Commits on Mar 2, 2023

1. Use environment for mips feature detection …

   The -march= option is perfectly happy to emit code to run on a processor
   different than the one on which it is being compiled.  This results in
   misdetection of mips features because the test compiles specify that a
   given extension should be emitted, but this does not check whether or
   not this corresponds to the subarchitecture targeted in CFLAGS by the
   rest of the build.
   
   $ echo "void main(void){ __asm__ volatile(\"punpcklhw \$f0, \$f0, \$f0\"); }" > test.c
   $ CFLAGS="-march=loongson3a" make test
   cc -march=loongson3a    test.c   -o test
   $ ./test
   Illegal instruction
   $ CFLAGS="-march=native" make -B test
   cc -march=native    test.c   -o test
   /tmp/ccLbeyM1.s: Assembler messages:
   /tmp/ccLbeyM1.s:25: Error: opcode not supported on this processor: octeon2 (mips64r2) `punpcklhw $f0,$f0,$f0'
   make: *** [<builtin>: test] Error 1
   
   This leads to -march=loongson3a getting appended to CFLAGS, which may
   conflict with previously specified -march= levels for the build, or
   other options.  Calling make in the test will use whatever CC/CFLAGS are
   specified in the environment to determine whether the actual compile
   command line to be used in the build supports these features.
   
   Fixes: 8b942ee ("Adjust the mmi/msa detection mode for mips platform.")

   

   matoro committed Mar 2, 2023
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