[PowerPC] Add support for llvm.thread.pointer intrinsic

[kbarton]

LGTM.
Could you please add a short comment what this is being used for?

[• koriakin]

In D19304#411048, @kbarton wrote:

LGTM.
Could you please add a short comment what this is being used for?

Alright, I'll add:

// Reads the thread pointer register, used for __builtin_thread_pointer.

Before the IntrinsicID check.

I don't have any particular use case for this builtin in mind on PowerPC - I added the SystemZ version for use in sanitizers, and it's already supported by ARM/AArch64, so I'm submitting versions for other arches for parity.

llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp

static bool getVectorCompareInfo(SDValue Intrin, int &CompareOpc,
   }
   return true;
 }
 
 /// LowerINTRINSIC_WO_CHAIN - If this is an intrinsic that we want to custom
 /// lower, do it, otherwise return null.
 SDValue PPCTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
                                                    SelectionDAG &DAG) const {
+  unsigned IntrinsicID =
+    cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
+
+  if (IntrinsicID == Intrinsic::thread_pointer) {
+    // Reads the thread pointer register, used for __builtin_thread_pointer.
+    bool is64bit = Subtarget.isPPC64();
+    return DAG.getRegister(is64bit ? PPC::X13 : PPC::R2,
+                           is64bit ? MVT::i64 : MVT::i32);
+  }
+
   // If this is a lowered altivec predicate compare, CompareOpc is set to the
   // opcode number of the comparison.
   SDLoc dl(Op);
   int CompareOpc;
   bool isDot;
   if (!getVectorCompareInfo(Op, CompareOpc, isDot, Subtarget))
     return SDValue();    // Don't custom lower most intrinsics.
 

llvm/trunk/test/CodeGen/PowerPC/thread-pointer.ll

+; RUN: llc < %s -mtriple=powerpc-unknown-linux-gnu | FileCheck %s --check-prefix=CHECK-32
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu | FileCheck %s --check-prefix=CHECK-64
+; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu | FileCheck %s --check-prefix=CHECK-64
+
+; Function Attrs: nounwind readnone
+declare i8* @llvm.thread.pointer() #1
+
+define i8* @thread_pointer() {
+; CHECK-32-LABEL: @thread_pointer
+; CHECK-32: mr 3, 2
+; CHECK-32: blr
+; CHECK-64-LABEL: @thread_pointer
+; CHECK-64: mr 3, 13
+; CHECK-64: blr
+  %1 = tail call i8* @llvm.thread.pointer()
+  ret i8* %1
+}