diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
index 52246f46..c5b2bc61 100644
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -7,8 +7,8 @@ jobs:
     strategy:
       matrix:
         go:
-        - 1.16
-        - 1.17
+        - 1.17.x
+        - 1.18.x
         os:
         - ubuntu-latest
 
@@ -43,12 +43,9 @@ jobs:
     - name: Setup Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.17.x
+        go-version: 1.18.x
 
-    - name: Generate
-      run: make --always-make build
-
-    - name: Git Status
+    - name: Ensure generated assembler code is up to date
       run: |
-        git diff
-        test -z "$(git status --porcelain)"
+        go install github.com/kevinburke/differ@1.2
+        differ make --always-make build
diff --git a/ascii/equal_fold_amd64.go b/ascii/equal_fold_amd64.go
index 07cf6cdb..117b2297 100644
--- a/ascii/equal_fold_amd64.go
+++ b/ascii/equal_fold_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run equal_fold_asm.go -pkg ascii -out ../ascii/equal_fold_amd64.s -stubs ../ascii/equal_fold_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package ascii
 
diff --git a/ascii/equal_fold_amd64.s b/ascii/equal_fold_amd64.s
index 34495a62..36fc9930 100644
--- a/ascii/equal_fold_amd64.s
+++ b/ascii/equal_fold_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run equal_fold_asm.go -pkg ascii -out ../ascii/equal_fold_amd64.s -stubs ../ascii/equal_fold_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/ascii/valid_amd64.go b/ascii/valid_amd64.go
index 72dc7b43..14d3f64e 100644
--- a/ascii/valid_amd64.go
+++ b/ascii/valid_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run valid_asm.go -pkg ascii -out ../ascii/valid_amd64.s -stubs ../ascii/valid_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package ascii
 
diff --git a/ascii/valid_amd64.s b/ascii/valid_amd64.s
index 0214b0ce..d0dc2355 100644
--- a/ascii/valid_amd64.s
+++ b/ascii/valid_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run valid_asm.go -pkg ascii -out ../ascii/valid_amd64.s -stubs ../ascii/valid_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/ascii/valid_print_amd64.go b/ascii/valid_print_amd64.go
index b1462666..3eef8c5b 100644
--- a/ascii/valid_print_amd64.go
+++ b/ascii/valid_print_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run valid_print_asm.go -pkg ascii -out ../ascii/valid_print_amd64.s -stubs ../ascii/valid_print_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package ascii
 
diff --git a/ascii/valid_print_amd64.s b/ascii/valid_print_amd64.s
index bc2e20a2..8b957294 100644
--- a/ascii/valid_print_amd64.s
+++ b/ascii/valid_print_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run valid_print_asm.go -pkg ascii -out ../ascii/valid_print_amd64.s -stubs ../ascii/valid_print_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/base64/decode_amd64.go b/base64/decode_amd64.go
index 1dae5b43..e85bf6a9 100644
--- a/base64/decode_amd64.go
+++ b/base64/decode_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run decode_asm.go -pkg base64 -out ../base64/decode_amd64.s -stubs ../base64/decode_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package base64
 
diff --git a/base64/decode_amd64.s b/base64/decode_amd64.s
index cc6c779d..ade5442c 100644
--- a/base64/decode_amd64.s
+++ b/base64/decode_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run decode_asm.go -pkg base64 -out ../base64/decode_amd64.s -stubs ../base64/decode_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/base64/encode_amd64.go b/base64/encode_amd64.go
index c38060f7..a83c81f1 100644
--- a/base64/encode_amd64.go
+++ b/base64/encode_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run encode_asm.go -pkg base64 -out ../base64/encode_amd64.s -stubs ../base64/encode_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package base64
 
diff --git a/base64/encode_amd64.s b/base64/encode_amd64.s
index 2edd27aa..6797c977 100644
--- a/base64/encode_amd64.s
+++ b/base64/encode_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run encode_asm.go -pkg base64 -out ../base64/encode_amd64.s -stubs ../base64/encode_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/bswap/swap64_amd64.go b/bswap/swap64_amd64.go
index 04bbb58d..ebbe64ef 100644
--- a/bswap/swap64_amd64.go
+++ b/bswap/swap64_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run swap64_asm.go -pkg bswap -out ../bswap/swap64_amd64.s -stubs ../bswap/swap64_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package bswap
 
diff --git a/bswap/swap64_amd64.s b/bswap/swap64_amd64.s
index 9d6fb5bb..887f5b4a 100644
--- a/bswap/swap64_amd64.s
+++ b/bswap/swap64_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run swap64_asm.go -pkg bswap -out ../bswap/swap64_amd64.s -stubs ../bswap/swap64_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/keyset/keyset_amd64.go b/keyset/keyset_amd64.go
index 9554ee67..0390db71 100644
--- a/keyset/keyset_amd64.go
+++ b/keyset/keyset_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run keyset_asm.go -pkg keyset -out ../keyset/keyset_amd64.s -stubs ../keyset/keyset_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package keyset
 
diff --git a/keyset/keyset_amd64.s b/keyset/keyset_amd64.s
index e27d2c45..cdfbd7f4 100644
--- a/keyset/keyset_amd64.s
+++ b/keyset/keyset_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run keyset_asm.go -pkg keyset -out ../keyset/keyset_amd64.s -stubs ../keyset/keyset_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/mem/blend_amd64.go b/mem/blend_amd64.go
index 0607eadc..845bfb59 100644
--- a/mem/blend_amd64.go
+++ b/mem/blend_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run blend_asm.go -pkg mem -out ../mem/blend_amd64.s -stubs ../mem/blend_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package mem
 
diff --git a/mem/blend_amd64.s b/mem/blend_amd64.s
index 7aa77640..8dfa5620 100644
--- a/mem/blend_amd64.s
+++ b/mem/blend_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run blend_asm.go -pkg mem -out ../mem/blend_amd64.s -stubs ../mem/blend_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/mem/contains_amd64.go b/mem/contains_amd64.go
index ab2d9280..4246db32 100644
--- a/mem/contains_amd64.go
+++ b/mem/contains_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run contains_asm.go -pkg mem -out ../mem/contains_amd64.s -stubs ../mem/contains_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package mem
 
diff --git a/mem/contains_amd64.s b/mem/contains_amd64.s
index 5396a41f..483617b8 100644
--- a/mem/contains_amd64.s
+++ b/mem/contains_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run contains_asm.go -pkg mem -out ../mem/contains_amd64.s -stubs ../mem/contains_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/mem/copy_amd64.go b/mem/copy_amd64.go
index f8393139..856ba92e 100644
--- a/mem/copy_amd64.go
+++ b/mem/copy_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run copy_asm.go -pkg mem -out ../mem/copy_amd64.s -stubs ../mem/copy_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package mem
 
diff --git a/mem/copy_amd64.s b/mem/copy_amd64.s
index e506c5f2..cb5578d5 100644
--- a/mem/copy_amd64.s
+++ b/mem/copy_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run copy_asm.go -pkg mem -out ../mem/copy_amd64.s -stubs ../mem/copy_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/mem/count_pair_amd64.go b/mem/count_pair_amd64.go
index 17f078f7..68af1fe8 100644
--- a/mem/count_pair_amd64.go
+++ b/mem/count_pair_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run count_pair_asm.go -pkg mem -out ../mem/count_pair_amd64.s -stubs ../mem/count_pair_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package mem
 
diff --git a/mem/count_pair_amd64.s b/mem/count_pair_amd64.s
index 924b0263..ab3fd228 100644
--- a/mem/count_pair_amd64.s
+++ b/mem/count_pair_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run count_pair_asm.go -pkg mem -out ../mem/count_pair_amd64.s -stubs ../mem/count_pair_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/mem/index_pair_amd64.go b/mem/index_pair_amd64.go
index 49aa11fd..9807c9db 100644
--- a/mem/index_pair_amd64.go
+++ b/mem/index_pair_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run index_pair_asm.go -pkg mem -out ../mem/index_pair_amd64.s -stubs ../mem/index_pair_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package mem
 
diff --git a/mem/index_pair_amd64.s b/mem/index_pair_amd64.s
index df1b06cd..23c92320 100644
--- a/mem/index_pair_amd64.s
+++ b/mem/index_pair_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run index_pair_asm.go -pkg mem -out ../mem/index_pair_amd64.s -stubs ../mem/index_pair_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/mem/mask_amd64.go b/mem/mask_amd64.go
index 7724eb6c..6a42f917 100644
--- a/mem/mask_amd64.go
+++ b/mem/mask_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run mask_asm.go -pkg mem -out ../mem/mask_amd64.s -stubs ../mem/mask_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package mem
 
diff --git a/mem/mask_amd64.s b/mem/mask_amd64.s
index 3fd32227..438be4bb 100644
--- a/mem/mask_amd64.s
+++ b/mem/mask_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run mask_asm.go -pkg mem -out ../mem/mask_amd64.s -stubs ../mem/mask_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/qsort/sort_amd64.go b/qsort/sort_amd64.go
index bc9bdd60..214d4dde 100644
--- a/qsort/sort_amd64.go
+++ b/qsort/sort_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run sort_asm.go -pkg qsort -out ../qsort/sort_amd64.s -stubs ../qsort/sort_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package qsort
 
diff --git a/qsort/sort_amd64.s b/qsort/sort_amd64.s
index bf67efa8..e745b246 100644
--- a/qsort/sort_amd64.s
+++ b/qsort/sort_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run sort_asm.go -pkg qsort -out ../qsort/sort_amd64.s -stubs ../qsort/sort_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/slices/sums_amd64.go b/slices/sums_amd64.go
index 426df8e9..eabb99de 100644
--- a/slices/sums_amd64.go
+++ b/slices/sums_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run sums_asm.go -pkg slices -out ../slices/sums_amd64.s -stubs ../slices/sums_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package slices
 
diff --git a/slices/sums_amd64.s b/slices/sums_amd64.s
index 8ae09afd..c6e818f0 100644
--- a/slices/sums_amd64.s
+++ b/slices/sums_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run sums_asm.go -pkg slices -out ../slices/sums_amd64.s -stubs ../slices/sums_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/sortedset/dedupe_amd64.go b/sortedset/dedupe_amd64.go
index ab4c7a3b..a9f745e5 100644
--- a/sortedset/dedupe_amd64.go
+++ b/sortedset/dedupe_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run dedupe_asm.go -pkg sortedset -out ../sortedset/dedupe_amd64.s -stubs ../sortedset/dedupe_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package sortedset
 
diff --git a/sortedset/dedupe_amd64.s b/sortedset/dedupe_amd64.s
index 3436013b..2f60fd97 100644
--- a/sortedset/dedupe_amd64.s
+++ b/sortedset/dedupe_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run dedupe_asm.go -pkg sortedset -out ../sortedset/dedupe_amd64.s -stubs ../sortedset/dedupe_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/sortedset/intersect16_amd64.go b/sortedset/intersect16_amd64.go
index cc1a9536..50566de0 100644
--- a/sortedset/intersect16_amd64.go
+++ b/sortedset/intersect16_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run intersect16_asm.go -pkg sortedset -out ../sortedset/intersect16_amd64.s -stubs ../sortedset/intersect16_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package sortedset
 
diff --git a/sortedset/intersect16_amd64.s b/sortedset/intersect16_amd64.s
index 4d05ac0d..80ef026c 100644
--- a/sortedset/intersect16_amd64.s
+++ b/sortedset/intersect16_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run intersect16_asm.go -pkg sortedset -out ../sortedset/intersect16_amd64.s -stubs ../sortedset/intersect16_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/sortedset/union16_amd64.go b/sortedset/union16_amd64.go
index 786b1267..500dad9d 100644
--- a/sortedset/union16_amd64.go
+++ b/sortedset/union16_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run union16_asm.go -pkg sortedset -out ../sortedset/union16_amd64.s -stubs ../sortedset/union16_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package sortedset
 
diff --git a/sortedset/union16_amd64.s b/sortedset/union16_amd64.s
index a5fe041a..71a4152a 100644
--- a/sortedset/union16_amd64.s
+++ b/sortedset/union16_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run union16_asm.go -pkg sortedset -out ../sortedset/union16_amd64.s -stubs ../sortedset/union16_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"
 
diff --git a/utf8/valid_amd64.go b/utf8/valid_amd64.go
index d9e9612d..c18cff67 100644
--- a/utf8/valid_amd64.go
+++ b/utf8/valid_amd64.go
@@ -1,7 +1,6 @@
 // Code generated by command: go run valid_asm.go -pkg utf8 -out ../utf8/valid_amd64.s -stubs ../utf8/valid_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 package utf8
 
diff --git a/utf8/valid_amd64.s b/utf8/valid_amd64.s
index 501dfc62..cf7a3916 100644
--- a/utf8/valid_amd64.s
+++ b/utf8/valid_amd64.s
@@ -1,7 +1,6 @@
 // Code generated by command: go run valid_asm.go -pkg utf8 -out ../utf8/valid_amd64.s -stubs ../utf8/valid_amd64.go. DO NOT EDIT.
 
 //go:build !purego
-// +build !purego
 
 #include "textflag.h"