[ARM] Add support for mrrc/mrrc2 intrinsics.

Reapplying patch as it was reverted when it was first
committed because of an assertion failure when the
mrrc2 intrinsic was called in ARM mode. The failure
was happening because the instruction was being built
in ARMISelDAGToDAG.cpp and the tablegen description for
mrrc2 instruction doesn't allow you to use a predicate.

The ARM architecture manuals do say that mrrc2 in ARM
mode can be predicated with AL in assembly but this has
no effect on the encoding of the instruction as the top
4 bits will always be 1111 not 1110 which is the encoding
for the condition AL.

Differential Revision: http://reviews.llvm.org/D21408

llvm-svn: 272982

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 4af21748374..efe62945771 100644
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -3335,6 +3335,41 @@ void ARMDAGToDAGISel::Select(SDNode *N) {
     default:
       break;
 
+    case Intrinsic::arm_mrrc:
+    case Intrinsic::arm_mrrc2: {
+      SDLoc dl(N);
+      SDValue Chain = N->getOperand(0);
+      unsigned Opc;
+
+      if (Subtarget->isThumb())
+        Opc = (IntNo == Intrinsic::arm_mrrc ? ARM::t2MRRC : ARM::t2MRRC2);
+      else
+        Opc = (IntNo == Intrinsic::arm_mrrc ? ARM::MRRC : ARM::MRRC2);
+
+      SmallVector<SDValue, 5> Ops;
+      Ops.push_back(getI32Imm(cast<ConstantSDNode>(N->getOperand(2))->getZExtValue(), dl)); /* coproc */
+      Ops.push_back(getI32Imm(cast<ConstantSDNode>(N->getOperand(3))->getZExtValue(), dl)); /* opc */
+      Ops.push_back(getI32Imm(cast<ConstantSDNode>(N->getOperand(4))->getZExtValue(), dl)); /* CRm */
+
+      // The mrrc2 instruction in ARM doesn't allow predicates, the top 4 bits of the encoded
+      // instruction will always be '1111' but it is possible in assembly language to specify
+      // AL as a predicate to mrrc2 but it doesn't make any difference to the encoded instruction.
+      if (Opc != ARM::MRRC2) {
+        Ops.push_back(getAL(CurDAG, dl));
+        Ops.push_back(CurDAG->getRegister(0, MVT::i32));
+      }
+
+      Ops.push_back(Chain);
+
+      // Writes to two registers.
+      std::vector<EVT> RetType;
+      RetType.push_back(MVT::i32);
+      RetType.push_back(MVT::i32);
+      RetType.push_back(MVT::Other);
+
+      ReplaceNode(N, CurDAG->getMachineNode(Opc, dl, RetType, Ops));
+      return;
+    }
     case Intrinsic::arm_ldaexd:
     case Intrinsic::arm_ldrexd: {
       SDLoc dl(N);