From mboxrd@z Thu Jan 1 00:00:00 1970 From: david.jander@protonic.nl (David Jander) Date: Tue, 11 Sep 2012 09:27:53 +0200 Subject: GCC 4.6.x miscompiling arm-linux? In-Reply-To: References: <20120910171654.1d4972b2@archvile> Message-ID: <20120911092753.7b8315d4@archvile> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Matt, On Mon, 10 Sep 2012 18:11:19 +0100 Matthew Leach wrote: > David Jander writes: > > ... > > .text > > .align 2 > > .global flexcan_chip_start > > .type flexcan_chip_start, %function > > flexcan_chip_start: > > @ args = 0, pretend = 0, frame = 0 > > @ frame_needed = 0, uses_anonymous_args = 0 > > @ link register save eliminated. > > mov r3, #0 > > cmp r0, #9 > > str r3, [r1, #0] > > ldrle r3, [r1, #4] > > mov r0, #0 > > str r3, [r1, #4] > > bx lr > > .size flexcan_chip_start, .-flexcan_chip_start > > .ident "GCC: (OSELAS.Toolchain-2011.11.1) 4.6.2" > > .section .note.GNU-stack,"",%progbits > > > > This does indeed look wrong. I had a go at compile your code snippet the > following assembly was produced: > > .text > .align 2 > .global flexcan_chip_start > .type flexcan_chip_start, %function > flexcan_chip_start: > @ Function supports interworking. > @ args = 0, pretend = 0, frame = 0 > @ frame_needed = 0, uses_anonymous_args = 0 > @ link register save eliminated. > cmp r0, #9 > mov r3, #0 > str r3, [r1, #0] > mov r0, #0 > strgt r3, [r1, #4] > bx lr > .size flexcan_chip_start, .-flexcan_chip_start > .ident "GCC: (GNU) 4.3.3" > .section .note.GNU-stack,"",%progbits > > I think this looks correct. Perhaps you could try the angstrom arm5te > toolchain and see if it's a toolchain issue? Yes, this looks a lot better, and is exactly what I get when I compile this code with CodeSourcery GCC-4.4.1 I have tries building gcc-4.6.3 also with OSELAS/PTXdist, and it gives the same (wrong) result as with gcc-4.6.2 > I think this looks correct. Perhaps you could try the angstrom arm5te > toolchain and see if it's a toolchain issue? > > http://www.angstrom-distribution.org/toolchains/angstrom-2011.03-i686-linux-armv5te-linux-gnueabi-toolchain-qte-4.6.3.tar.bz2 This toolchain is a lot older: $ ./usr/local/angstrom/arm/bin/arm-angstrom-linux-gnueabi-gcc --version arm-angstrom-linux-gnueabi-gcc (GCC) 4.3.3 Copyright (C) 2008 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. The tar-ball says 4.6.3, but that is probably the version number of the qte library, not that of gcc, which is 4.3.3, It does indeed produce the same (correct) output as in your case. The newest angstrom (next) toolchain has gcc version 4.5.3, and it produces this (correct) output: flexcan_chip_start: @ Function supports interworking. @ args = 0, pretend = 0, frame = 0 @ frame_needed = 0, uses_anonymous_args = 0 @ link register save eliminated. mov r3, #0 cmp r0, #9 str r3, [r1, #0] mov r0, #0 strgt r3, [r1, #4] bx lr .size flexcan_chip_start, .-flexcan_chip_start .ident "GCC: (GNU) 4.5.3 20110311 (prerelease)" .section .note.GNU-stack,"",%progbits Anyone knows where I can download a pre-built toolchain for 32-bit linux that is based on gcc-4.6 and/or gcc-4.7 to try out? I have quite a hard time believing this issue is a yet unknown bug in GCC... I'd rather believe that I lack sufficient GCC knowledge to know how to correctly tell the compiler that this is a memory-IO operation. Anyone knows how to do this correctly? Or to explain why the output of gcc-4.6 looks less optimal than the output of older versions of GCC? Best regards, -- David Jander Protonic Holland.