Cleanup useless/non-constexpr branchs #2449

Job	Run time
externals (clang, x86, -msse2)	44m 45s
macosx (clang, x86_osx, -mavx)	1h 41m 12s
externals (gcc, x86, -msse2)	54m 6s
no_pch (clang, x86, -msse2)	57m 41s
no_pch (gcc, x86, -msse2)	1h 2m 17s
nosimd (clang, x86, -DEVE_NO_SIMD)	38m 40s
riscv (clang, riscv, -mrvv-vector-bits=128)	33m 5s
nosimd (gcc, x86, -DEVE_NO_SIMD)	49m 27s
x86-clang (clang, x86, -msse4.2)	17m 56s
x86-clang (clang, x86, -mavx)	23m 57s
x86-clang (clang, x86, -mavx2)	22m 29s
arm (clang, aarch64, -Wno-psabi)	32m 29s
arm (clang, arm, -Wno-psabi)	33m 22s
other-arch (gcc, sve256, -Wno-psabi)	1h 5m 54s
other-arch (gcc, sve512, -Wno-psabi)	2h 25m 57s
other-arch (gcc, ppc64, -Wno-psabi)	40m 7s
avx512 (clang, x86, -march=skylake-avx512)	36m 48s
avx512 (gcc, x86, -march=skylake-avx512)	1h 2m 31s
other-cases (clang_libcpp, x86, -msse2)	24m 33s
other-cases (clang, x86, -mavx2 -mbmi2 -DEVE_USE_BMI_ON_AVX2)	28m 57s
other-cases (gcc, x86, -mavx2 -mbmi2 -DEVE_USE_BMI_ON_AVX2)	55m 45s
x86-gcc (gcc, x86, -msse4.2)	16m 7s
x86-gcc (gcc, x86, -mavx)	16m 27s
x86-gcc (gcc, x86, -mavx2)	21m 15s
	18h 5m 47s

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