[SelectionDAG] Initial support for FSHL/FSHR funnel shift opcodes (PR39467)

This is an initial patch to add a minimum level of support for funnel shifts to the SelectionDAG and to begin wiring it up to the X86 SHLD/SHRD instructions.

Some partial legalization code has been added to handle the case for 'SlowSHLD' where we want to expand instead and I've added a few DAG combines so we don't get regressions from the existing DAG builder expansion code.

Differential Revision: https://reviews.llvm.org/D54698

llvm-svn: 348353

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index dcb479e4ce1..2f4a5451a61 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1170,6 +1170,8 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
       }
     }
     break;
+    case ISD::FSHL:
+    case ISD::FSHR:
     case ISD::SRL_PARTS:
     case ISD::SRA_PARTS:
     case ISD::SHL_PARTS: {
@@ -3262,6 +3264,11 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     }
     break;
   }
+  case ISD::FSHL:
+  case ISD::FSHR:
+    if (TLI.expandFunnelShift(Node, Tmp1, DAG))
+      Results.push_back(Tmp1);
+    break;
   case ISD::SADDSAT:
   case ISD::UADDSAT:
   case ISD::SSUBSAT: