From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 87263 invoked by alias); 8 Jul 2015 20:46:39 -0000 Mailing-List: contact jit-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Post: List-Help: List-Subscribe: Sender: jit-owner@gcc.gnu.org Received: (qmail 87253 invoked by uid 89); 8 Jul 2015 20:46:39 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Checked: by ClamAV 0.98.7 on sourceware.org X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.5 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 X-Spam-Status: No, score=-1.5 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on sourceware.org X-Spam-Level: X-HELO: mail-yk0-f181.google.com X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=xK7XjUmSiZWxOxtKc9tyz55atOku/SpZY92hz2UDiXc=; b=dbEEkReS59bjGWco9aSFlBVkc+g25xbh6QPUlbqKB+Tv8ur3H8xzau6yv8vYpOwSuU zqmiM8sxHi3bJNOQ1Lk127Fhi/nAIn/7j1XNMku3Zflhav7YqstCXzkZZcPQJNVKNZLe SoyKtzFU5aJSApyd2eBqPKj9IdDcf3fQdhuCHA7r4NA1hupTIU2JwHWemWD2dHx8IPVL +inp418MIdLImr0S8P2GKALsxpUFCRiBeHGVJ8qtM6Ma37Ae3hg473gSwRGyo2M6hmzo /42ucHK/Lh47t+24HkV6JuMDiczRX4+JDwHIWywy0YIYdDZfktgOThaZ2j71NZA6XrPd Rzgw== X-Gm-Message-State: ALoCoQnLdZcnc9cfDjq87tlDtwUPPv0kcg72/HUuNccsHf1XWAoAYBlBPJx02JlRfKn0MRzuOeoM MIME-Version: 1.0 X-Received: by 10.170.208.81 with SMTP id z78mr13646177yke.106.1436388395864; Wed, 08 Jul 2015 13:46:35 -0700 (PDT) In-Reply-To: References: <1436365266.24803.65.camel@surprise> <1436367926.24803.71.camel@surprise> <1436369443.24803.75.camel@surprise> <1436377619.24803.97.camel@surprise> Date: Thu, 01 Jan 2015 00:00:00 -0000 Message-ID: Subject: Re: Filed PR jit/66812 for the code generation issue From: Dibyendu Majumdar To: David Malcolm Cc: jit@gcc.gnu.org Content-Type: text/plain; charset=UTF-8 X-SW-Source: 2015-q3/txt/msg00044.txt.bz2 On 8 July 2015 at 21:32, Dibyendu Majumdar wrote: > On 8 July 2015 at 21:22, Dibyendu Majumdar wrote: >> Here is what I think the flow is. >> >> part 1 >> -------- >> >> 1 [2] LOADNIL 0 0 >> >> entry: >> cl = (struct ravi_LClosure *)L->ci->func->value_.gc; >> (void)raviV_op_loadnil (L->ci, (int)0, (int)0); >> >> >> This sets register 0 (local variable IX) to NIL >> >> 2 [3] LOADK 1 -1 ; 10 >> >> (&L->ci->u.l.base[(int)1])->value_.i = (&cl->p->k[(int)0])->value_.i; >> (&L->ci->u.l.base[(int)1])->tt_ = (&cl->p->k[(int)0])->tt_; >> >> This sets the register at 1 (temporary) to 10. >> >> 3 [3] TEST 1 1 >> 4 [3] JMP 0 0 ; to 5 >> >> The above two bytecodes go together. This says that if register 1 is >> true then skip the JMP else JMP. >> So we get: >> >> comparison_0_5 = (&L->ci->u.l.base[(int)1])->tt_ == (int)0; >> comparison_0_6 = (&L->ci->u.l.base[(int)1])->tt_ == (int)1; >> comparison_0_7 = (&L->ci->u.l.base[(int)1])->value_.b == (int)0; >> isfalse_0_4 = comparison_0_5 || comparison_0_6 && comparison_0_7; >> if (!(isfalse_0_4)) goto OP_TEST_do_jmp_2_8; else goto OP_TEST_do_skip_2_9; >> >> The test is checking that register 1 is true (which it is as it has >> the constant 10) - then goto skip_2_9. > > Since we skipped the jump the next instruction is > > 5 [3] LOADBOOL 1 0 0 > > This is setting register 1 to false so we get: > > OP_TEST_do_skip_2_9: > goto jmp_5_1; > > jmp_5_1: > (&L->ci->u.l.base[(int)1])->value_.b = (int)0; > (&L->ci->u.l.base[(int)1])->tt_ = (int)1; > > Next instruction is: > > 6 [3] TEST 1 0 > 7 [3] JMP 0 1 ; to 9 > > Now this is saying that if register is _false_ then skip JMP else JMP. > Since we know that register 1 is false as above then the code should > skip the jump. > > comparison_0_11 = (&L->ci->u.l.base[(int)1])->tt_ == (int)0; > comparison_0_12 = (&L->ci->u.l.base[(int)1])->tt_ == (int)1; > comparison_0_13 = (&L->ci->u.l.base[(int)1])->value_.b == (int)0; > isfalse_0_10 = comparison_0_11 || comparison_0_12 && comparison_0_13; > if (!(!(isfalse_0_10))) goto OP_TEST_do_jmp_5_14; else goto > OP_TEST_do_skip_5_15; > > So we go to skip_5_15: > > 8 [3] LOADBOOL 0 1 0 > > OP_TEST_do_skip_5_15: > (&L->ci->u.l.base[(int)0])->value_.b = (int)1; > (&L->ci->u.l.base[(int)0])->tt_ = (int)1; > goto jmp_9_2; > > So you see that the local IX is set to false above which is what we > want. Next we jump to 9_2 which is the start of the return statement. part 3 ------- Here we essentially have a repeat of what was in entry block: 9 [3] LOADK 1 -1 ; 10 10 [3] TEST 1 1 11 [3] JMP 0 0 ; to 12 jmp_9_2: (&L->ci->u.l.base[(int)1])->value_.i = (&cl->p->k[(int)0])->value_.i; (&L->ci->u.l.base[(int)1])->tt_ = (&cl->p->k[(int)0])->tt_; comparison_0_17 = (&L->ci->u.l.base[(int)1])->tt_ == (int)0; comparison_0_18 = (&L->ci->u.l.base[(int)1])->tt_ == (int)1; comparison_0_19 = (&L->ci->u.l.base[(int)1])->value_.b == (int)0; isfalse_0_16 = comparison_0_17 || comparison_0_18 && comparison_0_19; if (!(isfalse_0_16)) goto OP_TEST_do_jmp_9_20; else goto OP_TEST_do_skip_9_21; So the JMP is not taken as register 1 is _true_ and we go to 9_21: 12 [3] LOADBOOL 1 0 0 OP_TEST_do_skip_9_21: goto jmp_12_3; jmp_12_3: (&L->ci->u.l.base[(int)1])->value_.b = (int)0; (&L->ci->u.l.base[(int)1])->tt_ = (int)1; Above sets the register 1 to false and this is the return value. Next the return instruction begins: L->top = &L->ci->u.l.base[(int)2]; comparison_0_22 = cl->p->sizep > (int)0; if (comparison_0_22) goto OP_RETURN_if_sizep_gt_0_12_23; else goto OP_RETURN_else_sizep_gt_0_12_24; So as far as I can see the generated code is correct and matches the Lua bytecode. Regards Dibyendu