| Message ID | 1458335299-27409-3-git-send-email-thomas.petazzoni@free-electrons.com |
|---|---|
| State | Accepted |
| Headers | show |
Thomas, All, On 2016-03-18 22:08 +0100, Thomas Petazzoni spake thusly: > The Cortex-M cores only support Thumb-2, not Thumb. In fact, Thumb-2 > is a superset of Thumb, and we could have a single option for both in > Buildroot, since -mthumb on ARMv4/v5 means original Thumb, while > -mthumb on ARMv7 means Thumb 2. However, for clarity, it makes sense > to have two separate options. But in this case, Cortex-M3 should not > advertise that it supports Thumb, as in fact selecting Thumb would > generate Thumb-2 code. So, if a package has some assembly code written in Thumb not Thimb2, it should do sometinh like: ifeq ($(BR2_ARM_CPU_HAS_THUMB)$(BR2_ARM_CPU_HAS_THUMB2),y) FOO_OPTS += --enable-thumb endif whereas now it would only need to do: ifeq ($(BR2_ARM_CPU_HAS_THUMB)$(BR2_ARM_CPU_HAS_THUMB2),y) FOO_OPTS += --enable-thumb endif Right? > Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Regards, Yann E. MORIN. > --- > arch/Config.in.arm | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/Config.in.arm b/arch/Config.in.arm > index 33f763a..cd1ec33 100644 > --- a/arch/Config.in.arm > +++ b/arch/Config.in.arm > @@ -172,7 +172,6 @@ config BR2_cortex_a17 > select BR2_ARCH_HAS_MMU_OPTIONAL > config BR2_cortex_m3 > bool "cortex-M3" > - select BR2_ARM_CPU_HAS_THUMB > select BR2_ARM_CPU_HAS_THUMB2 > select BR2_ARM_CPU_ARMV7M > config BR2_fa526 > -- > 2.6.4 > > _______________________________________________ > buildroot mailing list > buildroot@busybox.net > http://lists.busybox.net/mailman/listinfo/buildroot
On 03/18/16 23:34, Yann E. MORIN wrote: > Thomas, All, > > On 2016-03-18 22:08 +0100, Thomas Petazzoni spake thusly: >> The Cortex-M cores only support Thumb-2, not Thumb. In fact, Thumb-2 >> is a superset of Thumb, and we could have a single option for both in >> Buildroot, since -mthumb on ARMv4/v5 means original Thumb, while >> -mthumb on ARMv7 means Thumb 2. However, for clarity, it makes sense >> to have two separate options. But in this case, Cortex-M3 should not >> advertise that it supports Thumb, as in fact selecting Thumb would >> generate Thumb-2 code. > > So, if a package has some assembly code written in Thumb not Thimb2, it > should do sometinh like: > > ifeq ($(BR2_ARM_CPU_HAS_THUMB)$(BR2_ARM_CPU_HAS_THUMB2),y) > FOO_OPTS += --enable-thumb > endif > > whereas now it would only need to do: > > ifeq ($(BR2_ARM_CPU_HAS_THUMB)$(BR2_ARM_CPU_HAS_THUMB2),y) I guess you meant to say ifeq ($(BR2_ARM_CPU_HAS_THUMB),y) > FOO_OPTS += --enable-thumb > endif > > Right? Indeed. This was discussed in v1 of the series, and Thomas updated the commit message to clarify that a bit. It turns out that we have no case you need a condition like that, but we do have a few cases where we need thumb-but-not-thumb2 (e.g. the uClibc threads stuff). > >> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> > > Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> Regards, Arnout > > Regards, > Yann E. MORIN. > >> --- >> arch/Config.in.arm | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/arch/Config.in.arm b/arch/Config.in.arm >> index 33f763a..cd1ec33 100644 >> --- a/arch/Config.in.arm >> +++ b/arch/Config.in.arm >> @@ -172,7 +172,6 @@ config BR2_cortex_a17 >> select BR2_ARCH_HAS_MMU_OPTIONAL >> config BR2_cortex_m3 >> bool "cortex-M3" >> - select BR2_ARM_CPU_HAS_THUMB >> select BR2_ARM_CPU_HAS_THUMB2 >> select BR2_ARM_CPU_ARMV7M >> config BR2_fa526 >> -- >> 2.6.4 >> >> _______________________________________________ >> buildroot mailing list >> buildroot@busybox.net >> http://lists.busybox.net/mailman/listinfo/buildroot >
diff --git a/arch/Config.in.arm b/arch/Config.in.arm index 33f763a..cd1ec33 100644 --- a/arch/Config.in.arm +++ b/arch/Config.in.arm @@ -172,7 +172,6 @@ config BR2_cortex_a17 select BR2_ARCH_HAS_MMU_OPTIONAL config BR2_cortex_m3 bool "cortex-M3" - select BR2_ARM_CPU_HAS_THUMB select BR2_ARM_CPU_HAS_THUMB2 select BR2_ARM_CPU_ARMV7M config BR2_fa526
The Cortex-M cores only support Thumb-2, not Thumb. In fact, Thumb-2 is a superset of Thumb, and we could have a single option for both in Buildroot, since -mthumb on ARMv4/v5 means original Thumb, while -mthumb on ARMv7 means Thumb 2. However, for clarity, it makes sense to have two separate options. But in this case, Cortex-M3 should not advertise that it supports Thumb, as in fact selecting Thumb would generate Thumb-2 code. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> --- arch/Config.in.arm | 1 - 1 file changed, 1 deletion(-)