search for: neon_help

...for each variable where the behavior is not undefined? Such a value must exist, or the entire function is useless if it always has undefined behavior. Sure, testing on 1 such value (or a random) value won't prove that the result is correct, but may help finding trivial miscompilations like the neon_helper case. Alternatively a testcase could be manually constructed for the top 10 functions in the size comparison charts, and see whether they are miscompiled. Repeat until top 10 has no miscompilations. > > A potential solution is "under-constrained execution": > > http://ww...

Hi Torok- > Could you also add a main() for each of these files, and do > a very simple test that the optimized functions actually work? Unfortunately, testing isolated C functions is much harder than just passing them random data! Consider this function: int foo (int x, int y) { return x+y; } The behavior of foo() is undefined when x+y overflows. If course it is trivial to come

...ot undefined? > Such a value must exist, or the entire function is useless if it always > has undefined behavior. Good point :). > Sure, testing on 1 such value (or a random) value won't prove that the > result is correct, but may help finding trivial > miscompilations like the neon_helper case. Are you absolutely sure it's a miscompilation? I have already shot myself in the foot a couple times on the GCC mailing list or bugzilla by pointing out a bug that turned out to be code with subtle undefined behavior... > Alternatively a testcase could be manually constructed fo...

...n64 compiler > Hi, Could you also add a main() for each of these files, and do a very simple test that the optimized functions actually work? At least for functions that take only integers and return integers this could be automated if you compare -O0 output with the optimized outputs. The neon_helper.c testcase is clearly misoptimized by gcc-head here: http://embed.cs.utah.edu/embarrassing/jan_10/harvest/compare_clang-head_gcc-head/compare_23BD1620_disasm.shtml Try calling it like this: int main() { printf("%d\n", helper_neon_rshl_s8(0x12345, 15)); return 0; } Prints 74496...

...ue must exist, or the entire function is useless if it always >> has undefined behavior. > > Good point :). > >> Sure, testing on 1 such value (or a random) value won't prove that the >> result is correct, but may help finding trivial >> miscompilations like the neon_helper case. > > Are you absolutely sure it's a miscompilation? I have already shot > myself in the foot a couple times on the GCC mailing list or bugzilla > by pointing out a bug that turned out to be code with subtle undefined > behavior... Well if it is not then it is a qemu bug,...

Hi folks, I've posted an updated code size comparison between LLVM, GCC, and others here: http://embed.cs.utah.edu/embarrassing/ New in this version: - much larger collection of harvested functions: more than 360,000 - bug fixes and UI improvements - added the x86 Open64 compiler John