feat(asm): assemble the extended instruction layer on amd64

Assisted-by: GLM 5.3 Flash

asm/assemble.go

@@ -8,6 +8,7 @@ import (
 	"strconv"
 	"strings"
 
+	"sourcedock.dev/petrbalvin/gasm-sdk/arch"
 	"sourcedock.dev/petrbalvin/gasm-sdk/ast"
 )
 
@@ -929,6 +930,25 @@ func encodeInstr(s *ast.Instr, pc int, offsets map[string]int, fi frameInfo, lon
 
 func encodeNormal(s *ast.Instr, fi frameInfo, link *linkInfo) ([]byte, []sbPatch, []floatPoolEntry, error) {
 	mnemUpper := strings.ToUpper(s.Mnemonic.Text)
+
+	// The extended-instruction layer: a statement whose mnemonic is
+	// registered in the extension registry and that the scalar paths cannot
+	// encode goes through the registry, before operandFromAST would reject
+	// operands only the layer reads (asm/amd64_ext.go).  The registry's
+	// Feature field stays metadata at assembly time: the assembler has no
+	// CPU, and the toolchain does not gate assembly on CPU features, so
+	// every registered feature assembles.
+	if extops, pinned, convErr := amd64ExtStatement(mnemUpper, s.Operands); pinned {
+		if convErr != nil {
+			return nil, nil, nil, convErr
+		}
+		code, encErr := EncodeExtension(arch.AMD64, mnemUpper, extops...)
+		if encErr != nil {
+			return nil, nil, nil, encErr
+		}
+		return code, nil, nil, nil
+	}
+
 	if mnemUpper == "FUNCDATA" || mnemUpper == "PCDATA" {
 		code, err := encodeBookkeeping(mnemUpper, s)
 		if err != nil {