[X86] Pre-define __MOVBE__ when the target supports it.

[craig.topper]

What utility does MOVBE serve? We don't have an instrinsic headers that needs this like the others. As far as I can tell gcc doesn't define this.

[erikjv]

GCC doesn't define this, but icc does. Just like e.g. AVX512CD, it can be used to conditionally enable code that uses the instruction as a fast implementation for an algorithm.

[craig.topper]

Does icc have an intrinsic for it?

lib/Basic/Targets.cpp

       HasAVX512VL;
   bool HasSHA;
   bool HasCX16;
+  bool HasMOVBE;
 
   /// \brief Enumeration of all of the X86 CPUs supported by Clang.
   ///

         HasADX(false), HasTBM(false), HasFMA(false), HasF16C(false),
         HasAVX512CD(false), HasAVX512ER(false), HasAVX512PF(false),
         HasAVX512DQ(false), HasAVX512BW(false), HasAVX512VL(false),
-        HasSHA(false), HasCX16(false), CPU(CK_Generic), FPMath(FP_Default) {
+        HasSHA(false), HasCX16(false), HasMOVBE(false), CPU(CK_Generic),
+        FPMath(FP_Default) {
     BigEndian = false;
     LongDoubleFormat = &llvm::APFloat::x87DoubleExtended;
   }

     setFeatureEnabledImpl(Features, "bmi2", true);
     setFeatureEnabledImpl(Features, "rtm", true);
     setFeatureEnabledImpl(Features, "fma", true);
+    setFeatureEnabledImpl(Features, "movbe", true);
     // FALLTHROUGH
   case CK_IvyBridge:
     setFeatureEnabledImpl(Features, "rdrnd", true);

     setFeatureEnabledImpl(Features, "aes", true);
     setFeatureEnabledImpl(Features, "pclmul", true);
     setFeatureEnabledImpl(Features, "cx16", true);
+    setFeatureEnabledImpl(Features, "movbe", true);
     break;
   case CK_K6_2:
   case CK_K6_3:

       continue;
     }
 
+    if (Feature == "movbe") {
+      HasMOVBE = true;
+      continue;
+    }
+
     assert(Features[i][0] == '+' && "Invalid target feature!");
     X86SSEEnum Level = llvm::StringSwitch<X86SSEEnum>(Feature)
       .Case("avx512f", AVX512F)

   if (HasF16C)
     Builder.defineMacro("__F16C__");
 
+  if (HasMOVBE)
+    Builder.defineMacro("__MOVBE__");
+
   if (HasAVX512CD)
     Builder.defineMacro("__AVX512CD__");
   if (HasAVX512ER)

       .Case("bmi", HasBMI)
       .Case("bmi2", HasBMI2)
       .Case("cx16", HasCX16)
+      .Case("movbe", HasMOVBE)
       .Case("f16c", HasF16C)
       .Case("fma", HasFMA)
       .Case("fma4", XOPLevel >= FMA4)