The customary LLVM way of obtaining intrinsics is with

    Intrinsic::getDeclaration and use the definition in
    include/llvm/Intrinsics.td

    This also makes the attribute on the intrinsic to be more
    consistent with the back-end (code-gen), which automatically assumes
    it's ReadNone (because this is what Intrinsics.td) defines.

    Using ReadNone rather than ReadOnly may be not strictly correct because
    the intrinsic depends on the value of the TP. However, this attribute is
    not really used anywhere in IR optimizations, and in the backend the
    intrinsic is ReadNone anyhow (the IR setting gets overridden).

    If we run into any problems with this in the future, we may consider
    handling the lowering of this intrinsic in
    TargetLowering::LowerINTRINSIC_W_CHAIN rather than in
    TargetLowering::LowerINTRINSIC_WO_CHAIN.

BUG=None
[email protected]

Review URL: https://codereview.chromium.org/14643019

Author: eliben

include/llvm/IR/Intrinsics.td

@@ -479,8 +479,7 @@ def int_nacl_longjmp  : Intrinsic<[], [llvm_ptr_ty, llvm_i32_ty],
                                   [IntrNoReturn]>;
 
 // Fast built-in version of NaCl's tls_get() IRT interface.
-def int_nacl_read_tp : Intrinsic<[llvm_ptr_ty], [], [IntrNoMem]>,
-                       GCCBuiltin<"__builtin_nacl_read_tp">;
+def int_nacl_read_tp : Intrinsic<[llvm_ptr_ty], [], [IntrNoMem]>;
 
 // The following intrinsics provide target-specific implementations of
 // the interface in native_client/src/untrusted/nacl/tls_params.h.

lib/Transforms/NaCl/ExpandTls.cpp

@@ -29,6 +29,7 @@
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/NaCl.h"
@@ -233,17 +234,7 @@ static PointerType *buildTlsTemplate(Module &M, std::vector<VarInfo> *TlsVars) {
 static void rewriteTlsVars(Module &M, std::vector<VarInfo> *TlsVars,
                            PointerType *TemplatePtrType) {
   // Set up the intrinsic that reads the thread pointer.
-  Type *i8 = Type::getInt8Ty(M.getContext());
-  FunctionType *ReadTpType = FunctionType::get(PointerType::get(i8, 0),
-                                               /*isVarArg=*/false);
-  AttrBuilder B;
-  B.addAttribute(Attribute::ReadOnly);
-  B.addAttribute(Attribute::NoUnwind);
-  AttributeSet ReadTpAttrs = AttributeSet::get(
-      M.getContext(), AttributeSet::FunctionIndex, B);
-  Constant *ReadTpFunc = M.getOrInsertTargetIntrinsic("llvm.nacl.read.tp",
-                                                      ReadTpType,
-                                                      ReadTpAttrs);
+  Function *ReadTpFunc = Intrinsic::getDeclaration(&M, Intrinsic::nacl_read_tp);
 
   for (std::vector<VarInfo>::iterator VarInfo = TlsVars->begin();
        VarInfo != TlsVars->end();