Do some peephole optimizations to remove pointless VMOVs from Neon to integer

registers that arise from argument shuffling with the soft float ABI. These
instructions are particularly slow on Cortex A8. This fixes one half of
<rdar://problem/8674845>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128759 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 5502ca434cc93591b0c646b0dbe8f83a01554e42..d11c956b52e1f01c5a43745aa06b86261cbc22f2 100644 (file)
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -5561,6 +5561,37 @@ static SDValue PerformVMOVRRDCombine(SDNode *N,
   SDValue InDouble = N->getOperand(0);
   if (InDouble.getOpcode() == ARMISD::VMOVDRR)
     return DCI.CombineTo(N, InDouble.getOperand(0), InDouble.getOperand(1));
+
+  // vmovrrd(load f64) -> (load i32), (load i32)
+  SDNode *InNode = InDouble.getNode();
+  if (ISD::isNormalLoad(InNode) && InNode->hasOneUse() &&
+      InNode->getValueType(0) == MVT::f64 &&
+      InNode->getOperand(1).getOpcode() == ISD::FrameIndex &&
+      !cast<LoadSDNode>(InNode)->isVolatile()) {
+    // TODO: Should this be done for non-FrameIndex operands?
+    LoadSDNode *LD = cast<LoadSDNode>(InNode);
+
+    SelectionDAG &DAG = DCI.DAG;
+    DebugLoc DL = LD->getDebugLoc();
+    SDValue BasePtr = LD->getBasePtr();
+    SDValue NewLD1 = DAG.getLoad(MVT::i32, DL, LD->getChain(), BasePtr,
+                                 LD->getPointerInfo(), LD->isVolatile(),
+                                 LD->isNonTemporal(), LD->getAlignment());
+
+    SDValue OffsetPtr = DAG.getNode(ISD::ADD, DL, MVT::i32, BasePtr,
+                                    DAG.getConstant(4, MVT::i32));
+    SDValue NewLD2 = DAG.getLoad(MVT::i32, DL, NewLD1.getValue(1), OffsetPtr,
+                                 LD->getPointerInfo(), LD->isVolatile(),
+                                 LD->isNonTemporal(),
+                                 std::min(4U, LD->getAlignment() / 2));
+
+    DAG.ReplaceAllUsesOfValueWith(SDValue(LD, 1), NewLD2.getValue(1));
+    SDValue Result = DCI.CombineTo(N, NewLD1, NewLD2);
+    DCI.RemoveFromWorklist(LD);
+    DAG.DeleteNode(LD);
+    return Result;
+  }
+
   return SDValue();
 }
 

diff --git a/test/CodeGen/ARM/fp-arg-shuffle.ll b/test/CodeGen/ARM/fp-arg-shuffle.ll
new file mode 100644 (file)
index 0000000..59303ac
--- /dev/null
+++ b/test/CodeGen/ARM/fp-arg-shuffle.ll
@@ -0,0 +1,11 @@
+; RUN: llc < %s -march=arm -mattr=+neon -float-abi=soft | FileCheck %s
+
+; CHECK: function1
+; CHECK-NOT: vmov r
+define double @function1(double %a, double %b, double %c, double %d, double %e, double %f) nounwind noinline ssp {
+entry:
+  %call = tail call double @function2(double %f, double %e, double %d, double %c, double %b, double %a) nounwind
+  ret double %call
+}
+
+declare double @function2(double, double, double, double, double, double)