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Re: toolchain/45673: gcc on i386 current generates bad code for assembler code in lock.h
The following reply was made to PR toolchain/45673; it has been noted by GNATS.
From: "Kai-Uwe Eckhardt" <kuehro%gmx.de@localhost>
Subject: Re: toolchain/45673: gcc on i386 current generates bad code for
assembler code in lock.h
Date: Sun, 11 Mar 2012 10:06:54 +0100
it looks like a problem in the toolchain. The gcc in 6.0_BETA and current
i386 is built with --with-march=i486 --with-tune=nocona. Nocona has the
64 bit registers available and this leads to wrong code. It also
fails on amd64 using -m32 where -mtune=nocana is default as well.
Running the test case with -m32 -march=i486 -mtune=pentiumpro works fine.
I propose fixing x86/lock.h on i386 and amd64 by using q for the register
usage directive. Using nocona as default tuning in i386 should be
reconsidered. I suggest pentiumpro which is a good default value for
all processors in my experience.
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