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From: Gunther Vogel <gunther.vogel@gmx.net> To: <gcc-gnats@gcc.gnu.org> Subject: optimization/6019: doubled struct initialization Date: Wed, 20 Mar 2002 09:16:00 -0000 [thread overview] Message-ID: <Pine.LNX.4.33.0203201805140.2667-100000@whiterider.offline> (raw) >Number: 6019 >Category: optimization >Synopsis: doubled struct initialization >Confidential: no >Severity: non-critical >Priority: low >Responsible: unassigned >State: open >Class: pessimizes-code >Submitter-Id: net >Arrival-Date: Wed Mar 20 09:16:02 PST 2002 >Closed-Date: >Last-Modified: >Originator: Gunther Vogel >Release: 3.0.4 >Organization: >Environment: System: Linux whiterider 2.4.17 #10 Tue Feb 26 17:24:09 CET 2002 i686 unknown Architecture: i686 host: i686-pc-linux-gnu build: i686-pc-linux-gnu target: i686-pc-linux-gnu configured with: ./configure --prefix=/usr/src/packages/BUILD/gccgpp-buildroot/usr --mandir=/share/man --with-cpu=athlon --disable-cpp --disable-nls >Description: The first generated movl $2538, ... instructions looks superfluous to me. This effect occurs if and only if optimization (gcc -O[1-3] -S t.c) is used. Using different -march= options (i[3-6]86, athlon) moves things around a bit, but keeps the repetition. (Please take my apology if this is just some kind of subtle optimization I don't comprehend.) >How-To-Repeat: // begin file t.c typedef struct B_ { int b; } B; extern void bar(B*); void foo() { B b = { 2538 }; bar(&b); } // end file t.c // begin excerpt t.s generated by gcc -O2 -S t.c foo: pushl %ebp movl %esp, %ebp subl $20, %esp movl $2538, -4(%ebp) leal -8(%ebp), %eax movl $2538, -8(%ebp) pushl %eax call bar movl %ebp, %esp popl %ebp ret // end excerpt t.s >Fix: unknown >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-03-20 17:16 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-03-20 9:16 Gunther Vogel [this message] 2002-12-06 16:04 bangerth
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