fix(asm): carry the riscv64 scalar pseudos and the swapped branches

Assisted-by: GLM 5.3 Flash

asm/riscv_vecarith_test.go

@@ -810,3 +810,36 @@ TEXT ·vecarith(SB), NOSPLIT, $0
 	}
 	assertRISCVDifferential(t, path, src, "vecarith")
 }
+
+// TestRISCVScalarPseudos_Differential proves the scalar pseudo tail against
+// the toolchain: the NEG/NEGW and SEQZ/SNEZ one- and two-operand forms, the
+// sign-injection pseudos and the two-word not-equal expansions, exactly as
+// the toolchain's own testdata spells them.
+func TestRISCVScalarPseudos_Differential(t *testing.T) {
+	src := `#include "textflag.h"
+
+TEXT ·pseudos(SB), NOSPLIT, $0-8
+	NEG	X5
+	NEG	X5, X6
+	NEGW	X5
+	NEGW	X5, X6
+	SEQZ	X14, X15
+	SNEZ	X14, X15
+	FABSS	F0, F1
+	FNEGS	F0, F1
+	FNES	F0, F1, X7
+	FABSD	F0, F1
+	FNEGD	F0, F1
+	FNED	F0, F1, X5
+	FLTD	F0, F1, X5
+	FLED	F0, F1, X5
+	FEQD	F0, F1, X5
+	RET
+`
+	dir := t.TempDir()
+	path := filepath.Join(dir, "pseudos_riscv64.s")
+	if err := os.WriteFile(path, []byte(src), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	assertRISCVDifferential(t, path, src, "pseudos")
+}