Re: Patch for 4.7: Avoid subreg'ing VFP D registers in big-endian mode
2013-02-20 Seth LaForge set...@google.com Backport 2012-10-22 Julian Brown jul...@codesourcery.com * config/arm/arm.h (CANNOT_CHANGE_MODE_CLASS): Avoid subreg'ing VFP D registers in big-endian mode. Applied to the 4.7 branch after QEMU-testing for arm-eabi in big-endian mode. It also fixes a fair number of execution failures in the testsuite. -- Eric Botcazou
Re: Patch for 4.7: Avoid subreg'ing VFP D registers in big-endian mode
On Tue, Feb 19, 2013 at 2:59 PM, Ramana Radhakrishnan ramana@googlemail.com wrote: This is not the correct form of a changelog entry. Sorry - another attempt below. Ok to backport provided no regressions when running the testsuite in big endian mode. Sorry to say I'm not sure how to run the testsuite, given that I'm cross-compiling for a wacky TI automotive microcontroller. I'm out of town for the next few days, but I can try to run it under qemu next week. Watch out for alignment of the \'s though it might be your mailer munging things rather than anything else. Can you please make sure that the \'s are aligned to the same column please ? This is why I prefer to get git to generate out patches using git-format-patch and attach them as text files to all my mails otherwise it seems to mess things up like this. They're aligned for me, and I successfully applied my patch by copying it out of my mail, so I blame your mail client. :) In any case, git patch attached. Seth Hopefully correct changelog entry: 2013-02-20 Seth LaForge set...@google.com Backport 2012-10-22 Julian Brown jul...@codesourcery.com * config/arm/arm.h (CANNOT_CHANGE_MODE_CLASS): Avoid subreg'ing VFP D registers in big-endian mode. 0001-Avoid-subreg-ing-VFP-D-registers-in-big-endian-mode.patch Description: Binary data
Re: Patch for 4.7: Avoid subreg'ing VFP D registers in big-endian mode
On Fri, Feb 15, 2013 at 10:40 PM, Seth LaForge set...@google.com wrote: gcc 4.7.2 generates incorrect code for big-endian ARM VFP processors when storing a local double to a packed memory location, as described in bug 56351. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56351 A fix has been submitted to the trunk by Julian Brown: http://gcc.gnu.org/git/?p=gcc.git;a=patch;h=4f0e4afcb2a9d345ed7e9c14233fb97d3a3e8d3c This fix is not included in the latest 4.7 snapshot. Can we please include it in the 4.7 branch so that this serious codegen bug is fixed in 4.7.3? Unfortunately, it's a not a trivial backport, as it appears that support for ARM FPA floating point has been removed from gcc since 4.7. Below is my best attempt at a backport - it works for me, on a big-endian VFP processor. I'm not familiar with this code, though - Julian, can you take a look and confirm whether I'm doing this right? 2013-02-15 Seth LaForge set...@google.com * config/arm/arm.h (CANNOT_CHANGE_MODE_CLASS): Avoid subreg'ing VFP D registers in big-endian mode. Backported from a change by Julian Brown jul...@codesourcery.com This is not the correct form of a changelog entry . Please see other examples of Backports in the Changelog file for the 4.7 branch. Instead please use something like this. DATE yourname youremailid TABBackport TAB2012-10-22 Julian Brown jul...@codesourcery.com * config/arm/arm.h (CANNOT_CHANGE_MODE_CLASS): Avoid subreg'ing VFP D registers in big-endian mode. Ok to backport provided no regressions when running the testsuite in big endian mode. diff -urp gcc-4.7.2/gcc/config/arm/arm.h gcc-4.7.2.new/gcc/config/arm/arm.h --- gcc-4.7.2/gcc/config/arm/arm.h 2012-01-09 20:14:09.0 -0800 +++ gcc-4.7.2.new/gcc/config/arm/arm.h 2013-02-15 14:03:09.113531299 -0800 @@ -1123,11 +1123,18 @@ enum reg_class /* FPA registers can't do subreg as all values are reformatted to internal precision. In VFPv1, VFP registers could only be accessed in the mode they were set, so subregs would be invalid there too. However, we don't - support VFPv1 at the moment, and the restriction was lifted in VFPv2. */ + support VFPv1 at the moment, and the restriction was lifted in VFPv2. + In big-endian mode, modes greater than word size (i.e. DFmode) are stored in + VFP registers in little-endian order. We can't describe that accurately to + GCC, so avoid taking subregs of such values. */ #define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ - (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ - ? reg_classes_intersect_p (FPA_REGS, (CLASS)) \ - : 0) + (TARGET_VFP \ + ? TARGET_BIG_END \ + (GET_MODE_SIZE (FROM) UNITS_PER_WORD \ + || GET_MODE_SIZE (TO) UNITS_PER_WORD) \ + reg_classes_intersect_p (VFP_REGS, (CLASS)) \ + : GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ + reg_classes_intersect_p (FPA_REGS, (CLASS))) Watch out for alignment of the \'s though it might be your mailer munging things rather than anything else. Can you please make sure that the \'s are aligned to the same column please ? This is why I prefer to get git to generate out patches using git-format-patch and attach them as text files to all my mails otherwise it seems to mess things up like this. Thanks, Ramana
Patch for 4.7: Avoid subreg'ing VFP D registers in big-endian mode
gcc 4.7.2 generates incorrect code for big-endian ARM VFP processors when storing a local double to a packed memory location, as described in bug 56351. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56351 A fix has been submitted to the trunk by Julian Brown: http://gcc.gnu.org/git/?p=gcc.git;a=patch;h=4f0e4afcb2a9d345ed7e9c14233fb97d3a3e8d3c This fix is not included in the latest 4.7 snapshot. Can we please include it in the 4.7 branch so that this serious codegen bug is fixed in 4.7.3? Unfortunately, it's a not a trivial backport, as it appears that support for ARM FPA floating point has been removed from gcc since 4.7. Below is my best attempt at a backport - it works for me, on a big-endian VFP processor. I'm not familiar with this code, though - Julian, can you take a look and confirm whether I'm doing this right? 2013-02-15 Seth LaForge set...@google.com * config/arm/arm.h (CANNOT_CHANGE_MODE_CLASS): Avoid subreg'ing VFP D registers in big-endian mode. Backported from a change by Julian Brown jul...@codesourcery.com diff -urp gcc-4.7.2/gcc/config/arm/arm.h gcc-4.7.2.new/gcc/config/arm/arm.h --- gcc-4.7.2/gcc/config/arm/arm.h 2012-01-09 20:14:09.0 -0800 +++ gcc-4.7.2.new/gcc/config/arm/arm.h 2013-02-15 14:03:09.113531299 -0800 @@ -1123,11 +1123,18 @@ enum reg_class /* FPA registers can't do subreg as all values are reformatted to internal precision. In VFPv1, VFP registers could only be accessed in the mode they were set, so subregs would be invalid there too. However, we don't - support VFPv1 at the moment, and the restriction was lifted in VFPv2. */ + support VFPv1 at the moment, and the restriction was lifted in VFPv2. + In big-endian mode, modes greater than word size (i.e. DFmode) are stored in + VFP registers in little-endian order. We can't describe that accurately to + GCC, so avoid taking subregs of such values. */ #define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ - (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ - ? reg_classes_intersect_p (FPA_REGS, (CLASS)) \ - : 0) + (TARGET_VFP \ + ? TARGET_BIG_END \ + (GET_MODE_SIZE (FROM) UNITS_PER_WORD \ + || GET_MODE_SIZE (TO) UNITS_PER_WORD) \ + reg_classes_intersect_p (VFP_REGS, (CLASS)) \ + : GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ + reg_classes_intersect_p (FPA_REGS, (CLASS))) /* The class value for index registers, and the one for base regs. */ #define INDEX_REG_CLASS (TARGET_THUMB1 ? LO_REGS : GENERAL_REGS)
