[X86] Add support for __builtin_cpu_init

This adds builtin_cpu_init which will emit a call to cpu_indicator_init in libgcc or compiler-rt.

This is needed to support builtin_cpu_supports/builtin_cpu_is in an ifunc resolver.

Differential Revision: https://reviews.llvm.org/D36336

llvm-svn: 311874

clang/include/clang/Basic/BuiltinsX86.def

@@ -32,6 +32,7 @@
 // Miscellaneous builtin for checking x86 cpu features.
 // TODO: Make this somewhat generic so that other backends
 // can use it?
+BUILTIN(__builtin_cpu_init, "v", "n")
 BUILTIN(__builtin_cpu_supports, "bcC*", "nc")
 BUILTIN(__builtin_cpu_is, "bcC*", "nc")
 

clang/lib/CodeGen/CGBuiltin.cpp

@@ -7404,9 +7404,6 @@ static Value *EmitX86CpuIs(CodeGenFunction &CGF, const CallExpr *E) {
 
 Value *CodeGenFunction::EmitX86BuiltinExpr(unsigned BuiltinID,
                                            const CallExpr *E) {
-  if (BuiltinID == X86::BI__builtin_cpu_is)
-    return EmitX86CpuIs(*this, E);
-
   SmallVector<Value*, 4> Ops;
 
   // Find out if any arguments are required to be integer constant expressions.
@@ -7457,6 +7454,15 @@ Value *CodeGenFunction::EmitX86BuiltinExpr(unsigned BuiltinID,
 
   switch (BuiltinID) {
   default: return nullptr;
+  case X86::BI__builtin_cpu_init: {
+    llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy,
+                                                      /*Variadic*/false);
+    llvm::Constant *Func = CGM.CreateRuntimeFunction(FTy,
+                                                     "__cpu_indicator_init");
+    return Builder.CreateCall(Func);
+  }
+  case X86::BI__builtin_cpu_is:
+    return EmitX86CpuIs(*this, E);
   case X86::BI__builtin_cpu_supports: {
     const Expr *FeatureExpr = E->getArg(0)->IgnoreParenCasts();
     StringRef FeatureStr = cast<StringLiteral>(FeatureExpr)->getString();

clang/test/CodeGen/builtin-cpu-supports.c

@@ -5,6 +5,10 @@
 extern void a(const char *);
 
 int main() {
+  __builtin_cpu_init();
+
+  // CHECK: call void @__cpu_indicator_init
+
   if (__builtin_cpu_supports("sse4.2"))
     a("sse4.2");