6611e0bb6b563e..3e33c27c9c961164419f1c2b68f80c96e5a8aa1f 100644 (file)
--- a/src/bytes/compare_test.go
+++ b/src/bytes/compare_test.go
@@ -6,6 +6,7 @@ package bytes_test
 
 import (
        . "bytes"
+       "internal/testenv"
        "testing"
 )
 
@@ -58,10 +59,20 @@ func TestCompareIdenticalSlice(t *testing.T) {
 }
 
 func TestCompareBytes(t *testing.T) {
-       n := 128
+       lengths := make([]int, 0) // lengths to test in ascending order
+       for i := 0; i <= 128; i++ {
+               lengths = append(lengths, i)
+       }
+       lengths = append(lengths, 256, 512, 1024, 1333, 4095, 4096, 4097)
+
+       if !testing.Short() || testenv.Builder() != "" {
+               lengths = append(lengths, 65535, 65536, 65537, 99999)
+       }
+
+       n := lengths[len(lengths)-1]
        a := make([]byte, n+1)
        b := make([]byte, n+1)
-       for len := 0; len < 128; len++ {
+       for _, len := range lengths {
                // randomish but deterministic data. No 0 or 255.
                for i := 0; i < len; i++ {
                        a[i] = byte(1 + 31*i%254)

diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 6b71830557707b64ae950f71d8b925e2d614710b..8b7a98d0c8c67a9234b43f4c58968690f481de63 100644 (file)
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -1032,6 +1032,8 @@ loop:
        BGT     gt
        BLT     lt
        SUB     $256, R8
+       MOVD    $256(R3), R3
+       MOVD    $256(R5), R5
        CMP     R8, $256
        BGT     loop
 tail:

diff --git a/src/strings/compare_test.go b/src/strings/compare_test.go
index bc12e421b0dd7919b680a641da1b96c5bb951631..712e5a741eae2878e33de6d488a9bf25f5efb0fe 100644 (file)
--- a/src/strings/compare_test.go
+++ b/src/strings/compare_test.go
@@ -8,6 +8,7 @@ package strings_test
 // Benchmarks omitted since the underlying implementation is identical.
 
 import (
+       "internal/testenv"
        . "strings"
        "testing"
 )
@@ -52,10 +53,20 @@ func TestCompareIdenticalString(t *testing.T) {
 }
 
 func TestCompareStrings(t *testing.T) {
-       n := 128
+       lengths := make([]int, 0) // lengths to test in ascending order
+       for i := 0; i <= 128; i++ {
+               lengths = append(lengths, i)
+       }
+       lengths = append(lengths, 256, 512, 1024, 1333, 4095, 4096, 4097)
+
+       if !testing.Short() || testenv.Builder() != "" {
+               lengths = append(lengths, 65535, 65536, 65537, 99999)
+       }
+
+       n := lengths[len(lengths)-1]
        a := make([]byte, n+1)
        b := make([]byte, n+1)
-       for len := 0; len < 128; len++ {
+       for _, len := range lengths {
                // randomish but deterministic data. No 0 or 255.
                for i := 0; i < len; i++ {
                        a[i] = byte(1 + 31*i%254)