fix(asm): encode the flag-setting logicals to ZR and fold immediate expressions

Assisted-by: GLM 5.3 Flash

asm/arm64_encode_test.go

@@ -2596,3 +2596,49 @@ func TestArm64VTBLShapes(t *testing.T) {
 		}
 	}
 }
+
+// TestArm64LogicalToZR pins the toolchain's split between the flag-setting
+// logicals, whose ZR destination keeps the bitmask fast path (asm7.go case
+// 53), and the plain forms, which materialise into REGTMP: `go tool asm`
+// encodes ANDSW $0x100, R13, ZR as one TSTW word and ANDW $1, R5, ZR as the
+// ORRW-plus-register pair.
+func TestArm64LogicalToZR(t *testing.T) {
+	got := arm64Words(t, "\tANDSW $0x100, R13, ZR\n\tBICSW $1, R5, ZR\n\tANDSW $0x101, R13, ZR\n\tANDW $1, R5, ZR\n")
+	want := []uint32{
+		0x721801bf, // ANDS (bitmask) R13, ZR: the TSTW word
+		0x721f78bf, // BICS (bitmask of $1) R5, ZR
+		0x5280203b, // MOVW $257, R27: not a bitmask, materialised
+		0x6a1b01bf, // ANDSW R27, R13
+		0x320003fb, // ORRW $1, ZR, R27: the plain form materialises too
+		0x0a1b00bf, // ANDW R27, R5, ZR
+		0xd65f03c0, // RET
+	}
+	if len(got) != len(want) {
+		t.Fatalf("word count = %d, want %d", len(got), len(want))
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Errorf("word %d = %08x, want %08x", i, got[i], want[i])
+		}
+	}
+}
+
+// TestArm64ImmediateExpression pins the folded arithmetic spellings the
+// parser leaves half-parsed: `$14*16` parses as the leading literal 14, and
+// the encoder must read the raw expression's 224 (`go tool asm` folds it).
+func TestArm64ImmediateExpression(t *testing.T) {
+	got := arm64Words(t, "\tADD $14*16, R0\n\tMOVD $4*8+1, R1\n")
+	want := []uint32{
+		0x91038000, // ADD $224, R0
+		0xd2800421, // MOVZ $33, R1: MOVD $con rides MOVZ for a movcon value
+		0xd65f03c0, // RET
+	}
+	if len(got) != len(want) {
+		t.Fatalf("word count = %d, want %d", len(got), len(want))
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Errorf("word %d = %08x, want %08x", i, got[i], want[i])
+		}
+	}
+}