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From: Richard Henderson <rth@twiddle.net>
To: James Hogan <james.hogan@imgtec.com>
Cc: qemu-devel@nongnu.org, aurelien@aurel32.net
Subject: Re: [Qemu-devel] [PATCH 07/15] tcg-mips: Adjust qemu_ld/st for mips64
Date: Thu, 11 Feb 2016 04:35:48 +1100	[thread overview]
Message-ID: <56BB74F4.5040602@twiddle.net> (raw)
In-Reply-To: <20160210163439.GI3678@jhogan-linux.le.imgtec.org>

On 02/11/2016 03:34 AM, James Hogan wrote:
> Hi Richard,
>
> On Tue, Feb 09, 2016 at 09:39:55PM +1100, Richard Henderson wrote:
>> @@ -1212,11 +1237,24 @@ static void tcg_out_tlb_load(TCGContext *s, TCGReg base, TCGReg addrl,
>>              : offsetof(CPUArchState, tlb_table[mem_index][0].addr_write));
>>       int add_off = offsetof(CPUArchState, tlb_table[mem_index][0].addend);
>>
>> -    tcg_out_opc_sa(s, OPC_SRL, TCG_REG_A0, addrl,
>> -                   TARGET_PAGE_BITS - CPU_TLB_ENTRY_BITS);
>> -    tcg_out_opc_imm(s, OPC_ANDI, TCG_REG_A0, TCG_REG_A0,
>> -                    (CPU_TLB_SIZE - 1) << CPU_TLB_ENTRY_BITS);
>> -    tcg_out_opc_reg(s, OPC_ADDU, TCG_REG_A0, TCG_REG_A0, TCG_AREG0);
>> +    if (use_mips32r2_instructions) {
>> +        if (TCG_TARGET_REG_BITS == 32 || TARGET_LONG_BITS == 32) {
>> +            tcg_out_opc_bf(s, OPC_EXT, TCG_REG_A0, addrl,
>> +                           TARGET_PAGE_BITS + CPU_TLB_ENTRY_BITS - 1,
>> +                           CPU_TLB_ENTRY_BITS);
>> +        } else {
>> +            tcg_out_opc_bf64(s, OPC_DEXT, OPC_DEXTM, OPC_DEXTU,
>> +                             TCG_REG_A0, addrl,
>> +                             TARGET_PAGE_BITS + CPU_TLB_ENTRY_BITS - 1,
>> +                             CPU_TLB_ENTRY_BITS);
>> +        }
>
> The ext/dext here will end up with bits below bit CPU_TLB_ENTRY_BITS
> set, which will result in load of addend from slightly offset address,
> so things go badly wrong. You still need to either ANDI off the low bits
> or trim them off with the ext/dext and shift it left again.
>
> So I don't think there's any benefit to the use of these instructions
> unless CPU_TLB_SIZE + CPU_TLB_ENTRY_BITS exceeds the 16-bits available
> in the ANDI immediate field for the non r2 case.

Hmm.  I thought I'd deleted this code back out.  I must have messed up copying 
trees between machines and overwritten this.


r~

  reply	other threads:[~2016-02-10 17:36 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-09 10:39 [Qemu-devel] [PATCH 00/15] tcg mips64 and mipsr6 improvements Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 01/15] tcg-mips: Add mips64 opcodes Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 02/15] tcg-mips: Support 64-bit opcodes Richard Henderson
2016-02-09 15:24   ` James Hogan
2016-02-09 17:16     ` Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 03/15] tcg-mips: Adjust move functions for mips64 Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 04/15] tcg-mips: Adjust load/store " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 05/15] tcg-mips: Adjust prologue " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 06/15] tcg-mips: Add tcg unwind info Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 07/15] tcg-mips: Adjust qemu_ld/st for mips64 Richard Henderson
2016-02-10 16:34   ` James Hogan
2016-02-10 17:35     ` Richard Henderson [this message]
2016-02-09 10:39 ` [Qemu-devel] [PATCH 08/15] tcg-mips: Adjust calling conventions " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 09/15] tcg-mips: Fix exit_tb " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 10/15] tcg-mips: Move bswap code to subroutines Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 11/15] tcg-mips: Use mips64r6 instructions in tcg_out_movi Richard Henderson
2016-02-09 16:50   ` James Hogan
2016-02-09 17:20     ` Richard Henderson
2016-02-09 17:25     ` Richard Henderson
2016-02-10  0:32     ` James Hogan
2016-02-09 10:40 ` [Qemu-devel] [PATCH 12/15] tcg-mips: Use mips64r6 instructions in tcg_out_ldst Richard Henderson
2016-02-09 10:40 ` [Qemu-devel] [PATCH 13/15] tcg-mips: Use mips64r6 instructions in constant addition Richard Henderson
2016-02-09 10:40 ` [Qemu-devel] [PATCH 14/15] tcg-mips: Use mipsr6 instructions in branches Richard Henderson
2016-02-09 16:22   ` James Hogan
2016-02-09 17:13     ` Richard Henderson
2016-02-09 18:46       ` Maciej W. Rozycki
2016-02-10  0:20     ` James Hogan
2016-02-09 10:40 ` [Qemu-devel] [PATCH 15/15] tcg-mips: Use mipsr6 instructions in calls Richard Henderson
2016-02-10 12:49   ` James Hogan

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