[X86] Add support for __builtin_cpu_init

[craig.topper]

Summary

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.

[craig.topper]

Ping

[echristo]

One inline comment, but go ahead and commit after fixing that up.

lib/CodeGen/CGBuiltin.cpp

7292

I realize it makes sense to put this here because it doesn't require the setup, but let's go ahead and just put it in the switch statement below. I don't think avoiding the bit of setup/etc below is worth the inconsistency. :)

include/clang/Basic/BuiltinsX86.def

 #  define TARGET_HEADER_BUILTIN(ID, TYPE, ATTRS, HEADER, LANG, FEATURE) BUILTIN(ID, TYPE, ATTRS)
 #endif
 
 // FIXME: Are these nothrow/const?
 
 // 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")
 
 // Undefined Values
 //
 TARGET_BUILTIN(__builtin_ia32_undef128, "V2d", "nc", "")
 TARGET_BUILTIN(__builtin_ia32_undef256, "V4d", "nc", "")
 TARGET_BUILTIN(__builtin_ia32_undef512, "V8d", "nc", "")
 

lib/CodeGen/CGBuiltin.cpp

static Value *EmitX86SExtMask(CodeGenFunction &CGF, Value *Op,
                               llvm::Type *DstTy) {
   unsigned NumberOfElements = DstTy->getVectorNumElements();
   Value *Mask = getMaskVecValue(CGF, Op, NumberOfElements);
   return CGF.Builder.CreateSExt(Mask, DstTy, "vpmovm2");
 }
 
 Value *CodeGenFunction::EmitX86BuiltinExpr(unsigned BuiltinID,
                                            const CallExpr *E) {
+  if (BuiltinID == 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);
+  }
+
   SmallVector<Value*, 4> Ops;
 
   // Find out if any arguments are required to be integer constant expressions.
   unsigned ICEArguments = 0;
   ASTContext::GetBuiltinTypeError Error;
   getContext().GetBuiltinType(BuiltinID, Error, &ICEArguments);
   assert(Error == ASTContext::GE_None && "Should not codegen an error");
 

test/CodeGen/builtin-cpu-supports.c

 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -emit-llvm < %s| FileCheck %s
 
 // Test that we have the structure definition, the gep offsets, the name of the
 // global, the bit grab, and the icmp correct.
 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");
 
   // CHECK: [[LOAD:%[^ ]+]] = load i32, i32* getelementptr inbounds ({ i32, i32, i32, [1 x i32] }, { i32, i32, i32, [1 x i32] }* @__cpu_model, i32 0, i32 3, i32 0)
   // CHECK: [[AND:%[^ ]+]] = and i32 [[LOAD]], 256
   // CHECK: = icmp ne i32 [[AND]], 0
 
   return 0;
 }