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powerpc/bpf/32: Optimise some particular const operations

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Simplify multiplications and divisions with constants when the
constant is 1 or -1.

When the constant is a power of 2, replace them by bit shits.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e53b1f4a4150ec6cabcaeeef82bf9c361b5f9204.1675245773.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2023-02-01 11:04:29 +01:00 committed by Michael Ellerman
parent d3921cbb6c
commit 8616045fe7
1 changed files with 20 additions and 3 deletions
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23
arch/powerpc/net/bpf_jit_comp32.c
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@ -391,7 +391,13 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
EMIT(PPC_RAW_MULW(dst_reg, dst_reg, src_reg));
break;
case BPF_ALU | BPF_MUL | BPF_K: /* (u32) dst *= (u32) imm */
if (imm >= -32768 && imm < 32768) {
if (imm == 1)
break;
if (imm == -1) {
EMIT(PPC_RAW_SUBFIC(dst_reg, dst_reg, 0));
} else if (is_power_of_2((u32)imm)) {
EMIT(PPC_RAW_SLWI(dst_reg, dst_reg, ilog2(imm)));
} else if (imm >= -32768 && imm < 32768) {
EMIT(PPC_RAW_MULI(dst_reg, dst_reg, imm));
} else {
PPC_LI32(_R0, imm);
@ -411,6 +417,13 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
EMIT(PPC_RAW_SUBFZE(dst_reg_h, dst_reg_h));
break;
}
if (imm > 0 && is_power_of_2(imm)) {
imm = ilog2(imm);
EMIT(PPC_RAW_RLWINM(dst_reg_h, dst_reg_h, imm, 0, 31 - imm));
EMIT(PPC_RAW_RLWIMI(dst_reg_h, dst_reg, imm, 32 - imm, 31));
EMIT(PPC_RAW_SLWI(dst_reg, dst_reg, imm));
break;
}
bpf_set_seen_register(ctx, tmp_reg);
PPC_LI32(tmp_reg, imm);
EMIT(PPC_RAW_MULW(dst_reg_h, dst_reg_h, tmp_reg));
@ -438,8 +451,12 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
if (imm == 1)
break;
PPC_LI32(_R0, imm);
EMIT(PPC_RAW_DIVWU(dst_reg, dst_reg, _R0));
if (is_power_of_2((u32)imm)) {
EMIT(PPC_RAW_SRWI(dst_reg, dst_reg, ilog2(imm)));
} else {
PPC_LI32(_R0, imm);
EMIT(PPC_RAW_DIVWU(dst_reg, dst_reg, _R0));
}
break;
case BPF_ALU | BPF_MOD | BPF_K: /* (u32) dst %= (u32) imm */
if (!imm)