[X86] Add a DAG combine to turn vzmovl+load into vzload if the load isn't volatile. Remove isel patterns for vzmovl+load

We currently have some isel patterns for treating vzmovl+load the same as vzload, but that shrinks the load which we shouldn't do if the load is volatile.

Rather than adding isel checks for volatile. This patch removes the patterns and teachs DAG combine to merge them into vzload when its legal to do so.

Differential Revision: https://reviews.llvm.org/D63665

llvm-svn: 364333

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 014889720a0..31c795c47d0 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33675,6 +33675,26 @@ static SDValue combineShuffle(SDNode *N, SelectionDAG &DAG,
                        Movl, N->getOperand(0).getOperand(2));
   }
 
+  // If this a vzmovl of a full vector load, replace it with a vzload, unless
+  // the load is volatile.
+  if (N->getOpcode() == X86ISD::VZEXT_MOVL && N->getOperand(0).hasOneUse() &&
+      ISD::isNormalLoad(N->getOperand(0).getNode())) {
+    LoadSDNode *LN = cast<LoadSDNode>(N->getOperand(0));
+    if (!LN->isVolatile()) {
+      SDVTList Tys = DAG.getVTList(VT, MVT::Other);
+      SDValue Ops[] = { LN->getChain(), LN->getBasePtr() };
+      SDValue VZLoad =
+          DAG.getMemIntrinsicNode(X86ISD::VZEXT_LOAD, dl, Tys, Ops,
+                                  VT.getVectorElementType(),
+                                  LN->getPointerInfo(),
+                                  LN->getAlignment(),
+                                  MachineMemOperand::MOLoad);
+      DAG.ReplaceAllUsesOfValueWith(SDValue(LN, 0), VZLoad.getValue(1));
+      return VZLoad;
+    }
+  }
+
+
   // Look for a truncating shuffle to v2i32 of a PMULUDQ where one of the
   // operands is an extend from v2i32 to v2i64. Turn it into a pmulld.
   // FIXME: This can probably go away once we default to widening legalization.