sha3: reenable s390x assembly

Fixes golang/go#64897

Change-Id: I0c8c52d73a7d2df0f44fee36d407a87213f59bff
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/554435
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

sha3/allocations_test.go

@@ -7,6 +7,7 @@
 package sha3_test
 
 import (
+	"runtime"
 	"testing"
 
 	"golang.org/x/crypto/sha3"
@@ -15,6 +16,13 @@ import (
 var sink byte
 
 func TestAllocations(t *testing.T) {
+	want := 0.0
+
+	if runtime.GOARCH == "s390x" {
+		// On s390x the returned hash.Hash is conditional so it escapes.
+		want = 3.0
+	}
+
 	t.Run("New", func(t *testing.T) {
 		if allocs := testing.AllocsPerRun(10, func() {
 			h := sha3.New256()
@@ -23,7 +31,7 @@ func TestAllocations(t *testing.T) {
 			out := make([]byte, 0, 32)
 			out = h.Sum(out)
 			sink ^= out[0]
-		}); allocs > 0 {
+		}); allocs > want {
 			t.Errorf("expected zero allocations, got %0.1f", allocs)
 		}
 	})
@@ -37,7 +45,7 @@ func TestAllocations(t *testing.T) {
 			sink ^= out[0]
 			h.Read(out)
 			sink ^= out[0]
-		}); allocs > 0 {
+		}); allocs > want {
 			t.Errorf("expected zero allocations, got %0.1f", allocs)
 		}
 	})
@@ -46,7 +54,7 @@ func TestAllocations(t *testing.T) {
 			b := []byte("ABC")
 			out := sha3.Sum256(b)
 			sink ^= out[0]
-		}); allocs > 0 {
+		}); allocs > want {
 			t.Errorf("expected zero allocations, got %0.1f", allocs)
 		}
 	})