Tracking issues with 1.0 and GNU/LLVM toolchain

[nashif]

The series zephyrproject-rtos/zephyr#94360 contains a set of SDK 1.0 compatibility patches. This is ready for review and merging.

• arch/x86 zefi build script fixes for picolibc as default C library.
• intel_adsp fails to build with GCC 14.3.
• adc_stm32 fails to build.
• cmsis-dsp module needs to use C library stdint.h for GCC 14.3.
• Add compiler_barrier in CODE_UNREACHABLE to avoid code deletion.
• ARM64 interrupt test failures. arch.interrupt and arch.shared_interrupt.
• ARM test failures. mps3/corstone300/an547 in arch.arm.pxn_without_userspace, arch.arm.pxn_with_userspace. GCC is inlining an explicitly labeled 'noinline' function.
• RX fails scheduler timeslice tests by a tiny amount. Increase the allowed error a bit.

SDK 1.0 builds -O2 and -Os versions of each library and startup file. This demonstrates the areas needing work, @tejlmand is working on a better solution, but this could be merged as a stop-gap measure.

• Need to pass optimization flags to linker. SDK 1.0 linker compatibility fixes zephyr#94359

Modules ready, only pending west update. These are ready for review and merging.

• rpi_pico using newlib for boot_stage2.modules/hal_rpi_pico: Switch boot_stage2 to picolibc zephyr#94355
• cmsis_6 depending on newlib. modules/cmsis_6: Move to version with picolibc patch zephyr#94356
• silabs hal fails to build with GCC 14.3. west: Update silabs hal for both cmsis-6 and cmsis-5 compatibility zephyr#93895
• cmsis-dsp elicits some possibly undefined var warnings from GCC 14.3. west: Add cmsis-dsp fix for gcc 14.3 zephyr#94361

Modules with outstanding PRs. These need module review and merging and then Zephyr review and merging.

• TFM picolibc support. Use picolibc instead of newlib-nano trusted-firmware-m#134 modules: Update trusted-firmware-m for picolibc zephyr#94367
• PSA tests fail with GCC 14.3. Add 'volatile' to all cmsdk device registers psa-arch-tests#14 modules/psa-arch-tests: Add pending GCC 14.3 support patch zephyr#94357
• mbedtls module fails to build with GCC 14.3. Avoid invalid gcc 14.3 warning about array bounds in mbedtls_xor mbedtls#73 west: Add mbedtls fix for gcc 14.3 zephyr#94358
• ARM test failure in libraries.cmsis_dsp.filtering.biquad.fpu. cmsis_dsp is doing an invalid right shift by a negative value. arm_biquad_cascade_df1_32x64_q31: asrl(val, -shift) -> lsll(val, shift) cmsis-dsp#7 west: Add cmsis-dsp fix for shifting by negative amounts zephyr#94362

Finished issues

• GCC 14.3 RISC-V -Os compilation bug. No longer occurs in testing with linked PRs. Could have been caused by code deletion in paths marked 'unreachable'?

Current architecture pass status with the two PRs listed above

• arc
• arm
• arm64
• mips
• posix. Not relevant as this uses the host compiler.
• riscv
• sparc
• xtensa
• x86
• rx. Currently skips the C library tests.

[keith-packard]

arm64 interrupt test failures have been figured out -- it's gcc using SIMD registers as a part of va_start that is used in printk. Interrupts end up disabled after that, making nested interrupts fail. A patch for this is part of zephyrproject-rtos/zephyr#93042.