Peter Maydell <peter.mayd...@linaro.org> writes: > On 11 November 2015 at 07:51, Junaid Shuja <junaidsh...@siswa.um.edu.my> > wrote: >> Hi, >> I am working on ARM/NEON instructions. I want to know which neon helper >> function corresponds to the neon instructions. As a test case, I have a >> source file with loads of vadd.i32 instructions. I want to trace which neon >> helper functions is called. I used a very crude approach: printf in >> neon_add_u16 funtion and compiled source again. But no printf showed on >> program execution. I need help regarding tracing of neon helpers. > > Integer addition is a simple operation so we can do it directly > in the generated code; we don't need a helper for it, even as a > Neon instruction. Generally we only have helper functions for > operations that are too complicated to do directly inline. > So there isn't a simple "one neon instruction, one helper function" > mapping. Where we do have a helper function, the helper > may work on one "lane" of Neon data (meaning it gets called > more than once for each instruction) or it may work on several > lanes at once. > > To find out how we handle a particular Neon instruction, you need > to look at disas_neon_data_insn and see what it does with the > insn (it may be easiest to do this by putting a breakpoint on > it and stepping through with a debugger). Where this code calls > gen_helper_* functions, it is emitting generated code which will > later call the relevant helper at runtime.
Random musing: I wonder how easy it would be to emit the helper function name in the out_asm dump? > > thanks > -- PMM -- Alex Bennée
