Hi,
Currently when a user compiles for a thumb-only target (such as Cortex-M
processors) without specifying the -mthumb option GCC throws the error "target
CPU does not support ARM mode". This is suboptimal from a usability point of
view: the -mthumb could be deduced from the -march or -mcpu option when there is
no ambiguity.
This patch implements this behavior by extending the DRIVER_SELF_SPECS to
automatically append -mthumb to the command line for thumb-only targets. It does
so by checking the last -march option if any is given or the last -mcpu option
otherwise. There is no ordering issue because conflicting -mcpu and -march is
already handled.
Note that the logic cannot be implemented in function arm_option_override
because we need to provide the modified command line to the GCC driver for
finding the right multilib path and the function arm_option_override is executed
too late for that effect.
ChangeLog entries are as follow:
*** gcc/ChangeLog ***
2016-10-18 Terry Guo <terry....@arm.com>
Thomas Preud'homme <thomas.preudho...@arm.com>
PR target/64802
* common/config/arm/arm-common.c (arm_target_thumb_only): New function.
* config/arm/arm-opts.h: Include arm-flags.h.
(struct arm_arch_core_flag): Define.
(arm_arch_core_flags): Define.
* config/arm/arm-protos.h: Include arm-flags.h.
(FL_NONE, FL_ANY, FL_CO_PROC, FL_ARCH3M, FL_MODE26, FL_MODE32,
FL_ARCH4, FL_ARCH5, FL_THUMB, FL_LDSCHED, FL_STRONG, FL_ARCH5E,
FL_XSCALE, FL_ARCH6, FL_VFPV2, FL_WBUF, FL_ARCH6K, FL_THUMB2, FL_NOTM,
FL_THUMB_DIV, FL_VFPV3, FL_NEON, FL_ARCH7EM, FL_ARCH7, FL_ARM_DIV,
FL_ARCH8, FL_CRC32, FL_SMALLMUL, FL_NO_VOLATILE_CE, FL_IWMMXT,
FL_IWMMXT2, FL_ARCH6KZ, FL2_ARCH8_1, FL2_ARCH8_2, FL2_FP16INST,
FL_TUNE, FL_FOR_ARCH2, FL_FOR_ARCH3, FL_FOR_ARCH3M, FL_FOR_ARCH4,
FL_FOR_ARCH4T, FL_FOR_ARCH5, FL_FOR_ARCH5T, FL_FOR_ARCH5E,
FL_FOR_ARCH5TE, FL_FOR_ARCH5TEJ, FL_FOR_ARCH6, FL_FOR_ARCH6J,
FL_FOR_ARCH6K, FL_FOR_ARCH6Z, FL_FOR_ARCH6ZK, FL_FOR_ARCH6KZ,
FL_FOR_ARCH6T2, FL_FOR_ARCH6M, FL_FOR_ARCH7, FL_FOR_ARCH7A,
FL_FOR_ARCH7VE, FL_FOR_ARCH7R, FL_FOR_ARCH7M, FL_FOR_ARCH7EM,
FL_FOR_ARCH8A, FL2_FOR_ARCH8_1A, FL2_FOR_ARCH8_2A, FL_FOR_ARCH8M_BASE,
FL_FOR_ARCH8M_MAIN, arm_feature_set, ARM_FSET_MAKE,
ARM_FSET_MAKE_CPU1, ARM_FSET_MAKE_CPU2, ARM_FSET_CPU1, ARM_FSET_CPU2,
ARM_FSET_EMPTY, ARM_FSET_ANY, ARM_FSET_HAS_CPU1, ARM_FSET_HAS_CPU2,
ARM_FSET_HAS_CPU, ARM_FSET_ADD_CPU1, ARM_FSET_ADD_CPU2,
ARM_FSET_DEL_CPU1, ARM_FSET_DEL_CPU2, ARM_FSET_UNION, ARM_FSET_INTER,
ARM_FSET_XOR, ARM_FSET_EXCLUDE, ARM_FSET_IS_EMPTY,
ARM_FSET_CPU_SUBSET): Move to ...
* config/arm/arm-flags.h: This new file.
* config/arm/arm.h (TARGET_MODE_SPEC_FUNCTIONS): Define.
(EXTRA_SPEC_FUNCTIONS): Add TARGET_MODE_SPEC_FUNCTIONS to its value.
(TARGET_MODE_SPECS): Define.
(DRIVER_SELF_SPECS): Add TARGET_MODE_SPECS to its value.
*** gcc/testsuite/ChangeLog ***
2016-10-11 Thomas Preud'homme <thomas.preudho...@arm.com>
PR target/64802
* gcc.target/arm/optional_thumb-1.c: New test.
* gcc.target/arm/optional_thumb-2.c: New test.
* gcc.target/arm/optional_thumb-3.c: New test.
No regression when running the testsuite for -mcpu=cortex-m0 -mthumb,
-mcpu=cortex-m0 -marm and -mcpu=cortex-a8 -marm
Is this ok for trunk?
