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From: Matthias Klose <doko@klose.in-berlin.de> To: gcc-gnats@gcc.gnu.org, debian-gcc@lists.debian.org Subject: optimization/3995: i386 optimisation: joining tests Date: Sat, 11 Aug 2001 00:46:00 -0000 [thread overview] Message-ID: <E15VTHM-0001Bc-00@gate.local> (raw) >Number: 3995 >Category: optimization >Synopsis: i386 optimisation: joining tests >Confidential: no >Severity: non-critical >Priority: low >Responsible: unassigned >State: open >Class: sw-bug >Submitter-Id: net >Arrival-Date: Sat Aug 11 00:46:00 PDT 2001 >Closed-Date: >Last-Modified: >Originator: herbert@gondor.apana.org.au >Release: 3.0 (Debian GNU/Linux) >Organization: The Debian project >Environment: System: Debian GNU/Linux (testing/unstable) Architecture: i386 host: i386-linux build: i386-linux target: i386-linux configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux >Description: [ Reported to the Debian BTS as report #105309. Please CC 105309-quiet@bugs.debian.org on replies. Log of report can be found at http://bugs.debian.org/105309 ] Here's another segment that needs to have an assembler optimiser run over it: int foo(char c) { if (c && !(c & 0x80)) { a(); } else { b(); } } produces with -O2: 0: 55 push %ebp 1: 89 e5 mov %esp,%ebp 3: 83 ec 08 sub $0x8,%esp 6: 8a 45 08 mov 0x8(%ebp),%al 9: 84 c0 test %al,%al b: 74 04 je 11 <foo+0x11> d: 84 c0 test %al,%al f: 79 07 jns 18 <foo+0x18> 9-f can be rewritten as: test %al, %al jg 18 11: e8 fc ff ff ff call 12 <foo+0x12> 12: R_386_PC32 b 16: c9 leave 17: c3 ret 18: e8 fc ff ff ff call 19 <foo+0x19> 19: R_386_PC32 a 1d: eb f7 jmp 16 <foo+0x16> And what purpose does this jmp serve? Surely it can be replaced with leave ret 1f: 90 nop >How-To-Repeat: >Fix: >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2001-08-11 0:46 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2001-08-11 0:46 Matthias Klose [this message] 2002-04-02 16:26 rth 2002-05-06 20:40 sayle
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