diff --git a/internal/inst/table.go b/internal/inst/table.go
new file mode 100644
index 0000000..532de80
--- /dev/null
+++ b/internal/inst/table.go
@@ -0,0 +1,12 @@
+package inst
+
+//go:generate avogen -data ../data -output ztable.go godata
+
+func Lookup(opcode string) (Instruction, bool) {
+	for _, i := range Instructions {
+		if i.Opcode == opcode {
+			return i, true
+		}
+	}
+	return Instruction{}, false
+}
diff --git a/internal/inst/inst_test.go b/internal/inst/table_test.go
similarity index 61%
rename from internal/inst/inst_test.go
rename to internal/inst/table_test.go
index e9d1a35..6659c30 100644
--- a/internal/inst/inst_test.go
+++ b/internal/inst/table_test.go
@@ -1,6 +1,8 @@
 package inst_test
 
 import (
+	"io/ioutil"
+	"strings"
 	"testing"
 
 	"github.com/mmcloughlin/avo/internal/gen"
@@ -49,3 +51,27 @@ func TestAssembles(t *testing.T) {
 	}
 	test.Assembles(t, b)
 }
+
+func TestLookup(t *testing.T) {
+	if _, found := inst.Lookup("CPUID"); !found {
+		t.Fatalf("missing CPUID")
+	}
+	if _, found := inst.Lookup(strings.Repeat("XXX", 13)); found {
+		t.Fatalf("lookup returns true on an absurd opcode")
+	}
+}
+
+func TestStdLibOpcodes(t *testing.T) {
+	t.Skip("currently does not pass")
+
+	b, err := ioutil.ReadFile("testdata/stdlibopcodes.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	opcodes := strings.Fields(string(b))
+	for _, opcode := range opcodes {
+		if _, found := inst.Lookup(opcode); !found {
+			t.Errorf("missing instruction %s (used in stdlib asm)", opcode)
+		}
+	}
+}
diff --git a/internal/inst/testdata/stdlibopcodes.txt b/internal/inst/testdata/stdlibopcodes.txt
new file mode 100644
index 0000000..bfc2c2b
--- /dev/null
+++ b/internal/inst/testdata/stdlibopcodes.txt
@@ -0,0 +1,202 @@
+ADCQ
+ADCXQ
+ADDB
+ADDL
+ADDQ
+ADDSD
+ADOXQ
+AESDEC
+AESDECLAST
+AESENC
+AESENCLAST
+AESIMC
+AESKEYGENASSIST
+ANDB
+ANDL
+ANDNPD
+ANDPD
+ANDQ
+BSFL
+BSFQ
+BSRQ
+BSWAPL
+BSWAPQ
+BTQ
+BYTE
+CALL
+CMOVQCC
+CMOVQCS
+CMOVQEQ
+CMOVQGT
+CMOVQLT
+CMOVQNE
+CMPB
+CMPL
+CMPQ
+CMPSD
+CMPW
+CMPXCHGL
+CMPXCHGQ
+COMISD
+CRC32B
+CRC32L
+CRC32Q
+CRC32W
+CVTSD2SL
+CVTSL2SD
+CVTSQ2SD
+CVTTSD2SQ
+DECB
+DECQ
+DIVL
+DIVQ
+DIVSD
+FUNCDATA
+IMUL3Q
+IMULQ
+INCB
+INCQ
+INT
+JA
+JAE
+JB
+JBE
+JC
+JCC
+JE
+JEQ
+JG
+JGE
+JGT
+JHI
+JL
+JLE
+JLS
+JLT
+JMP
+JNC
+JNE
+JNZ
+JZ
+LDMXCSR
+LEAL
+LEAQ
+MAXSD
+MINSD
+MOVAPD
+MOVAPS
+MOVB
+MOVBLZX
+MOVBQZX
+MOVD
+MOVL
+MOVLQSX
+MOVLQZX
+MOVO
+MOVOA
+MOVOU
+MOVQ
+MOVSD
+MOVUPS
+MOVW
+MULL
+MULQ
+MULSD
+MULXQ
+NEGQ
+NOTL
+NOTQ
+ORB
+ORL
+ORPD
+ORQ
+PADDD
+PADDL
+PAND
+PANDN
+PCLMULQDQ
+PCMPEQB
+PCMPEQL
+PCMPESTRI
+PEXTRB
+PEXTRD
+PINSRB
+PINSRD
+PINSRQ
+PINSRW
+PMOVMSKB
+POPCNTL
+POPQ
+PREFETCHNTA
+PSHUFB
+PSHUFD
+PSHUFHW
+PSHUFL
+PSLLDQ
+PSLLL
+PSLLQ
+PSRAL
+PSRLDQ
+PSRLL
+PSRLQ
+PSUBL
+PUNPCKLBW
+PUSHQ
+PXOR
+RCRQ
+RORXL
+RORXQ
+SALQ
+SARQ
+SBBQ
+SETEQ
+SETGT
+SETHI
+SHLL
+SHLQ
+SHRL
+SHRQ
+SHUFPS
+SQRTSD
+STMXCSR
+SUBL
+SUBQ
+SUBSD
+TESTB
+TESTL
+TESTQ
+TESTW
+VADDSD
+VFMADD213SD
+VFNMADD231SD
+VMOVDQA
+VMOVDQU
+VMOVNTDQ
+VPADDD
+VPADDQ
+VPALIGNR
+VPAND
+VPBLENDD
+VPBROADCASTB
+VPCMPEQB
+VPERM2F128
+VPERM2I128
+VPMOVMSKB
+VPOR
+VPSHUFB
+VPSHUFD
+VPSLLD
+VPSLLQ
+VPSRLD
+VPSRLDQ
+VPSRLQ
+VPTEST
+VPXOR
+XADDL
+XADDQ
+XCHGL
+XCHGQ
+XORB
+XORL
+XORPS
+XORQ
diff --git a/script/stdlibopcodes b/script/stdlibopcodes
new file mode 100755
index 0000000..df8147f
--- /dev/null
+++ b/script/stdlibopcodes
@@ -0,0 +1,22 @@
+#!/bin/bash -e
+
+eval $(go env)
+
+workdir=$(mktemp -d)
+
+# Provide stub "go_asm.h".
+include=${workdir}/include
+mkdir -p ${include}
+echo '#define get_tls ' > ${include}/go_asm.h
+
+# Preprocess all assembly files.
+asm=${workdir}/all.s
+find ${GOROOT}/src -name '*_amd64.s' | while read s; do
+  gcc -E -I${GOROOT}/pkg/include -I${include} ${s} >>${asm}
+done
+
+# Extract instructions.
+awk '/^[[:space:]]+[A-Z0-9]+[[:space:]]+/ { print $1 }' ${asm} | sort | uniq
+
+# Clean.
+rm -rf ${workdir}