| Message ID | 20170811052847.GA32348@waldemar-brodkorb.de |
|---|---|
| State | Changes Requested |
| Headers | show |
Hello, On Fri, 11 Aug 2017 07:28:48 +0200, Waldemar Brodkorb wrote: > GCC deprecated -mfused-madd, -ffp-contract=off should > be used for Xburst workaround. > uClibc compilations will fail, because a gcc warning > is emitted while checking for TLS support in the compiler. In which gcc version was -ffp-contract=off added ? Can we use that unconditionally, or is it only available in recent gcc versions ? Best regards, Thomas
On 11-08-17 08:08, Thomas Petazzoni wrote: > Hello, > > On Fri, 11 Aug 2017 07:28:48 +0200, Waldemar Brodkorb wrote: >> GCC deprecated -mfused-madd, -ffp-contract=off should >> be used for Xburst workaround. >> uClibc compilations will fail, because a gcc warning >> is emitted while checking for TLS support in the compiler. > > In which gcc version was -ffp-contract=off added ? Can we use that > unconditionally, or is it only available in recent gcc versions ? And remember that we support GCC down to 4.3 in external toolchains... Regards, Arnout
Hi, Thomas Petazzoni wrote, > Hello, > > On Fri, 11 Aug 2017 07:28:48 +0200, Waldemar Brodkorb wrote: > > GCC deprecated -mfused-madd, -ffp-contract=off should > > be used for Xburst workaround. > > uClibc compilations will fail, because a gcc warning > > is emitted while checking for TLS support in the compiler. > > In which gcc version was -ffp-contract=off added ? Can we use that > unconditionally, or is it only available in recent gcc versions ? It was added in commit b9be572eda05cd23bbabd6409387d2c7ac782715. Not sure how to find when it was added in a release. 4.6.4 seems to have it: https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gcc/Optimize-Options.html#index-ffp_002dcontract-691 I don't find it in earlier release docs. best regards Waldemar
Hi Arnout, Arnout Vandecappelle wrote, > > > On 11-08-17 08:08, Thomas Petazzoni wrote: > > Hello, > > > > On Fri, 11 Aug 2017 07:28:48 +0200, Waldemar Brodkorb wrote: > >> GCC deprecated -mfused-madd, -ffp-contract=off should > >> be used for Xburst workaround. > >> uClibc compilations will fail, because a gcc warning > >> is emitted while checking for TLS support in the compiler. > > > > In which gcc version was -ffp-contract=off added ? Can we use that > > unconditionally, or is it only available in recent gcc versions ? > > And remember that we support GCC down to 4.3 in external toolchains... The usage for -ffp-contract=off is limited for MIPS32 xburst and I see only two external toolchains from 2016 for MIPS in make menuconfig... best regards Waldemar
On 11-08-17 20:11, Waldemar Brodkorb wrote: > Hi Arnout, > Arnout Vandecappelle wrote, > >> >> >> On 11-08-17 08:08, Thomas Petazzoni wrote: >>> Hello, >>> >>> On Fri, 11 Aug 2017 07:28:48 +0200, Waldemar Brodkorb wrote: >>>> GCC deprecated -mfused-madd, -ffp-contract=off should >>>> be used for Xburst workaround. >>>> uClibc compilations will fail, because a gcc warning >>>> is emitted while checking for TLS support in the compiler. >>> >>> In which gcc version was -ffp-contract=off added ? Can we use that >>> unconditionally, or is it only available in recent gcc versions ? >> >> And remember that we support GCC down to 4.3 in external toolchains... > > The usage for -ffp-contract=off is limited for MIPS32 xburst and > I see only two external toolchains from 2016 for MIPS in > make menuconfig... There's also something called "Custom external toolchain", which could be anything... Regards, Arnout
On 11-08-17 19:32, Waldemar Brodkorb wrote: > Hi, > Thomas Petazzoni wrote, > >> Hello, >> >> On Fri, 11 Aug 2017 07:28:48 +0200, Waldemar Brodkorb wrote: >>> GCC deprecated -mfused-madd, -ffp-contract=off should >>> be used for Xburst workaround. >>> uClibc compilations will fail, because a gcc warning >>> is emitted while checking for TLS support in the compiler. >> >> In which gcc version was -ffp-contract=off added ? Can we use that >> unconditionally, or is it only available in recent gcc versions ? > > It was added in commit b9be572eda05cd23bbabd6409387d2c7ac782715. > > Not sure how to find when it was added in a release. $ git describe --contains b9be572eda05cd23bbabd6409387d2c7ac782715 gcc-4_6_0-release~2941 So we should use something like: ifeq ($(BR2_TOOLCHAIN_GCC_AT_LEAST_4_6),y) TOOLCHAIN_WRAPPER_ARGS += -DBR_FP_CONTRACT_OFF else TOOLCHAIN_WRAPPER_ARGS += -DBR_NO_FUSED_MADD endif But actually, I'd much prefer this stuff to just be coded in TOOLCHAIN_WRAPPER_OPTS. But that's a much bigger patch (series) so not for master. Regards, Arnout > 4.6.4 seems to have it: > https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gcc/Optimize-Options.html#index-ffp_002dcontract-691 > > I don't find it in earlier release docs. > > best regards > Waldemar > _______________________________________________ > buildroot mailing list > buildroot@busybox.net > http://lists.busybox.net/mailman/listinfo/buildroot >
diff --git a/toolchain/toolchain-wrapper.c b/toolchain/toolchain-wrapper.c index dd77c11..44cdcf3 100644 --- a/toolchain/toolchain-wrapper.c +++ b/toolchain/toolchain-wrapper.c @@ -69,8 +69,8 @@ static char *predef_args[] = { #ifdef BR_OMIT_LOCK_PREFIX "-Wa,-momit-lock-prefix=yes", #endif -#ifdef BR_NO_FUSED_MADD - "-mno-fused-madd", +#ifdef BR_FP_CONTRACT_OFF + "-ffp-contract=off", #endif #ifdef BR_BINFMT_FLAT "-Wl,-elf2flt", diff --git a/toolchain/toolchain-wrapper.mk b/toolchain/toolchain-wrapper.mk index 7f72a0c..ecf67a4 100644 --- a/toolchain/toolchain-wrapper.mk +++ b/toolchain/toolchain-wrapper.mk @@ -27,8 +27,9 @@ TOOLCHAIN_WRAPPER_ARGS += -DBR_OMIT_LOCK_PREFIX endif # Avoid FPU bug on XBurst CPUs +# -mfused-madd is deprecated, use -ffp-contract instead ifeq ($(BR2_mips_xburst),y) -TOOLCHAIN_WRAPPER_ARGS += -DBR_NO_FUSED_MADD +TOOLCHAIN_WRAPPER_ARGS += -DBR_FP_CONTRACT_OFF endif ifeq ($(BR2_CCACHE_USE_BASEDIR),y)
GCC deprecated -mfused-madd, -ffp-contract=off should be used for Xburst workaround. uClibc compilations will fail, because a gcc warning is emitted while checking for TLS support in the compiler. Signed-off-by: Waldemar Brodkorb <wbx@openadk.org> --- toolchain/toolchain-wrapper.c | 4 ++-- toolchain/toolchain-wrapper.mk | 3 ++- 2 files changed, 4 insertions(+), 3 deletions(-)