From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22040 invoked by alias); 10 Nov 2010 20:52:49 -0000 Received: (qmail 22026 invoked by uid 22791); 10 Nov 2010 20:52:48 -0000 X-SWARE-Spam-Status: No, hits=-2.8 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 10 Nov 2010 20:52:42 +0000 From: "hubicka at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/38629] target-specific parameters for inline heuristics not defined for AVR X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Keywords: X-Bugzilla-Severity: enhancement X-Bugzilla-Who: hubicka at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Date: Wed, 10 Nov 2010 20:52:00 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2010-11/txt/msg01373.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38629 --- Comment #6 from Jan Hubicka 2010-11-10 20:52:18 UTC --- OK, at -Os the issue is that function is called once so inlining is a win. Making multiple copies of it leads to GCC making clone: delay_wait_us_ms.constprop.0: .LFB3: movl $136, %edi jmp delay_wait_us .LFE3: and then calling it call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 call delay_wait_us_ms.constprop.0 at -Os,that is With -O2 it is different story, we end up inlining everything. We get: Analyzing function body size: delay_wait_us freq: 1000 size: 1 time: 1 __asm__ __volatile__("wdr"); freq: 1000 size: 1 time: 1 MEM[(volatile unsigned char *)82B] ={v} timeout_2(D); freq: 1000 size: 1 time: 1 D.2719_5 ={v} MEM[(volatile unsigned char *)88B]; freq: 1000 size: 1 time: 1 D.2720_6 = D.2719_5 | 1; freq: 1000 size: 1 time: 1 MEM[(volatile unsigned char *)88B] ={v} D.2720_6; freq: 11111 size: 1 time: 1 D.2721_8 ={v} MEM[(volatile unsigned char *)88B]; freq: 11111 size: 0 time: 0 D.2722_9 = (int) D.2721_8; freq: 11111 size: 1 time: 1 D.2723_10 = D.2722_9 & 1; freq: 11111 size: 2 time: 2 if (D.2723_10 == 0) freq: 1000 size: 1 time: 2 return; Likely eliminated Overall function body time: 51-2 size: 10-1 With function call overhead time: 51-13 size: 10-3 that fits in early-inlining-insns. With --param early-inlining-insns=0 we get it right. GCC inliner is guessing here that inlining such a small leaf function will result in enough optimization so it pays back. I am not sure what we can do here, early-inlining-insns is being pushed up by C++ code... It is not terribly bad tradeoff even at -O2. I will try to get some data how much early inlining insns cost us at -O2 and if it is too much, I will disable the allowed growth for functions not declared inline.