Commit bbf731b3 authored by Johan Almbladh's avatar Johan Almbladh Committed by Daniel Borkmann
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mips, bpf: Optimize loading of 64-bit constants 



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: default avatarJohan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211007142828.634182-1-johan.almbladh@anyfinetworks.com
parent e5c15a36

arch/mips/net/bpf_jit_comp64.c

+7 −1
Original line number Diff line number Diff line
@@ -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);

}