From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 124334 invoked by alias); 8 Jul 2015 21:04:20 -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 124318 invoked by uid 89); 8 Jul 2015 21:04:19 -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-f179.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=b16zHYx84go3liiIpfJVjDwDYyvfXAf7/DTtZNN/OI0=; b=bC8FRNpqn3IL9gjjyPAc4jdcAwt0S77HJGybfcZ9y2z9q18T9LqjTcAmXWbO+UxYvd /kJIkg9BPag2HkEdq96YUizEqpItBX44/F6Cc6f1XZcwac8Pi/c4gK8sw/EGYR084qNP 59qAnnqrsw5SXf5VMmvkfnmfbSKQJxbSYTzyAs0NhqEqdiiqgf+Ce6PNASR18Llxmz04 Gwj0jFwEdBXF3WWHky0naoFhrEhrmbVuDpV5kcsWFLqT2QqGgEM0uxsUy3nxtTXazhem vcq55M8A6O8CWUL33FkDam1icHAE6z9S561dXDFwj3WSjpBdHBlNaf2k/JSq3a7gCAl8 MTrA== X-Gm-Message-State: ALoCoQkw2/m39smXvIYA6vs0MJ1jIPH5zU+dUBnBTVhK+qAqa7zp+D4I6ecSKAGwoP94m279Bt/5 MIME-Version: 1.0 X-Received: by 10.129.27.6 with SMTP id b6mr13264692ywb.134.1436389456362; Wed, 08 Jul 2015 14:04:16 -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/msg00045.txt.bz2 On 8 July 2015 at 21:46, Dibyendu Majumdar wrote: > 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. > Having said that ... I have doubts now. Let me check this again. Regards