diff --git a/README.md b/README.md
index 1a100b36..b4800b33 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,7 @@ Building gonum applications will work without knowing how to use these tags, but
 The current list of non-internal tags is as follows:
 
 - appengine — do not use assembly or unsafe
+- safe — synonym for appengine
 - bounds — use bounds checks even in internal calls
 - cblas — use CGO gonum.org/v1/netlib/blas/netlib BLAS implementation in tests (only in [mat package](https://godoc.org/gonum.org/v1/gonum/mat))
 - noasm — do not use assembly implementations
diff --git a/graph/internal/set/same.go b/graph/internal/set/same.go
index 75718e0b..f95a4e12 100644
--- a/graph/internal/set/same.go
+++ b/graph/internal/set/same.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !appengine
+// +build !appengine,!safe
 
 package set
 
diff --git a/graph/internal/set/same_appengine.go b/graph/internal/set/same_appengine.go
index cd52a8f6..4ff4f4ed 100644
--- a/graph/internal/set/same_appengine.go
+++ b/graph/internal/set/same_appengine.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build appengine
+// +build appengine safe
 
 package set
 
diff --git a/internal/asm/c128/axpyinc_amd64.s b/internal/asm/c128/axpyinc_amd64.s
index 2ae34daa..0a4c14c2 100644
--- a/internal/asm/c128/axpyinc_amd64.s
+++ b/internal/asm/c128/axpyinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/axpyincto_amd64.s b/internal/asm/c128/axpyincto_amd64.s
index 127e4891..cb57f4be 100644
--- a/internal/asm/c128/axpyincto_amd64.s
+++ b/internal/asm/c128/axpyincto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/axpyunitary_amd64.s b/internal/asm/c128/axpyunitary_amd64.s
index 2a6c80e0..f1fddce7 100644
--- a/internal/asm/c128/axpyunitary_amd64.s
+++ b/internal/asm/c128/axpyunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/axpyunitaryto_amd64.s b/internal/asm/c128/axpyunitaryto_amd64.s
index db5b3355..b80015fd 100644
--- a/internal/asm/c128/axpyunitaryto_amd64.s
+++ b/internal/asm/c128/axpyunitaryto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/dotcinc_amd64.s b/internal/asm/c128/dotcinc_amd64.s
index ce664235..301d294f 100644
--- a/internal/asm/c128/dotcinc_amd64.s
+++ b/internal/asm/c128/dotcinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/dotcunitary_amd64.s b/internal/asm/c128/dotcunitary_amd64.s
index 34e78b85..1db7e156 100644
--- a/internal/asm/c128/dotcunitary_amd64.s
+++ b/internal/asm/c128/dotcunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/dotuinc_amd64.s b/internal/asm/c128/dotuinc_amd64.s
index 59eccf2b..386467fc 100644
--- a/internal/asm/c128/dotuinc_amd64.s
+++ b/internal/asm/c128/dotuinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/dotuunitary_amd64.s b/internal/asm/c128/dotuunitary_amd64.s
index 7f1de266..d0d507cd 100644
--- a/internal/asm/c128/dotuunitary_amd64.s
+++ b/internal/asm/c128/dotuunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/dscalinc_amd64.s b/internal/asm/c128/dscalinc_amd64.s
index 78ee18a8..40d5851a 100644
--- a/internal/asm/c128/dscalinc_amd64.s
+++ b/internal/asm/c128/dscalinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/dscalunitary_amd64.s b/internal/asm/c128/dscalunitary_amd64.s
index c68b5a6b..cbc0768a 100644
--- a/internal/asm/c128/dscalunitary_amd64.s
+++ b/internal/asm/c128/dscalunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/scalUnitary_amd64.s b/internal/asm/c128/scalUnitary_amd64.s
index 17c3ef46..7b807b3a 100644
--- a/internal/asm/c128/scalUnitary_amd64.s
+++ b/internal/asm/c128/scalUnitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/scalinc_amd64.s b/internal/asm/c128/scalinc_amd64.s
index 17884cb6..7857c155 100644
--- a/internal/asm/c128/scalinc_amd64.s
+++ b/internal/asm/c128/scalinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c128/stubs_amd64.go b/internal/asm/c128/stubs_amd64.go
index 68c92d20..ad6b23ca 100644
--- a/internal/asm/c128/stubs_amd64.go
+++ b/internal/asm/c128/stubs_amd64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package c128
 
diff --git a/internal/asm/c128/stubs_noasm.go b/internal/asm/c128/stubs_noasm.go
index 47930bb4..6313e571 100644
--- a/internal/asm/c128/stubs_noasm.go
+++ b/internal/asm/c128/stubs_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package c128
 
diff --git a/internal/asm/c64/axpyinc_amd64.s b/internal/asm/c64/axpyinc_amd64.s
index 2f1b2659..841415db 100644
--- a/internal/asm/c64/axpyinc_amd64.s
+++ b/internal/asm/c64/axpyinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/axpyincto_amd64.s b/internal/asm/c64/axpyincto_amd64.s
index 8d521404..5c5228dc 100644
--- a/internal/asm/c64/axpyincto_amd64.s
+++ b/internal/asm/c64/axpyincto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/axpyunitary_amd64.s b/internal/asm/c64/axpyunitary_amd64.s
index 64e4fdcb..ae744a49 100644
--- a/internal/asm/c64/axpyunitary_amd64.s
+++ b/internal/asm/c64/axpyunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/axpyunitaryto_amd64.s b/internal/asm/c64/axpyunitaryto_amd64.s
index 9549b13b..a5d70209 100644
--- a/internal/asm/c64/axpyunitaryto_amd64.s
+++ b/internal/asm/c64/axpyunitaryto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/dotcinc_amd64.s b/internal/asm/c64/dotcinc_amd64.s
index 11c5b286..87de31d3 100644
--- a/internal/asm/c64/dotcinc_amd64.s
+++ b/internal/asm/c64/dotcinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/dotcunitary_amd64.s b/internal/asm/c64/dotcunitary_amd64.s
index 476df575..d53479ca 100644
--- a/internal/asm/c64/dotcunitary_amd64.s
+++ b/internal/asm/c64/dotcunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/dotuinc_amd64.s b/internal/asm/c64/dotuinc_amd64.s
index 1c2a069a..bdee59be 100644
--- a/internal/asm/c64/dotuinc_amd64.s
+++ b/internal/asm/c64/dotuinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/dotuunitary_amd64.s b/internal/asm/c64/dotuunitary_amd64.s
index 6b35002f..dce83a46 100644
--- a/internal/asm/c64/dotuunitary_amd64.s
+++ b/internal/asm/c64/dotuunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/c64/stubs_amd64.go b/internal/asm/c64/stubs_amd64.go
index 636c64af..3e12d6bc 100644
--- a/internal/asm/c64/stubs_amd64.go
+++ b/internal/asm/c64/stubs_amd64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package c64
 
diff --git a/internal/asm/c64/stubs_noasm.go b/internal/asm/c64/stubs_noasm.go
index 5ef7a2eb..411afcb2 100644
--- a/internal/asm/c64/stubs_noasm.go
+++ b/internal/asm/c64/stubs_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package c64
 
diff --git a/internal/asm/f32/axpyinc_amd64.s b/internal/asm/f32/axpyinc_amd64.s
index 2b3126f4..2d167c08 100644
--- a/internal/asm/f32/axpyinc_amd64.s
+++ b/internal/asm/f32/axpyinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/axpyincto_amd64.s b/internal/asm/f32/axpyincto_amd64.s
index 8100a750..b79f9926 100644
--- a/internal/asm/f32/axpyincto_amd64.s
+++ b/internal/asm/f32/axpyincto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/axpyunitary_amd64.s b/internal/asm/f32/axpyunitary_amd64.s
index d14230b9..97df90a0 100644
--- a/internal/asm/f32/axpyunitary_amd64.s
+++ b/internal/asm/f32/axpyunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/axpyunitaryto_amd64.s b/internal/asm/f32/axpyunitaryto_amd64.s
index 0ed8a449..a826ca31 100644
--- a/internal/asm/f32/axpyunitaryto_amd64.s
+++ b/internal/asm/f32/axpyunitaryto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/ddotinc_amd64.s b/internal/asm/f32/ddotinc_amd64.s
index 68c7fa9d..4518e049 100644
--- a/internal/asm/f32/ddotinc_amd64.s
+++ b/internal/asm/f32/ddotinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/ddotunitary_amd64.s b/internal/asm/f32/ddotunitary_amd64.s
index 47d24ab5..231cbd3b 100644
--- a/internal/asm/f32/ddotunitary_amd64.s
+++ b/internal/asm/f32/ddotunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/dotinc_amd64.s b/internal/asm/f32/dotinc_amd64.s
index 00a382b5..4d36b289 100644
--- a/internal/asm/f32/dotinc_amd64.s
+++ b/internal/asm/f32/dotinc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/dotunitary_amd64.s b/internal/asm/f32/dotunitary_amd64.s
index 581a8f4c..c32ede5a 100644
--- a/internal/asm/f32/dotunitary_amd64.s
+++ b/internal/asm/f32/dotunitary_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/ge_amd64.go b/internal/asm/f32/ge_amd64.go
index f466d8e0..2b336a2a 100644
--- a/internal/asm/f32/ge_amd64.go
+++ b/internal/asm/f32/ge_amd64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package f32
 
diff --git a/internal/asm/f32/ge_amd64.s b/internal/asm/f32/ge_amd64.s
index b7836559..e5e80c52 100644
--- a/internal/asm/f32/ge_amd64.s
+++ b/internal/asm/f32/ge_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f32/ge_noasm.go b/internal/asm/f32/ge_noasm.go
index cd701a39..d92f9968 100644
--- a/internal/asm/f32/ge_noasm.go
+++ b/internal/asm/f32/ge_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f32
 
diff --git a/internal/asm/f32/stubs_amd64.go b/internal/asm/f32/stubs_amd64.go
index 794d00f7..fcbce09e 100644
--- a/internal/asm/f32/stubs_amd64.go
+++ b/internal/asm/f32/stubs_amd64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package f32
 
diff --git a/internal/asm/f32/stubs_noasm.go b/internal/asm/f32/stubs_noasm.go
index 6f0aeccd..3b5b0970 100644
--- a/internal/asm/f32/stubs_noasm.go
+++ b/internal/asm/f32/stubs_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f32
 
diff --git a/internal/asm/f64/abssum_amd64.s b/internal/asm/f64/abssum_amd64.s
index 1677401a..d9d61bb7 100644
--- a/internal/asm/f64/abssum_amd64.s
+++ b/internal/asm/f64/abssum_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/abssuminc_amd64.s b/internal/asm/f64/abssuminc_amd64.s
index b44ea121..cac19aa6 100644
--- a/internal/asm/f64/abssuminc_amd64.s
+++ b/internal/asm/f64/abssuminc_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/add_amd64.s b/internal/asm/f64/add_amd64.s
index a8e6818c..bc0ea6a4 100644
--- a/internal/asm/f64/add_amd64.s
+++ b/internal/asm/f64/add_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/addconst_amd64.s b/internal/asm/f64/addconst_amd64.s
index 44b97231..7cc68c78 100644
--- a/internal/asm/f64/addconst_amd64.s
+++ b/internal/asm/f64/addconst_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/axpy.go b/internal/asm/f64/axpy.go
index b1668e75..b8322139 100644
--- a/internal/asm/f64/axpy.go
+++ b/internal/asm/f64/axpy.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f64
 
diff --git a/internal/asm/f64/axpyinc_amd64.s b/internal/asm/f64/axpyinc_amd64.s
index a8607fe4..95fe9f90 100644
--- a/internal/asm/f64/axpyinc_amd64.s
+++ b/internal/asm/f64/axpyinc_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/axpyincto_amd64.s b/internal/asm/f64/axpyincto_amd64.s
index 0fceca6b..dcb79d87 100644
--- a/internal/asm/f64/axpyincto_amd64.s
+++ b/internal/asm/f64/axpyincto_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/axpyunitary_amd64.s b/internal/asm/f64/axpyunitary_amd64.s
index e37011df..bc290a15 100644
--- a/internal/asm/f64/axpyunitary_amd64.s
+++ b/internal/asm/f64/axpyunitary_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/axpyunitaryto_amd64.s b/internal/asm/f64/axpyunitaryto_amd64.s
index c9cda0b0..16798eba 100644
--- a/internal/asm/f64/axpyunitaryto_amd64.s
+++ b/internal/asm/f64/axpyunitaryto_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/cumprod_amd64.s b/internal/asm/f64/cumprod_amd64.s
index a4d34d8b..32bd1572 100644
--- a/internal/asm/f64/cumprod_amd64.s
+++ b/internal/asm/f64/cumprod_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/cumsum_amd64.s b/internal/asm/f64/cumsum_amd64.s
index 757eccdc..10d7fdab 100644
--- a/internal/asm/f64/cumsum_amd64.s
+++ b/internal/asm/f64/cumsum_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/div_amd64.s b/internal/asm/f64/div_amd64.s
index f3fc1e17..1a4e9eec 100644
--- a/internal/asm/f64/div_amd64.s
+++ b/internal/asm/f64/div_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/divto_amd64.s b/internal/asm/f64/divto_amd64.s
index e30e8078..16ab9b7e 100644
--- a/internal/asm/f64/divto_amd64.s
+++ b/internal/asm/f64/divto_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/dot.go b/internal/asm/f64/dot.go
index 909509a2..b77138d1 100644
--- a/internal/asm/f64/dot.go
+++ b/internal/asm/f64/dot.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f64
 
diff --git a/internal/asm/f64/dot_amd64.s b/internal/asm/f64/dot_amd64.s
index 79852d1e..eff25059 100644
--- a/internal/asm/f64/dot_amd64.s
+++ b/internal/asm/f64/dot_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/ge_amd64.go b/internal/asm/f64/ge_amd64.go
index dd27779a..00c99e93 100644
--- a/internal/asm/f64/ge_amd64.go
+++ b/internal/asm/f64/ge_amd64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package f64
 
diff --git a/internal/asm/f64/ge_noasm.go b/internal/asm/f64/ge_noasm.go
index 2150b87f..5a2c1d35 100644
--- a/internal/asm/f64/ge_noasm.go
+++ b/internal/asm/f64/ge_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f64
 
diff --git a/internal/asm/f64/gemvN_amd64.s b/internal/asm/f64/gemvN_amd64.s
index aab7dd51..2abdddd8 100644
--- a/internal/asm/f64/gemvN_amd64.s
+++ b/internal/asm/f64/gemvN_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/gemvT_amd64.s b/internal/asm/f64/gemvT_amd64.s
index 8c0a6b0b..87ba5cbf 100644
--- a/internal/asm/f64/gemvT_amd64.s
+++ b/internal/asm/f64/gemvT_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/ger_amd64.s b/internal/asm/f64/ger_amd64.s
index 584bc3a2..8c1b36a6 100644
--- a/internal/asm/f64/ger_amd64.s
+++ b/internal/asm/f64/ger_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/l1norm_amd64.s b/internal/asm/f64/l1norm_amd64.s
index ae140701..f87f856c 100644
--- a/internal/asm/f64/l1norm_amd64.s
+++ b/internal/asm/f64/l1norm_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/linfnorm_amd64.s b/internal/asm/f64/linfnorm_amd64.s
index a6d37461..b0625928 100644
--- a/internal/asm/f64/linfnorm_amd64.s
+++ b/internal/asm/f64/linfnorm_amd64.s
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/scal.go b/internal/asm/f64/scal.go
index 745dd5eb..3cc7aca6 100644
--- a/internal/asm/f64/scal.go
+++ b/internal/asm/f64/scal.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f64
 
diff --git a/internal/asm/f64/scalinc_amd64.s b/internal/asm/f64/scalinc_amd64.s
index 044d4e93..fb8b545e 100644
--- a/internal/asm/f64/scalinc_amd64.s
+++ b/internal/asm/f64/scalinc_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/scalincto_amd64.s b/internal/asm/f64/scalincto_amd64.s
index 47e43b1c..186fd1c0 100644
--- a/internal/asm/f64/scalincto_amd64.s
+++ b/internal/asm/f64/scalincto_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/scalunitary_amd64.s b/internal/asm/f64/scalunitary_amd64.s
index 43102f84..f852c7f7 100644
--- a/internal/asm/f64/scalunitary_amd64.s
+++ b/internal/asm/f64/scalunitary_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/scalunitaryto_amd64.s b/internal/asm/f64/scalunitaryto_amd64.s
index 71b5313b..d2b607f5 100644
--- a/internal/asm/f64/scalunitaryto_amd64.s
+++ b/internal/asm/f64/scalunitaryto_amd64.s
@@ -34,7 +34,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 #include "textflag.h"
 
diff --git a/internal/asm/f64/stubs_amd64.go b/internal/asm/f64/stubs_amd64.go
index 6116d58b..f6cf96ca 100644
--- a/internal/asm/f64/stubs_amd64.go
+++ b/internal/asm/f64/stubs_amd64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package f64
 
diff --git a/internal/asm/f64/stubs_noasm.go b/internal/asm/f64/stubs_noasm.go
index b0be9406..eae620b1 100644
--- a/internal/asm/f64/stubs_noasm.go
+++ b/internal/asm/f64/stubs_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package f64
 
diff --git a/internal/math32/sqrt.go b/internal/math32/sqrt.go
index 36074122..bf630de9 100644
--- a/internal/math32/sqrt.go
+++ b/internal/math32/sqrt.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64 noasm appengine
+// +build !amd64 noasm appengine safe
 
 package math32
 
diff --git a/internal/math32/sqrt_amd64.go b/internal/math32/sqrt_amd64.go
index 633f933a..905ae5c6 100644
--- a/internal/math32/sqrt_amd64.go
+++ b/internal/math32/sqrt_amd64.go
@@ -6,7 +6,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !noasm,!appengine
+// +build !noasm,!appengine,!safe
 
 package math32
 
diff --git a/internal/math32/sqrt_amd64.s b/internal/math32/sqrt_amd64.s
index 6df2ce7d..fa2b8696 100644
--- a/internal/math32/sqrt_amd64.s
+++ b/internal/math32/sqrt_amd64.s
@@ -6,7 +6,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !noasm,!appengine
+//+build !noasm,!appengine,!safe
 
 // TODO(kortschak): use textflag.h after we drop Go 1.3 support
 //#include "textflag.h"
diff --git a/mat/offset.go b/mat/offset.go
index 03dd07d9..af2c03b6 100644
--- a/mat/offset.go
+++ b/mat/offset.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !appengine
+// +build !appengine,!safe
 
 package mat
 
diff --git a/mat/offset_appengine.go b/mat/offset_appengine.go
index 16b8f796..df617478 100644
--- a/mat/offset_appengine.go
+++ b/mat/offset_appengine.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build appengine
+// +build appengine safe
 
 package mat