Address last round of reviews and rebase

The way we define target-independent builtins has changed which
required a rebase. Also cleaned up some comments and improved
asserts as suggested in the review.

Author: nemanjai

clang/lib/Basic/Targets/PPC.h

@@ -361,7 +361,7 @@ class LLVM_LIBRARY_VISIBILITY PPCTargetInfo : public TargetInfo {
   }
 
   // We support __builtin_cpu_supports/__builtin_cpu_is on targets that
-  // have GLIBC since it is GLIBC that provides the HWCAP[2] in the auxv.
+  // have Glibc since it is Glibc that provides the HWCAP[2] in the auxv.
   bool supportsCpuSupports() const override { return getTriple().isOSGlibc(); }
   bool supportsCpuIs() const override { return getTriple().isOSGlibc(); }
   bool validateCpuSupports(StringRef Feature) const override;

clang/lib/CodeGen/CGBuiltin.cpp

@@ -16552,6 +16552,7 @@ Value *CodeGenFunction::EmitPPCBuiltinExpr(unsigned BuiltinID,
 #define PPC_LNX_CPU(Name, NumericID) .Case(Name, NumericID)
 #include "llvm/TargetParser/PPCTargetParser.def"
                             .Default(-1U);
+    assert(NumCPUID < -1U && "Invalid CPU name. Missed by SemaChecking?");
     Value *Op0 = llvm::ConstantInt::get(Int32Ty, PPC_FAWORD_CPUID);
     llvm::Function *F = CGM.getIntrinsic(Intrinsic::ppc_fixed_addr_ld);
     Value *TheCall = Builder.CreateCall(F, {Op0}, "cpu_is");
@@ -16569,6 +16570,7 @@ Value *CodeGenFunction::EmitPPCBuiltinExpr(unsigned BuiltinID,
   .Case(Name, {FA_WORD, Bitmask})
 #include "llvm/TargetParser/PPCTargetParser.def"
             .Default({0, 0});
+    assert(BitMask && "Invalid target feature string. Missed by SemaChecking?");
     Value *Op0 = llvm::ConstantInt::get(Int32Ty, FeatureWord);
     llvm::Function *F = CGM.getIntrinsic(Intrinsic::ppc_fixed_addr_ld);
     Value *TheCall = Builder.CreateCall(F, {Op0}, "cpu_supports");

llvm/include/llvm/IR/IntrinsicsPowerPC.td

@@ -216,8 +216,8 @@ let TargetPrefix = "ppc" in {  // All intrinsics start with "llvm.ppc.".
             [llvm_float_ty, llvm_float_ty, llvm_float_ty, llvm_vararg_ty],
             [IntrNoMem]>;
   // Load of a value provided by the system library at a fixed address. Used for
-  // accessing things like HWCAP word provided by GLIBC. The immediate argument
-  // is not an address but a value defined in
+  // accessing things like the HWCAP word provided by Glibc. The immediate
+  // argument is not an address but a value defined in
   // include/llvm/TargetParser/PPCTargetParser.def. Each of the values provided
   // by Glibc is a 32-bit word.
   def int_ppc_fixed_addr_ld