feat(amd64): LOCK and REP prefixes, literal data pseudo-ops and ADJSP

Assisted-by: GLM 5.3 Flash

asm/instrs.go

@@ -65,6 +65,15 @@ var bitTestOp = map[string]int{
 // noOperandTable maps a fixed no-operand mnemonic to its opcode bytes.  The
 // fence names carry their opcode inside the 0F AE /digit group spelled out in
 // full (E8/F0/F8), and PAUSE is F3 90.
+//
+// LOCK, REP and REPN are the prefix statements.  go tool asm encodes each as
+// a standalone one-byte instruction with a PC of its own (F0, F3 and F2
+// respectively), not as a prefix field merged into the next instruction: the
+// statement that follows is encoded unaware of it, and nothing validates
+// that the pairing is a legal one (LOCK before NOP assembles without
+// complaint, each byte pinned against the toolchain).  Because the bytes
+// land in the stream before the following statement anyway, a LOCKed
+// CMPXCHGQ encodes identically to a prefixed form.
 var noOperandTable = map[string][]byte{
 	"CPUID":   {0x0F, 0xA2},
 	"RDTSC":   {0x0F, 0x31},
@@ -78,6 +87,9 @@ var noOperandTable = map[string][]byte{
 	"MFENCE":  {0x0F, 0xAE, 0xF0},
 	"SFENCE":  {0x0F, 0xAE, 0xF8},
 	"UNDEF":   {0x0F, 0x0B},
+	"LOCK":    {0xF0},
+	"REP":     {0xF3},
+	"REPN":    {0xF2},
 }
 
 // --- MOV --------------------------------------------------------------------