[CodeGen][X86] Fuchsia supports sincos* libcalls and sin+cos->sincos optimization

[mcgrathr]

Please land it for me when approved.

[phosek]

LGTM

lib/CodeGen/TargetLoweringBase.cpp

if (TT.isOSDarwin()) {
     // FIXME: What about other targets?
     Names[RTLIB::FPEXT_F16_F32] = "__extendhfsf2";
     Names[RTLIB::FPROUND_F32_F16] = "__truncsfhf2";
   } else {
     Names[RTLIB::FPEXT_F16_F32] = "__gnu_h2f_ieee";
     Names[RTLIB::FPROUND_F32_F16] = "__gnu_f2h_ieee";
   }
 
-  if (TT.isGNUEnvironment()) {
+  if (TT.isGNUEnvironment() || TT.isOSFuchsia()) {
     Names[RTLIB::SINCOS_F32] = "sincosf";
     Names[RTLIB::SINCOS_F64] = "sincos";
     Names[RTLIB::SINCOS_F80] = "sincosl";
     Names[RTLIB::SINCOS_F128] = "sincosl";
     Names[RTLIB::SINCOS_PPCF128] = "sincosl";
   }
 
   if (TT.isOSOpenBSD()) {

lib/Target/X86/X86Subtarget.cpp

const char *X86Subtarget::getBZeroEntry() const {
   if (getTargetTriple().isMacOSX() &&
       !getTargetTriple().isMacOSXVersionLT(10, 6))
     return "__bzero";
 
   return nullptr;
 }
 
 bool X86Subtarget::hasSinCos() const {
-  return getTargetTriple().isMacOSX() &&
-    !getTargetTriple().isMacOSXVersionLT(10, 9) &&
-    is64Bit();
+  if (getTargetTriple().isMacOSX()) {
+    return !getTargetTriple().isMacOSXVersionLT(10, 9) && is64Bit();
+  } else if (getTargetTriple().isOSFuchsia()) {
+    return true;
+  }
+  return false;
 }
 
 /// Return true if the subtarget allows calls to immediate address.
 bool X86Subtarget::isLegalToCallImmediateAddr() const {
   // FIXME: I386 PE/COFF supports PC relative calls using IMAGE_REL_I386_REL32
   // but WinCOFFObjectWriter::RecordRelocation cannot emit them.  Once it does,
   // the following check for Win32 should be removed.
   if (In64BitMode || isTargetWin32())

test/CodeGen/X86/sincos-opt.ll

 ; RUN: llc < %s -mtriple=x86_64-apple-macosx10.9.0 -mcpu=core2 | FileCheck %s --check-prefix=OSX_SINCOS
 ; RUN: llc < %s -mtriple=x86_64-apple-macosx10.8.0 -mcpu=core2 | FileCheck %s --check-prefix=OSX_NOOPT
 ; RUN: llc < %s -mtriple=x86_64-pc-linux-gnu -mcpu=core2 | FileCheck %s --check-prefix=GNU_SINCOS
 ; RUN: llc < %s -mtriple=x86_64-pc-linux-gnu -mcpu=core2 -enable-unsafe-fp-math | FileCheck %s --check-prefix=GNU_SINCOS_FASTMATH
 ; RUN: llc < %s -mtriple=x86_64-pc-linux-gnux32 -mcpu=core2 -enable-unsafe-fp-math | FileCheck %s --check-prefix=GNU_SINCOS_FASTMATH
+; RUN: llc < %s -mtriple=x86_64-fuchsia -mcpu=core2 | FileCheck %s --check-prefix=GNU_SINCOS
+; RUN: llc < %s -mtriple=x86_64-fuchsia -mcpu=core2 -enable-unsafe-fp-math | FileCheck %s --check-prefix=GNU_SINCOS_FASTMATH
 
 ; Combine sin / cos into a single call unless they may write errno (as
 ; captured by readnone attrbiute, controlled by clang -fmath-errno
 ; setting).
 ; rdar://13087969
 ; rdar://13599493
 
 define float @test1(float %x) nounwind {