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
R=mseaborn@chromium.org

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

2 files changed, 3 insertions, 13 deletions

diff --git a/include/llvm/IR/Intrinsics.td b/include/llvm/IR/Intrinsics.td
index f9f662929b..b8f3997e9c 100644
--- a/include/llvm/IR/Intrinsics.td
+++ b/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.
diff --git a/lib/Transforms/NaCl/ExpandTls.cpp b/lib/Transforms/NaCl/ExpandTls.cpp
index 53e1c92a96..19837f7448 100644
--- a/lib/Transforms/NaCl/ExpandTls.cpp
+++ b/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();