Mark getc_unlocked as unavailable by default

[rprichard]

Summary

Before D45736, getc_unlocked was available by default, but turned off
for non-Cygwin/non-MinGW Windows. D45736 then added 9 more unlocked
functions, which were unavailable by default, but it also:

• left getc_unlocked enabled by default,
• removed the disabling line for Windows, and
• added code to enable getc_unlocked for GNU, Android, and OSX.

For consistency, make getc_unlocked unavailable by default. Maybe this
was the intent of D45736 anyway.

[rprichard]

Update test.

[rprichard]

I noticed this inconsistency while reviewing D107509.

For the MSVC environment, Clang currently annotates getc_unlocked with nocapture, which could technically be wrong if getc_unlocked were an unrelated function. MSVC's CRT doesn't define *_unlocked functions. https://godbolt.org/z/GreGM6x8G.

(MSVC does define *_nolock functions, which look similar, but I haven't looked closely.)

[efriedma]

LGTM

[MaskRay]

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

514 ↗

(On Diff #364335)

What does this check?

Many times it'd be better to replace negative checks with positive checks, with a comment stating that we don't want to see certain things.

Negative checks can quite easily become stale. For example, if another function is inserted below and it has a #, the test will fail weirdly.

[rprichard]

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

514 ↗

(On Diff #364335)

I copied it from the similar test cases. I think it's trying to check that the function declaration doesn't have an #nnn attribute on the end. Maybe {{$}} would be a better way of doing that.

I think I'll upload that in a separate patch.

llvm/lib/Analysis/TargetLibraryInfo.cpp

static void initialize(TargetLibraryInfoImpl &TLI, const Triple &T,
   // Verify that the StandardNames array is in alphabetical order.
   assert(
       llvm::is_sorted(StandardNames,
                       [](StringRef LHS, StringRef RHS) { return LHS < RHS; }) &&
       "TargetLibraryInfoImpl function names must be sorted");
 
   // Set IO unlocked variants as unavailable
   // Set them as available per system below
+  TLI.setUnavailable(LibFunc_getc_unlocked);
   TLI.setUnavailable(LibFunc_getchar_unlocked);
   TLI.setUnavailable(LibFunc_putc_unlocked);
   TLI.setUnavailable(LibFunc_putchar_unlocked);
   TLI.setUnavailable(LibFunc_fputc_unlocked);
   TLI.setUnavailable(LibFunc_fgetc_unlocked);
   TLI.setUnavailable(LibFunc_fread_unlocked);
   TLI.setUnavailable(LibFunc_fwrite_unlocked);
   TLI.setUnavailable(LibFunc_fputs_unlocked);