[RFC bpf-next 1/2] bpf, mips: Factor register moves into helpers

[Nicholas Dudar]

Both MIPS JITs currently lower register MOV instructions directly in
build_insn(), duplicating backend-specific handling for ALU32 and ALU64
destinations.

Introduce 32-bit and 64-bit register-move helpers in each backend and
route the existing MOV paths through them. Keep the verifier-inserted
zero-extension marker on its dedicated path, so this is a
behavior-preserving refactor.

Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Nicholas Dudar <main.kalliope@xxxxxxxxx>
---
 arch/mips/net/bpf_jit_comp32.c | 22 ++++++++++++++++++----
 arch/mips/net/bpf_jit_comp64.c | 18 +++++++++++++++---
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/arch/mips/net/bpf_jit_comp32.c b/arch/mips/net/bpf_jit_comp32.c
index 40a878b672f5d..bfe73b023983e 100644
--- a/arch/mips/net/bpf_jit_comp32.c
+++ b/arch/mips/net/bpf_jit_comp32.c
@@ -190,6 +190,22 @@ static void emit_zext_ver(struct jit_context *ctx, const u8 dst[])
 	}
 }
 
+/* Register move operation (32-bit) */
+static void emit_mov_r32(struct jit_context *ctx, const u8 dst[],
+			 const u8 src[])
+{
+	emit_mov_r(ctx, lo(dst), lo(src));
+	emit_zext_ver(ctx, dst);
+}
+
+/* Register move operation (64-bit) */
+static void emit_mov_r64(struct jit_context *ctx, const u8 dst[],
+			 const u8 src[])
+{
+	emit_mov_r(ctx, lo(dst), lo(src));
+	emit_mov_r(ctx, hi(dst), hi(src));
+}
+
 /* Load delay slot, if ISA mandates it */
 static void emit_load_delay(struct jit_context *ctx)
 {
@@ -1485,8 +1501,7 @@ int build_insn(const struct bpf_insn *insn, struct jit_context *ctx)
 			/* Special mov32 for zext */
 			emit_mov_i(ctx, hi(dst), 0);
 		} else {
-			emit_mov_r(ctx, lo(dst), lo(src));
-			emit_zext_ver(ctx, dst);
+			emit_mov_r32(ctx, dst, src);
 		}
 		break;
 	/* dst = -dst */
@@ -1555,8 +1570,7 @@ int build_insn(const struct bpf_insn *insn, struct jit_context *ctx)
 		break;
 	/* dst = src (64-bit) */
 	case BPF_ALU64 | BPF_MOV | BPF_X:
-		emit_mov_r(ctx, lo(dst), lo(src));
-		emit_mov_r(ctx, hi(dst), hi(src));
+		emit_mov_r64(ctx, dst, src);
 		break;
 	/* dst = -dst (64-bit) */
 	case BPF_ALU64 | BPF_NEG:
diff --git a/arch/mips/net/bpf_jit_comp64.c b/arch/mips/net/bpf_jit_comp64.c
index fa7e9aa37f498..45fee6f6b87e9 100644
--- a/arch/mips/net/bpf_jit_comp64.c
+++ b/arch/mips/net/bpf_jit_comp64.c
@@ -120,6 +120,19 @@ static void emit_zext_ver(struct jit_context *ctx, u8 dst)
 		emit_zext(ctx, dst);
 }
 
+/* Register move operation (32-bit) */
+static void emit_mov_r32(struct jit_context *ctx, u8 dst, u8 src)
+{
+	emit_mov_r(ctx, dst, src);
+	emit_zext_ver(ctx, dst);
+}
+
+/* Register move operation (64-bit) */
+static void emit_mov_r64(struct jit_context *ctx, u8 dst, u8 src)
+{
+	emit_mov_r(ctx, dst, src);
+}
+
 /* dst = imm (64-bit) */
 static void emit_mov_i64(struct jit_context *ctx, u8 dst, u64 imm64)
 {
@@ -656,8 +669,7 @@ int build_insn(const struct bpf_insn *insn, struct jit_context *ctx)
 			/* Special mov32 for zext */
 			emit_zext(ctx, dst);
 		} else {
-			emit_mov_r(ctx, dst, src);
-			emit_zext_ver(ctx, dst);
+			emit_mov_r32(ctx, dst, src);
 		}
 		break;
 	/* dst = -dst */
@@ -742,7 +754,7 @@ int build_insn(const struct bpf_insn *insn, struct jit_context *ctx)
 		break;
 	/* dst = src (64-bit) */
 	case BPF_ALU64 | BPF_MOV | BPF_X:
-		emit_mov_r(ctx, dst, src);
+		emit_mov_r64(ctx, dst, src);
 		break;
 	/* dst = -dst (64-bit) */
 	case BPF_ALU64 | BPF_NEG: