Optimizing (zext A + zext B) * C, to (VMULL A, C) + (VMULL B, C) during

isel lowering to fold the zero-extend's and take advantage of no-stall
back to back vmul + vmla:
 vmull q0, d4, d6
 vmlal q0, d5, d6
is faster than
 vaddl q0, d4, d5
 vmovl q1, d6                                                                                                                                                                             
 vmul  q0, q0, q1

This allows us to vmull + vmlal for:
    f = vmull_u8(   vget_high_u8(s), c);
    f = vmlal_u8(f, vget_low_u8(s),  c);

rdar://9197392

llvm-svn: 128444

1 files changed, 81 insertions, 15 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 623393df4aa..3267ea88f39 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -4370,6 +4370,28 @@ static SDValue SkipExtension(SDNode *N, SelectionDAG &DAG) {
                      MVT::getVectorVT(TruncVT, NumElts), Ops.data(), NumElts);
 }
 
+static bool isAddSubSExt(SDNode *N, SelectionDAG &DAG) {
+  unsigned Opcode = N->getOpcode();
+  if (Opcode == ISD::ADD || Opcode == ISD::SUB) {
+    SDNode *N0 = N->getOperand(0).getNode();
+    SDNode *N1 = N->getOperand(1).getNode();
+    return N0->hasOneUse() && N1->hasOneUse() &&
+      isSignExtended(N0, DAG) && isSignExtended(N1, DAG);
+  }
+  return false;
+}
+
+static bool isAddSubZExt(SDNode *N, SelectionDAG &DAG) {
+  unsigned Opcode = N->getOpcode();
+  if (Opcode == ISD::ADD || Opcode == ISD::SUB) {
+    SDNode *N0 = N->getOperand(0).getNode();
+    SDNode *N1 = N->getOperand(1).getNode();
+    return N0->hasOneUse() && N1->hasOneUse() &&
+      isZeroExtended(N0, DAG) && isZeroExtended(N1, DAG);
+  }
+  return false;
+}
+
 static SDValue LowerMUL(SDValue Op, SelectionDAG &DAG) {
   // Multiplications are only custom-lowered for 128-bit vectors so that
   // VMULL can be detected.  Otherwise v2i64 multiplications are not legal.
@@ -4378,26 +4400,70 @@ static SDValue LowerMUL(SDValue Op, SelectionDAG &DAG) {
   SDNode *N0 = Op.getOperand(0).getNode();
   SDNode *N1 = Op.getOperand(1).getNode();
   unsigned NewOpc = 0;
-  if (isSignExtended(N0, DAG) && isSignExtended(N1, DAG))
+  bool isMLA = false;
+  bool isN0SExt = isSignExtended(N0, DAG);
+  bool isN1SExt = isSignExtended(N1, DAG);
+  if (isN0SExt && isN1SExt)
     NewOpc = ARMISD::VMULLs;
-  else if (isZeroExtended(N0, DAG) && isZeroExtended(N1, DAG))
-    NewOpc = ARMISD::VMULLu;
-  else if (VT == MVT::v2i64)
-    // Fall through to expand this.  It is not legal.
-    return SDValue();
-  else
-    // Other vector multiplications are legal.
-    return Op;
+  else {
+    bool isN0ZExt = isZeroExtended(N0, DAG);
+    bool isN1ZExt = isZeroExtended(N1, DAG);
+    if (isN0ZExt && isN1ZExt)
+      NewOpc = ARMISD::VMULLu;
+    else if (isN1SExt || isN1ZExt) {
+      // Look for (s/zext A + s/zext B) * (s/zext C). We want to turn these
+      // into (s/zext A * s/zext C) + (s/zext B * s/zext C)
+      if (isN1SExt && isAddSubSExt(N0, DAG)) {
+        NewOpc = ARMISD::VMULLs;
+        isMLA = true;
+      } else if (isN1ZExt && isAddSubZExt(N0, DAG)) {
+        NewOpc = ARMISD::VMULLu;
+        isMLA = true;
+      } else if (isN0ZExt && isAddSubZExt(N1, DAG)) {
+        std::swap(N0, N1);
+        NewOpc = ARMISD::VMULLu;
+        isMLA = true;
+      }
+    }
+
+    if (!NewOpc) {
+      if (VT == MVT::v2i64)
+        // Fall through to expand this.  It is not legal.
+        return SDValue();
+      else
+        // Other vector multiplications are legal.
+        return Op;
+    }
+  }
 
   // Legalize to a VMULL instruction.
   DebugLoc DL = Op.getDebugLoc();
-  SDValue Op0 = SkipExtension(N0, DAG);
+  SDValue Op0;
   SDValue Op1 = SkipExtension(N1, DAG);
-
-  assert(Op0.getValueType().is64BitVector() &&
-         Op1.getValueType().is64BitVector() &&
-         "unexpected types for extended operands to VMULL");
-  return DAG.getNode(NewOpc, DL, VT, Op0, Op1);
+  if (!isMLA) {
+    Op0 = SkipExtension(N0, DAG);
+    assert(Op0.getValueType().is64BitVector() &&
+           Op1.getValueType().is64BitVector() &&
+           "unexpected types for extended operands to VMULL");
+    return DAG.getNode(NewOpc, DL, VT, Op0, Op1);
+  }
+
+  // Optimizing (zext A + zext B) * C, to (VMULL A, C) + (VMULL B, C) during
+  // isel lowering to take advantage of no-stall back to back vmul + vmla.
+  //   vmull q0, d4, d6
+  //   vmlal q0, d5, d6
+  // is faster than
+  //   vaddl q0, d4, d5
+  //   vmovl q1, d6
+  //   vmul  q0, q0, q1
+  SDValue N00 = SkipExtension(N0->getOperand(0).getNode(), DAG);
+  SDValue N01 = SkipExtension(N0->getOperand(1).getNode(), DAG);
+  EVT Op1VT = Op1.getValueType();
+  return DAG.getNode(N0->getOpcode(), DL, VT,
+                     DAG.getNode(NewOpc, DL, VT,
+                               DAG.getNode(ISD::BITCAST, DL, Op1VT, N00), Op1),
+                     DAG.getNode(NewOpc, DL, VT,
+                               DAG.getNode(ISD::BITCAST, DL, Op1VT, N01), Op1));
 }
 
 static SDValue