From: Aurelien Jarno <aurelien@aurel32.net>
To: Blue Swirl <blauwirbel@gmail.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v2 13/19] target-mips: implement unaligned loads using TCG
Date: Tue, 30 Oct 2012 21:00:28 +0100 [thread overview]
Message-ID: <20121030200028.GA22710@hall.aurel32.net> (raw)
In-Reply-To: <CAAu8pHtm4Q6AaytMR6zEstf6dpxuHfzorrjVGE-TJZW1emARqQ@mail.gmail.com>
On Tue, Oct 30, 2012 at 06:59:36PM +0000, Blue Swirl wrote:
> On Tue, Oct 30, 2012 at 12:12 AM, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > Load/store from helpers should be avoided as they are quite
> > inefficient. Rewrite unaligned loads instructions using TCG and
> > aligned loads. The number of actual loads operations to implement
> > an unaligned load instruction is reduced from up to 8 to 1.
>
> There are still other ops around the load operation. How about
> implementing unaligned accesses at TCG level, then targets like x86
> which don't care about alignment can implement them with normal
> accesses more efficiently?
Well maybe the name "unaligned load instructions is misleading". These
instructions actually do not do any unaligned access, instead they
merge the value from memory in the left (LWL, LDL) or right (LWR, LDR)
part of the register, the number of merged bytes depends on the actual
alignemnt of the address. That way a combination of LWL + LWR or LDL +
LDR instructions provide an effective unaligned access. That's why there
are still ops around the actually load, for merging the value in the
register.
If you want to reduce the number of ops around the load, the way to go
is to add a deposit op that take registers for ofs and len. Not sure
it's worthwhile here.
> >
> > Note: As we can't rely on shift by 32 or 64 undefined behaviour,
> > the code loads already shift by one constants.
> >
> > Reviewed-by: Richard Henderson <rth@twiddle.net>
> > Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> > ---
> > target-mips/helper.h | 4 --
> > target-mips/op_helper.c | 142 -----------------------------------------------
> > target-mips/translate.c | 75 ++++++++++++++++++++-----
> > 3 files changed, 62 insertions(+), 159 deletions(-)
> >
> > diff --git a/target-mips/helper.h b/target-mips/helper.h
> > index 210960f..0e38cdd 100644
> > --- a/target-mips/helper.h
> > +++ b/target-mips/helper.h
> > @@ -4,13 +4,9 @@ DEF_HELPER_3(raise_exception_err, noreturn, env, i32, int)
> > DEF_HELPER_2(raise_exception, noreturn, env, i32)
> >
> > #ifdef TARGET_MIPS64
> > -DEF_HELPER_4(ldl, tl, env, tl, tl, int)
> > -DEF_HELPER_4(ldr, tl, env, tl, tl, int)
> > DEF_HELPER_4(sdl, void, env, tl, tl, int)
> > DEF_HELPER_4(sdr, void, env, tl, tl, int)
> > #endif
> > -DEF_HELPER_4(lwl, tl, env, tl, tl, int)
> > -DEF_HELPER_4(lwr, tl, env, tl, tl, int)
> > DEF_HELPER_4(swl, void, env, tl, tl, int)
> > DEF_HELPER_4(swr, void, env, tl, tl, int)
> >
> > diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
> > index 78497d9..773c710 100644
> > --- a/target-mips/op_helper.c
> > +++ b/target-mips/op_helper.c
> > @@ -350,56 +350,6 @@ HELPER_ST_ATOMIC(scd, ld, sd, 0x7)
> > #define GET_OFFSET(addr, offset) (addr - (offset))
> > #endif
> >
> > -target_ulong helper_lwl(CPUMIPSState *env, target_ulong arg1,
> > - target_ulong arg2, int mem_idx)
> > -{
> > - target_ulong tmp;
> > -
> > - tmp = do_lbu(env, arg2, mem_idx);
> > - arg1 = (arg1 & 0x00FFFFFF) | (tmp << 24);
> > -
> > - if (GET_LMASK(arg2) <= 2) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 1), mem_idx);
> > - arg1 = (arg1 & 0xFF00FFFF) | (tmp << 16);
> > - }
> > -
> > - if (GET_LMASK(arg2) <= 1) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 2), mem_idx);
> > - arg1 = (arg1 & 0xFFFF00FF) | (tmp << 8);
> > - }
> > -
> > - if (GET_LMASK(arg2) == 0) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 3), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFF00) | tmp;
> > - }
> > - return (int32_t)arg1;
> > -}
> > -
> > -target_ulong helper_lwr(CPUMIPSState *env, target_ulong arg1,
> > - target_ulong arg2, int mem_idx)
> > -{
> > - target_ulong tmp;
> > -
> > - tmp = do_lbu(env, arg2, mem_idx);
> > - arg1 = (arg1 & 0xFFFFFF00) | tmp;
> > -
> > - if (GET_LMASK(arg2) >= 1) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -1), mem_idx);
> > - arg1 = (arg1 & 0xFFFF00FF) | (tmp << 8);
> > - }
> > -
> > - if (GET_LMASK(arg2) >= 2) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -2), mem_idx);
> > - arg1 = (arg1 & 0xFF00FFFF) | (tmp << 16);
> > - }
> > -
> > - if (GET_LMASK(arg2) == 3) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -3), mem_idx);
> > - arg1 = (arg1 & 0x00FFFFFF) | (tmp << 24);
> > - }
> > - return (int32_t)arg1;
> > -}
> > -
> > void helper_swl(CPUMIPSState *env, target_ulong arg1, target_ulong arg2,
> > int mem_idx)
> > {
> > @@ -440,98 +390,6 @@ void helper_swr(CPUMIPSState *env, target_ulong arg1, target_ulong arg2,
> > #define GET_LMASK64(v) (((v) & 7) ^ 7)
> > #endif
> >
> > -target_ulong helper_ldl(CPUMIPSState *env, target_ulong arg1,
> > - target_ulong arg2, int mem_idx)
> > -{
> > - uint64_t tmp;
> > -
> > - tmp = do_lbu(env, arg2, mem_idx);
> > - arg1 = (arg1 & 0x00FFFFFFFFFFFFFFULL) | (tmp << 56);
> > -
> > - if (GET_LMASK64(arg2) <= 6) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 1), mem_idx);
> > - arg1 = (arg1 & 0xFF00FFFFFFFFFFFFULL) | (tmp << 48);
> > - }
> > -
> > - if (GET_LMASK64(arg2) <= 5) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 2), mem_idx);
> > - arg1 = (arg1 & 0xFFFF00FFFFFFFFFFULL) | (tmp << 40);
> > - }
> > -
> > - if (GET_LMASK64(arg2) <= 4) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 3), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFF00FFFFFFFFULL) | (tmp << 32);
> > - }
> > -
> > - if (GET_LMASK64(arg2) <= 3) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 4), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFF00FFFFFFULL) | (tmp << 24);
> > - }
> > -
> > - if (GET_LMASK64(arg2) <= 2) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 5), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFFFF00FFFFULL) | (tmp << 16);
> > - }
> > -
> > - if (GET_LMASK64(arg2) <= 1) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 6), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFFFFFF00FFULL) | (tmp << 8);
> > - }
> > -
> > - if (GET_LMASK64(arg2) == 0) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, 7), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFFFFFFFF00ULL) | tmp;
> > - }
> > -
> > - return arg1;
> > -}
> > -
> > -target_ulong helper_ldr(CPUMIPSState *env, target_ulong arg1,
> > - target_ulong arg2, int mem_idx)
> > -{
> > - uint64_t tmp;
> > -
> > - tmp = do_lbu(env, arg2, mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFFFFFFFF00ULL) | tmp;
> > -
> > - if (GET_LMASK64(arg2) >= 1) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -1), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFFFFFF00FFULL) | (tmp << 8);
> > - }
> > -
> > - if (GET_LMASK64(arg2) >= 2) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -2), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFFFF00FFFFULL) | (tmp << 16);
> > - }
> > -
> > - if (GET_LMASK64(arg2) >= 3) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -3), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFFFF00FFFFFFULL) | (tmp << 24);
> > - }
> > -
> > - if (GET_LMASK64(arg2) >= 4) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -4), mem_idx);
> > - arg1 = (arg1 & 0xFFFFFF00FFFFFFFFULL) | (tmp << 32);
> > - }
> > -
> > - if (GET_LMASK64(arg2) >= 5) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -5), mem_idx);
> > - arg1 = (arg1 & 0xFFFF00FFFFFFFFFFULL) | (tmp << 40);
> > - }
> > -
> > - if (GET_LMASK64(arg2) >= 6) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -6), mem_idx);
> > - arg1 = (arg1 & 0xFF00FFFFFFFFFFFFULL) | (tmp << 48);
> > - }
> > -
> > - if (GET_LMASK64(arg2) == 7) {
> > - tmp = do_lbu(env, GET_OFFSET(arg2, -7), mem_idx);
> > - arg1 = (arg1 & 0x00FFFFFFFFFFFFFFULL) | (tmp << 56);
> > - }
> > -
> > - return arg1;
> > -}
> > -
> > void helper_sdl(CPUMIPSState *env, target_ulong arg1, target_ulong arg2,
> > int mem_idx)
> > {
> > diff --git a/target-mips/translate.c b/target-mips/translate.c
> > index c46129d..b385923 100644
> > --- a/target-mips/translate.c
> > +++ b/target-mips/translate.c
> > @@ -1125,7 +1125,7 @@ static void gen_ld (CPUMIPSState *env, DisasContext *ctx, uint32_t opc,
> > int rt, int base, int16_t offset)
> > {
> > const char *opn = "ld";
> > - TCGv t0, t1;
> > + TCGv t0, t1, t2;
> >
> > if (rt == 0 && env->insn_flags & (INSN_LOONGSON2E | INSN_LOONGSON2F)) {
> > /* Loongson CPU uses a load to zero register for prefetch.
> > @@ -1157,21 +1157,45 @@ static void gen_ld (CPUMIPSState *env, DisasContext *ctx, uint32_t opc,
> > opn = "lld";
> > break;
> > case OPC_LDL:
> > - save_cpu_state(ctx, 1);
> > t1 = tcg_temp_new();
> > + tcg_gen_andi_tl(t1, t0, 7);
> > +#ifndef TARGET_WORDS_BIGENDIAN
> > + tcg_gen_xori_tl(t1, t1, 7);
> > +#endif
> > + tcg_gen_shli_tl(t1, t1, 3);
> > + tcg_gen_andi_tl(t0, t0, ~7);
> > + tcg_gen_qemu_ld64(t0, t0, ctx->mem_idx);
> > + tcg_gen_shl_tl(t0, t0, t1);
> > + tcg_gen_xori_tl(t1, t1, 63);
> > + t2 = tcg_const_tl(0x7fffffffffffffffull);
> > + tcg_gen_shr_tl(t2, t2, t1);
> > gen_load_gpr(t1, rt);
> > - gen_helper_1e2i(ldl, t1, t1, t0, ctx->mem_idx);
> > - gen_store_gpr(t1, rt);
> > + tcg_gen_and_tl(t1, t1, t2);
> > + tcg_temp_free(t2);
> > + tcg_gen_or_tl(t0, t0, t1);
> > tcg_temp_free(t1);
> > + gen_store_gpr(t0, rt);
> > opn = "ldl";
> > break;
> > case OPC_LDR:
> > - save_cpu_state(ctx, 1);
> > t1 = tcg_temp_new();
> > + tcg_gen_andi_tl(t1, t0, 7);
> > +#ifdef TARGET_WORDS_BIGENDIAN
> > + tcg_gen_xori_tl(t1, t1, 7);
> > +#endif
> > + tcg_gen_shli_tl(t1, t1, 3);
> > + tcg_gen_andi_tl(t0, t0, ~7);
> > + tcg_gen_qemu_ld64(t0, t0, ctx->mem_idx);
> > + tcg_gen_shr_tl(t0, t0, t1);
> > + tcg_gen_xori_tl(t1, t1, 63);
> > + t2 = tcg_const_tl(0xfffffffffffffffeull);
> > + tcg_gen_shl_tl(t2, t2, t1);
> > gen_load_gpr(t1, rt);
> > - gen_helper_1e2i(ldr, t1, t1, t0, ctx->mem_idx);
> > - gen_store_gpr(t1, rt);
> > + tcg_gen_and_tl(t1, t1, t2);
> > + tcg_temp_free(t2);
> > + tcg_gen_or_tl(t0, t0, t1);
> > tcg_temp_free(t1);
> > + gen_store_gpr(t0, rt);
> > opn = "ldr";
> > break;
> > case OPC_LDPC:
> > @@ -1217,21 +1241,46 @@ static void gen_ld (CPUMIPSState *env, DisasContext *ctx, uint32_t opc,
> > opn = "lbu";
> > break;
> > case OPC_LWL:
> > - save_cpu_state(ctx, 1);
> > t1 = tcg_temp_new();
> > + tcg_gen_andi_tl(t1, t0, 3);
> > +#ifndef TARGET_WORDS_BIGENDIAN
> > + tcg_gen_xori_tl(t1, t1, 3);
> > +#endif
> > + tcg_gen_shli_tl(t1, t1, 3);
> > + tcg_gen_andi_tl(t0, t0, ~3);
> > + tcg_gen_qemu_ld32u(t0, t0, ctx->mem_idx);
> > + tcg_gen_shl_tl(t0, t0, t1);
> > + tcg_gen_xori_tl(t1, t1, 31);
> > + t2 = tcg_const_tl(0x7fffffffull);
> > + tcg_gen_shr_tl(t2, t2, t1);
> > gen_load_gpr(t1, rt);
> > - gen_helper_1e2i(lwl, t1, t1, t0, ctx->mem_idx);
> > - gen_store_gpr(t1, rt);
> > + tcg_gen_and_tl(t1, t1, t2);
> > + tcg_temp_free(t2);
> > + tcg_gen_or_tl(t0, t0, t1);
> > tcg_temp_free(t1);
> > + tcg_gen_ext32s_tl(t0, t0);
> > + gen_store_gpr(t0, rt);
> > opn = "lwl";
> > break;
> > case OPC_LWR:
> > - save_cpu_state(ctx, 1);
> > t1 = tcg_temp_new();
> > + tcg_gen_andi_tl(t1, t0, 3);
> > +#ifdef TARGET_WORDS_BIGENDIAN
> > + tcg_gen_xori_tl(t1, t1, 3);
> > +#endif
> > + tcg_gen_shli_tl(t1, t1, 3);
> > + tcg_gen_andi_tl(t0, t0, ~3);
> > + tcg_gen_qemu_ld32u(t0, t0, ctx->mem_idx);
> > + tcg_gen_shr_tl(t0, t0, t1);
> > + tcg_gen_xori_tl(t1, t1, 31);
> > + t2 = tcg_const_tl(0xfffffffeull);
> > + tcg_gen_shl_tl(t2, t2, t1);
> > gen_load_gpr(t1, rt);
> > - gen_helper_1e2i(lwr, t1, t1, t0, ctx->mem_idx);
> > - gen_store_gpr(t1, rt);
> > + tcg_gen_and_tl(t1, t1, t2);
> > + tcg_temp_free(t2);
> > + tcg_gen_or_tl(t0, t0, t1);
> > tcg_temp_free(t1);
> > + gen_store_gpr(t0, rt);
> > opn = "lwr";
> > break;
> > case OPC_LL:
> > --
> > 1.7.10.4
> >
> >
>
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
next prev parent reply other threads:[~2012-10-30 20:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-30 0:11 [Qemu-devel] [PATCH v2 00/19] target-mips: misc fixes and optimizations Aurelien Jarno
2012-10-30 0:11 ` [Qemu-devel] [PATCH v2 01/19] target-mips: correctly restore btarget upon exception Aurelien Jarno
2012-10-30 0:11 ` [Qemu-devel] [PATCH v2 02/19] target-mips: do not save CPU state when using retranslation Aurelien Jarno
2012-10-30 0:11 ` [Qemu-devel] [PATCH v2 03/19] softfloat: implement fused multiply-add NaN propagation for MIPS Aurelien Jarno
2012-10-30 0:11 ` [Qemu-devel] [PATCH v2 04/19] target-mips: use the softfloat floatXX_muladd functions Aurelien Jarno
2012-10-30 0:11 ` [Qemu-devel] [PATCH v2 05/19] target-mips: keep softfloat exception set to 0 between instructions Aurelien Jarno
2012-10-30 0:11 ` [Qemu-devel] [PATCH v2 06/19] target-mips: fix FPU exceptions Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 07/19] target-mips: cleanup float to int conversion helpers Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 08/19] target-mips: use softfloat constants when possible Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 09/19] target-mips: restore CPU state after an FPU exception Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 10/19] target-mips: cleanup load/store operations Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 11/19] target-mips: optimize load operations Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 12/19] target-mips: simplify load/store microMIPS helpers Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 13/19] target-mips: implement unaligned loads using TCG Aurelien Jarno
2012-10-30 18:59 ` Blue Swirl
2012-10-30 20:00 ` Aurelien Jarno [this message]
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 14/19] target-mips: don't use local temps for store conditional Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 15/19] target-mips: implement movn/movz using movcond Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 16/19] target-mips: optimize ddiv/ddivu/div/divu with movcond Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 17/19] target-mips: use deposit instead of hardcoded version Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 18/19] target-mips: fix TLBR wrt SEGMask Aurelien Jarno
2012-10-30 0:12 ` [Qemu-devel] [PATCH v2 19/19] target-mips: don't flush extra TLB on permissions upgrade Aurelien Jarno
2012-10-31 6:37 ` [Qemu-devel] [PATCH v2 00/19] target-mips: misc fixes and optimizations Richard Henderson
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