feat(arch): add the {1toN} broadcast to the packed amd64 memory sources

Assisted-by: GLM 5.3 Flash

arch/amd64_ext_mem_test.go

@@ -76,6 +76,8 @@ func TestAmd64ExtMemoryRejects(t *testing.T) {
 			"arrangement"},
 		{"predicate qualifier on the memory operand", ExtOperand{Kind: ExtMem, Reg: 8, Qual: ExtQualZeroing},
 			"predicate qualifier"},
+		{"broadcast on an entry that takes none", ExtBroadcast(8, 0),
+			"takes none"},
 	} {
 		_, _, err := in.amd64Memory(tt.op, 1)
 		if err == nil {
@@ -86,6 +88,57 @@ func TestAmd64ExtMemoryRejects(t *testing.T) {
 			t.Errorf("%s: error %q lacks %q", tt.name, err, tt.quote)
 		}
 	}
+	// The broadcast spelling passes the flag gate on an entry that carries
+	// Bcast and then meets the same base and displacement checks.
+	bcast := ExtInstr{Name: "TEST", Bcast: true}
+	for _, tt := range []struct {
+		name  string
+		op    ExtOperand
+		quote string
+	}{
+		{"broadcast base beyond r15", ExtOperand{Kind: ExtMem, Reg: 16, Imm: 0, Broadcast: true},
+			"outside 0-15"},
+		{"broadcast displacement past the signed 32-bit ceiling", ExtBroadcast(8, 1<<31),
+			"outside the signed 32-bit range"},
+		{"broadcast base under r0", ExtBroadcast(-1, 0),
+			"outside 0-15"},
+	} {
+		if _, _, err := bcast.amd64Memory(tt.op, 1); err == nil {
+			t.Errorf("%s: validation succeeded, want an error", tt.name)
+		} else if !strings.Contains(err.Error(), tt.quote) {
+			t.Errorf("%s: error %q lacks %q", tt.name, err, tt.quote)
+		}
+	}
+}
+
+// TestAmd64ExtBroadcastEncoding pins the broadcast layer over the memory
+// encoding: EVEX.b, bit 4 of byte three, set on the VADDPH 512-bit template
+// while the ModR/M mod bits, the SIB byte and the displacement choices keep
+// the plain semantics amd64EncodeMemory chooses.
+func TestAmd64ExtBroadcastEncoding(t *testing.T) {
+	add := []byte{0x62, 0x05, 0x04, 0x40, 0x58, 0xC0}
+	for _, tt := range []struct {
+		name string
+		base int
+		disp int64
+		want string
+	}{
+		{"zero displacement keeps the mod-00 form under the broadcast bit", 9, 0,
+			"624514505831"},
+		{"disp8 semantics unchanged", 1, 127,
+			"6265145058717f"},
+		{"disp32 semantics unchanged", 2, 8128,
+			"6265145058b2c01f0000"},
+		{"RBP keeps the forced displacement", 5, 0,
+			"62651450587500"},
+		{"RSP keeps the SIB byte", 12, 0,
+			"62451450583424"},
+	} {
+		got := amd64EncodeBroadcast(add, 30, 29, tt.base, tt.disp)
+		if hex.EncodeToString(got) != tt.want {
+			t.Errorf("%s:\n  got  %x\n  want %s", tt.name, got, tt.want)
+		}
+	}
 }
 
 // TestAmd64ExtMemoryVocabulary pins the names the shared layer gives the