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From: | Richard Henderson |
Subject: | Re: [PATCH v3] target/xtensa: clean up unaligned access |
Date: | Tue, 18 May 2021 15:11:32 -0500 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 |
On 5/17/21 3:52 PM, Max Filippov wrote:
-static void gen_load_store_alignment(DisasContext *dc, int shift, - TCGv_i32 addr, bool no_hw_alignment) +static MemOp gen_load_store_alignment(DisasContext *dc, int shift, + TCGv_i32 addr, bool no_hw_alignment) { if (!option_enabled(dc, XTENSA_OPTION_UNALIGNED_EXCEPTION)) { tcg_gen_andi_i32(addr, addr, ~0 << shift); - } else if (option_enabled(dc, XTENSA_OPTION_HW_ALIGNMENT) && - no_hw_alignment) { - TCGLabel *label = gen_new_label(); - TCGv_i32 tmp = tcg_temp_new_i32(); - tcg_gen_andi_i32(tmp, addr, ~(~0 << shift)); - tcg_gen_brcondi_i32(TCG_COND_EQ, tmp, 0, label); - gen_exception_cause_vaddr(dc, LOAD_STORE_ALIGNMENT_CAUSE, addr); - gen_set_label(label); - tcg_temp_free(tmp); + } + if (!no_hw_alignment && option_enabled(dc, XTENSA_OPTION_HW_ALIGNMENT)) { + return MO_UNALN; + } else { + return MO_ALIGN; } }@@ -1784,10 +1770,11 @@ static void translate_l32e(DisasContext *dc, const OpcodeArg arg[],const uint32_t par[]) { TCGv_i32 addr = tcg_temp_new_i32(); + MemOp al;tcg_gen_addi_i32(addr, arg[1].in, arg[2].imm);- gen_load_store_alignment(dc, 2, addr, false); - tcg_gen_qemu_ld_tl(arg[0].out, addr, dc->ring, MO_TEUL); + al = gen_load_store_alignment(dc, 2, addr, false); + tcg_gen_qemu_ld_tl(arg[0].out, addr, dc->ring, MO_TEUL | al);
You're duplicating the information about the size of the alignment.I think it would be better to pass the partial MemOp into get_load_store_alignment and return the complete MemOp. E.g.:
MemOp gen_load_store_alignment(DisasContext *dc, MemOp mop, TCGv addr) { if ((mop & MO_SIZE) == MO_8) { return mop; } if ((mop & MO_AMASK) == 0 && !option_enabled(dc, XTENSA_OPTION_HW_ALIGNMENT)) { mop |= MO_ALIGN; } if (!option_enabled(dc, XTENSA_OPTION_UNALIGNED_EXCEPTION)) { tcg_gen_andi_i32(addr, addr, ~0 << get_alignment_bits(mop)); } return mop; } Then used as mop = gen_load_store_alignment(dc, MO_TEUL, addr); tcg_gen_qemu_ld_tl(arg[0].out, addr, dc->ring, mop); mop = gen_load_store_alignment(dc, MO_TEUL | MO_ALIGN, addr); gen_check_exclusive(dc, addr, false); tcg_gen_qemu_ld_i32(arg[0].out, addr, dc->ring, mop);This organization does require that you remove TARGET_ALIGNED_ONLY=y from default-configs/targets/xtensa*.mak so that MO_ALIGN has the non-zero value.
r~
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