Revert "toolchain: gcc: Simplify `GEN_ABSOLUTE_SYM` and `GEN_ABSOLUTE_SYM_KCONFIG`"
This reverts commit87779e73f8. Commit87779e73f8("toolchain: gcc: Simplify GEN_ABSOLUTE_SYM and GEN_ABSOLUTE_SYM_KCONFIG") "unified the variants from using a target-specific dialects to a target-agnostic solution". While reducing duplication is always desired, this "unification" got rid of some differences between architectures. Among others, this commit generalized the use of the `c` constant operand modifier in the `GEN_ABSOLUTE_SYM()` macro. Before this commit, the `c` modifier was NOT in use in a number of architectures! Generally speaking, reducing copy/paste/diverge must always be performed in _two_ distinct phases with ample testing time between the two phases: 1. First, perform functional changes that remove the divergence. < give plenty enough time for testing > 2. Finally, remove the identical copies. More specifically, I understand the `c` modifier may be required by some architectures, but it's causing problems on other(s). Notably, it broke the build with one pre-C11, gcc-based Xtensa toolchain: ``` 14:03:17 kernel_offsets.h: Assembler messages: 14:03:17 kernel_offsets.h:28: Error: bad expression 14:03:17 kernel_offsets.h:28: Error: junk at end of line, first unrecognized character is `c' 14:03:17 kernel_offsets.h:29: Error: bad expression 14:03:17 kernel_offsets.h:29: Error: junk at end of line, first unrecognized character is `c' ... ``` While newer Xtensa toolchains accept `c`, they also ignore it. `c` makes no difference whatsoever with all the (working) Xtensa toolchains I tested. So for `Xtensa`, `c` is a best useless and at worse breaking the build. Up to gcc version 12 (2022), the `c` constant modifier was documented as X86-specific! https://gcc.gnu.org/onlinedocs/gcc-12.3.0/gcc/Extended-Asm.html#x86Operandmodifiers Only starting with gcc version 13 (2023), the `c` modifier was officially supported as "generic": https://gcc.gnu.org/onlinedocs/gcc-13.1.0/gcc/Extended-Asm.html#Generic-Operand-Modifiers `c` was very likely working with other architectures before 2023, but not officially and we don't know which architectures and we don't know when. Note toolchain/gcc.h is included by toolchain/llvm.h and also used by clang. The status of `c` across clang versions is unknown. While I personally hate copy/paste/diverge with a passion, these macros GEN_ABSOLUTE_SYM() and GEN_ABSOLUTE_SYM_KCONFIG() are very small so that particular duplication is very reasonable. Architecture-specific code is tricky and portability across toolchain and toolchain versions even more. Testing low-level changes like this across different architectures would also require demanding and unlikely coordination across different architectures/companies. Signed-off-by: Marc Herbert <marc.herbert@intel.com>
This commit is contained in:
Marc Herbert
Anas Nashif
parent
51d80a9838
commit
89493ee56b
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@ -489,52 +489,85 @@ do { \
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* to generate named symbol/value pairs for kconfigs.
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*/
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#if defined(CONFIG_ARM) || defined(CONFIG_X86) || defined(CONFIG_ARC) || defined(CONFIG_ARM64) || \
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defined(CONFIG_NIOS2) || defined(CONFIG_XTENSA) || defined(CONFIG_MIPS) || \
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defined(CONFIG_ARCH_POSIX) || defined(CONFIG_SPARC)
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#if defined(CONFIG_ARM)
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#define GEN_ABSOLUTE_SYM(name, value) \
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do { \
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__asm__(".global " #name); \
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__asm__(".set " #name ", %c0" ::"n"(value)); \
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__asm__(".type " #name ", STT_OBJECT"); \
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} while (false)
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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do { \
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__asm__(".global " #name); \
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__asm__(".set " #name ", " #value); \
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__asm__(".type " #name ", STT_OBJECT"); \
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} while (false)
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/* The following is a workaround for the RISC-V target, which
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* has a bug so it errors out on the target-agnostic '%c'.
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*
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* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112434
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*
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* > error: invalid 'asm': invalid use of '%c'
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*
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* According to commit cd83e85edc5d741f6b52c6b5995303c30bda443a,
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* '%0' is equivalent to '%c0' for the RISC-V target. We use
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* this as a workaround for now.
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*
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* This workaround should be removed when the above bug is fixed
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* in all supported Zephyr toolchain versions.
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/*
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* GNU/ARM backend does not have a proper operand modifier which does not
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* produces prefix # followed by value, such as %0 for PowerPC, Intel, and
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* MIPS. The workaround performed here is using %B0 which converts
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* the value to ~(value). Thus "n"(~(value)) is set in operand constraint
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* to output (value) in the ARM specific GEN_OFFSET macro.
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*/
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#elif defined(CONFIG_RISCV)
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#define GEN_ABSOLUTE_SYM(name, value) \
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do { \
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__asm__(".global " #name); \
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__asm__(".set " #name ", %0" ::"n"(value)); \
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__asm__(".type " #name ", STT_OBJECT"); \
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} while (false)
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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do { \
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__asm__(".global " #name); \
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__asm__(".set " #name ", " #value); \
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__asm__(".type " #name ", STT_OBJECT"); \
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} while (false)
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#define GEN_ABSOLUTE_SYM(name, value) \
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__asm__(".globl\t" #name "\n\t.equ\t" #name \
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",%B0" \
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"\n\t.type\t" #name ",%%object" : : "n"(~(value)))
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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__asm__(".globl\t" #name \
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"\n\t.equ\t" #name "," #value \
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"\n\t.type\t" #name ",%object")
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#elif defined(CONFIG_X86)
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#define GEN_ABSOLUTE_SYM(name, value) \
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__asm__(".globl\t" #name "\n\t.equ\t" #name \
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",%c0" \
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"\n\t.type\t" #name ",@object" : : "n"(value))
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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__asm__(".globl\t" #name \
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"\n\t.equ\t" #name "," #value \
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"\n\t.type\t" #name ",@object")
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#elif defined(CONFIG_ARC) || defined(CONFIG_ARM64)
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#define GEN_ABSOLUTE_SYM(name, value) \
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__asm__(".globl\t" #name "\n\t.equ\t" #name \
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",%c0" \
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"\n\t.type\t" #name ",@object" : : "n"(value))
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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__asm__(".globl\t" #name \
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"\n\t.equ\t" #name "," #value \
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"\n\t.type\t" #name ",@object")
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#elif defined(CONFIG_NIOS2) || defined(CONFIG_RISCV) || \
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defined(CONFIG_XTENSA) || defined(CONFIG_MIPS)
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/* No special prefixes necessary for constants in this arch AFAICT */
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#define GEN_ABSOLUTE_SYM(name, value) \
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__asm__(".globl\t" #name "\n\t.equ\t" #name \
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",%0" \
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"\n\t.type\t" #name ",%%object" : : "n"(value))
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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__asm__(".globl\t" #name \
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"\n\t.equ\t" #name "," #value \
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"\n\t.type\t" #name ",%object")
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#elif defined(CONFIG_ARCH_POSIX)
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#define GEN_ABSOLUTE_SYM(name, value) \
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__asm__(".globl\t" #name "\n\t.equ\t" #name \
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",%c0" \
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"\n\t.type\t" #name ",@object" : : "n"(value))
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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__asm__(".globl\t" #name \
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"\n\t.equ\t" #name "," #value \
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"\n\t.type\t" #name ",@object")
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#elif defined(CONFIG_SPARC)
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#define GEN_ABSOLUTE_SYM(name, value) \
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__asm__(".global\t" #name "\n\t.equ\t" #name \
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",%0" \
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"\n\t.type\t" #name ",#object" : : "n"(value))
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#define GEN_ABSOLUTE_SYM_KCONFIG(name, value) \
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__asm__(".globl\t" #name \
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"\n\t.equ\t" #name "," #value \
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"\n\t.type\t" #name ",#object")
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#else
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#error processor architecture not supported
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