From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22482 invoked by alias); 8 Jul 2015 20:32:46 -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 22450 invoked by uid 89); 8 Jul 2015 20:32:43 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Checked: by ClamAV 0.98.7 on sourceware.org X-Virus-Found: No X-HELO: mail-yk0-f171.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=C3iOGI3/i3uH7VBddxR1dcJcfQJqC84DVqq5varmmZU=; b=N5vgMpLWrln69v5BTGmkAu5SOiBJ/dYg1hHrs10aSuxhLNtDRyAAQ9bKPiiq47n4CU CaF9BUgtzqjUECJlE5zLXXbQld9mEqu1Nva9gIvLWxIqNKFnItOXhIV6Y/EOJo6YCSKp MhaLu5fyDYG/gvGlEpQ9tOISWYnp6UmHd7CSghpUvFbmuP3z2jlhmVGtAJ9F074F0Z4W f70hTWgw8PEJ0vrRehE21nv3kWGcF95aQsWeIN5uopm9Q755r7kaefk4DV4Ltquq5EF1 QamDOCZXmtCcF2cv1mCNpskTHak7qzn3wPwn2VEBm4rV7UgiJpMLKk3+ci4daOtS+Oz1 xPvg== X-Gm-Message-State: ALoCoQkznr2KbpWHiNYi6brbLG8RjZPXvKjigqTR3tYCgwVzgh2ETpiVkQ2VwteAvJPJE3CvL7Kk MIME-Version: 1.0 X-Received: by 10.129.36.14 with SMTP id k14mr13346948ywk.64.1436387560989; Wed, 08 Jul 2015 13:32:40 -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/msg00043.txt.bz2 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.