[PATCH bpf-next] mips, bpf: Optimize loading of 64-bit constants
From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Date: 2021-10-07 14:28:43
Also in:
bpf
Subsystem:
bpf jit for mips (32-bit and 64-bit), bpf [general] (safe dynamic programs and tools), mips, the rest · Maintainers:
Johan Almbladh, Paul Burton, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Thomas Bogendoerfer, Linus Torvalds
This patch shaves off a few instructions when loading sparse 64-bit constants to register. The change is covered by additional tests in lib/test_bpf.c. Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com> --- arch/mips/net/bpf_jit_comp64.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/mips/net/bpf_jit_comp64.c b/arch/mips/net/bpf_jit_comp64.c
index 1f1f7b87f213..815ade724227 100644
--- a/arch/mips/net/bpf_jit_comp64.c
+++ b/arch/mips/net/bpf_jit_comp64.c@@ -131,19 +131,25 @@ static void emit_mov_i64(struct jit_context *ctx, u8 dst, u64 imm64) emit(ctx, ori, dst, dst, (u16)imm64 & 0xffff); } else { u8 acc = MIPS_R_ZERO; + int shift = 0; int k; for (k = 0; k < 4; k++) { u16 half = imm64 >> (48 - 16 * k); if (acc == dst) - emit(ctx, dsll, dst, dst, 16); + shift += 16; if (half) { + if (shift) + emit(ctx, dsll_safe, dst, dst, shift); emit(ctx, ori, dst, acc, half); acc = dst; + shift = 0; } } + if (shift) + emit(ctx, dsll_safe, dst, dst, shift); } clobber_reg(ctx, dst); }
--
2.30.2