> -----Original Message----- > From: gcc-patches-ow...@gcc.gnu.org [mailto:gcc-patches- > ow...@gcc.gnu.org] On Behalf Of James Greenhalgh > Sent: 02 March 2015 13:28 > To: Maxim Kuvyrkov > Cc: Terry Guo; gcc-patches@gcc.gnu.org; Ramana Radhakrishnan; Richard > Earnshaw > Subject: Re: [PATCH][ARM]Automatically add -mthumb for thumb-only > target when mode isn't specified > > On Mon, Mar 02, 2015 at 01:08:13PM +0000, Maxim Kuvyrkov wrote: > > > On Mar 2, 2015, at 4:44 AM, Terry Guo <terry....@arm.com> wrote: > > > > > > Hi there, > > > > > > If target mode isn't specified via either gcc configuration option > > > --with-mode or command line, this patch intends to improve gcc > > > driver to automatically add option -mthumb for thumb-only target. > > > Tested with gcc regression test for various arm targets, no regression. Is it > OK?
FWIW, I had this annoyance that the patch tries to fix as well and filed a PR for it: PR target/64802 Kyrill > > > > > > BR, > > > Terry > > > > > > gcc/ChangeLog: > > > > > > 2015-03-02 Terry Guo <terry....@arm.com> > > > > > > * common/config/arm/arm-common.c (arm_is_target_thumb_only): > > > New function. > > > * config/arm/arm-protos.h (FL_ Macros): Move to ... > > > * config/arm/arm-opts.h (FL_ Macros): ... here. > > > (struct arm_arch_core_flag): New struct. > > > (arm_arch_core_flags): New array for arch/core and flag map. > > > * config/arm/arm.h (MODE_SET_SPEC_FUNCTIONS): Define new > SPEC > > > function. > > > (EXTRA_SPEC_FUNCTIONS): Include new SPEC function. > > > (MODE_SET_SPECS): New SPEC. > > > (DRIVER_SELF_SPECS): Include new > > > SPEC.<gcc-mthumb-option-v5.txt> > > > > Did you consider approach of implementing this purely inside cc1 rather > than driver? > > > > We do not seem to need to pass -mthumb to assembler or linker since > > those will pick up ARM-ness / Thumb-ness from function annotations. > > Therefore we need to handle -marm / -mthumb for cc1 only. What am I > missing? > > I recently had a similar argument with myself regarding the usefulness of > rewriting -mcpu values in the driver before handing them off the assembler > (as we do for big.LITTLE systems), we could just rely on the .arch directives in > the assembler files. > > The problem with this argument, and the one you make here, is that it > doesn't cover users driving the assembler with a GCC command to assemble > hand-rolled files without directives. i.e. > > gcc foo.s bar.c -mthumb -mcpu=cortex-a57.cortex-a53 > > Should have the effect when assembling foo.s of enforcing thumb mode, > and permitting ARMv8-A instructions, regardless whether foo.s explicitly > enables these through directives. > > Cheers, > James >
