[Intrinsic] Signed Fixed Point Multiplication Intrinsic

Add an intrinsic that takes 2 signed integers with the scale of them provided
as the third argument and performs fixed point multiplication on them.

This is a part of implementing fixed point arithmetic in clang where some of
the more complex operations will be implemented as intrinsics.

Differential Revision: https://reviews.llvm.org/D54719

llvm-svn: 348912

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 2f4a5451a61..f1c6d63982e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1128,6 +1128,12 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
     Action = TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0));
     break;
   }
+  case ISD::SMULFIX: {
+    unsigned Scale = Node->getConstantOperandVal(2);
+    Action = TLI.getFixedPointOperationAction(Node->getOpcode(),
+                                              Node->getValueType(0), Scale);
+    break;
+  }
   case ISD::MSCATTER:
     Action = TLI.getOperationAction(Node->getOpcode(),
                     cast<MaskedScatterSDNode>(Node)->getValue().getValueType());
@@ -3276,6 +3282,10 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Results.push_back(TLI.getExpandedSaturationAdditionSubtraction(Node, DAG));
     break;
   }
+  case ISD::SMULFIX: {
+    Results.push_back(TLI.getExpandedFixedPointMultiplication(Node, DAG));
+    break;
+  }
   case ISD::SADDO:
   case ISD::SSUBO: {
     SDValue LHS = Node->getOperand(0);