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Diffstat (limited to 'include/tools/simdsupport.hxx')
| -rw-r--r-- | include/tools/simdsupport.hxx | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/tools/simdsupport.hxx b/include/tools/simdsupport.hxx index bc9227223da0..738b34e072db 100644 --- a/include/tools/simdsupport.hxx +++ b/include/tools/simdsupport.hxx @@ -8,6 +8,16 @@ * */ +// IMPORTANT: Having CPU-specific routines turned out to be a maintenance +// problem, because of various problems such as compilers moving CPU-specific +// code out of #ifdef code into static initialization or our code using C++ +// features that caused the compiler to emit code that used CPU-specific +// instructions (even cpuid.hxx isn't safe, see the comment there). +// The only safe usage is using CPU-specific code that's always available, +// such as SSE2-specific code for x86_64. Do not use for anything else +// unless you really know what you are doing (and you check git history +// to learn from past problems). + // Determine the compiler support for SIMD compiler intrinsics. // This changes from one compiled unit to the other, depending if // the support has been detected and if the compiled unit contains |