[TargetLibraryInfo] Add support for fls, flsl, flsll

[davide]

Summary

These three function are similar to ffs but find the last bit set. They're available (at least) on FreeBSD. I'm not sure they're availalble elsewhere, I don't have a machine to test. A quick search shows Linux hasn't them.
I would like top perform fairly basic transformations on these, e.g. constant folding, so this patch can be seen as a preliminary step for those.

[echristo]

OK. Could probably use a testcase, but this is probably where you're going with the next one.

-eric

[davide]

Yes, my next patch will add a testcase. I have still some pending reviews in SimplifyLibCalls but once I get approval for them I'll a new patch to optimize fls & friends.
Thanks for reviewing!

include/llvm/Analysis/TargetLibraryInfo.def

 TLI_DEFINE_ENUM_INTERNAL(floor)
 TLI_DEFINE_STRING_INTERNAL("floor")
 /// float floorf(float x);
 TLI_DEFINE_ENUM_INTERNAL(floorf)
 TLI_DEFINE_STRING_INTERNAL("floorf")
 /// long double floorl(long double x);
 TLI_DEFINE_ENUM_INTERNAL(floorl)
 TLI_DEFINE_STRING_INTERNAL("floorl")
+/// int fls(int i);
+TLI_DEFINE_ENUM_INTERNAL(fls)
+TLI_DEFINE_STRING_INTERNAL("fls")
+/// int flsl(long int i);
+TLI_DEFINE_ENUM_INTERNAL(flsl)
+TLI_DEFINE_STRING_INTERNAL("flsl")
+/// int flsll(long long int i);
+TLI_DEFINE_ENUM_INTERNAL(flsll)
+TLI_DEFINE_STRING_INTERNAL("flsll")
 /// double fmax(double x, double y);
 TLI_DEFINE_ENUM_INTERNAL(fmax)
 TLI_DEFINE_STRING_INTERNAL("fmax")
 /// float fmaxf(float x, float y);
 TLI_DEFINE_ENUM_INTERNAL(fmaxf)
 TLI_DEFINE_STRING_INTERNAL("fmaxf")
 /// long double fmaxl(long double x, long double y);
 TLI_DEFINE_ENUM_INTERNAL(fmaxl)

lib/Analysis/TargetLibraryInfo.cpp

#endif // !NDEBUG
   switch (T.getOS()) {
   case Triple::FreeBSD:
   case Triple::Linux:
     break;
   default:
     TLI.setUnavailable(LibFunc::ffsll);
   }
 
+  // The following functions are available on at least FreeBSD:
+  // http://svn.freebsd.org/base/head/lib/libc/string/fls.c
+  // http://svn.freebsd.org/base/head/lib/libc/string/flsl.c
+  // http://svn.freebsd.org/base/head/lib/libc/string/flsll.c
+  if (!T.isOSFreeBSD()) {
+    TLI.setUnavailable(LibFunc::fls);
+    TLI.setUnavailable(LibFunc::flsl);
+    TLI.setUnavailable(LibFunc::flsll);
+  }
+
   // The following functions are available on at least Linux:
   if (!T.isOSLinux()) {
     TLI.setUnavailable(LibFunc::dunder_strdup);
     TLI.setUnavailable(LibFunc::dunder_strtok_r);
     TLI.setUnavailable(LibFunc::dunder_isoc99_scanf);
     TLI.setUnavailable(LibFunc::dunder_isoc99_sscanf);
     TLI.setUnavailable(LibFunc::under_IO_getc);
     TLI.setUnavailable(LibFunc::under_IO_putc);