From 30fb13f97a197823f66da4df98625a9b3585ece9 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 13 Dec 2010 20:32:54 +0000
Subject: [PATCH] Generalize BFI isel lowering a bit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121714 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelLowering.cpp | 64 ++++++++++++++++--------------
 1 file changed, 35 insertions(+), 29 deletions(-)

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index f4a12ed77c5..3af04f104ba 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -4713,57 +4713,43 @@ static SDValue PerformORCombine(SDNode *N,
   if (VT != MVT::i32)
     return SDValue();
 
+  SDValue N00 = N0.getOperand(0);
 
   // The value and the mask need to be constants so we can verify this is
   // actually a bitfield set. If the mask is 0xffff, we can do better
   // via a movt instruction, so don't use BFI in that case.
-  ConstantSDNode *C = dyn_cast<ConstantSDNode>(N0.getOperand(1));
-  if (!C)
+  SDValue MaskOp = N0.getOperand(1);
+  ConstantSDNode *MaskC = dyn_cast<ConstantSDNode>(MaskOp);
+  if (!MaskC)
     return SDValue();
-  unsigned Mask = C->getZExtValue();
+  unsigned Mask = MaskC->getZExtValue();
   if (Mask == 0xffff)
     return SDValue();
   SDValue Res;
   // Case (1): or (and A, mask), val => ARMbfi A, val, mask
-  if ((C = dyn_cast<ConstantSDNode>(N1))) {
-    unsigned Val = C->getZExtValue();
+  ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
+  if (N1C) {
+    unsigned Val = N1C->getZExtValue();
     if ((Val & ~Mask) != Val)
       return SDValue();
 
     if (ARM::isBitFieldInvertedMask(Mask)) {
       Val >>= CountTrailingZeros_32(~Mask);
 
-      Res = DAG.getNode(ARMISD::BFI, DL, VT, N0.getOperand(0),
+      Res = DAG.getNode(ARMISD::BFI, DL, VT, N00,
                         DAG.getConstant(Val, MVT::i32),
                         DAG.getConstant(Mask, MVT::i32));
 
       // Do not add new nodes to DAG combiner worklist.
       DCI.CombineTo(N, Res, false);
-    } else if (N0.getOperand(0).getOpcode() == ISD::SHL &&
-               isa<ConstantSDNode>(N0.getOperand(0).getOperand(1)) &&
-               ARM::isBitFieldInvertedMask(~Mask)) {
-      // Case (3): or (and (shl A, #shamt), mask), B => ARMbfi B, A, ~mask
-      // where lsb(mask) == #shamt
-      SDValue ShAmt = N0.getOperand(0).getOperand(1);
-      unsigned ShAmtC = cast<ConstantSDNode>(ShAmt)->getZExtValue();
-      unsigned LSB = CountTrailingZeros_32(Mask);
-      if (ShAmtC != LSB)
-        return SDValue();
-      //unsigned Width = (32 - CountLeadingZeros_32(Mask)) - LSB;
-
-      Res = DAG.getNode(ARMISD::BFI, DL, VT, N1,
-                        N0.getOperand(0).getOperand(0),
-                        DAG.getConstant(~Mask, MVT::i32));
-
-      // Do not add new nodes to DAG combiner worklist.
-      DCI.CombineTo(N, Res, false);
+      return SDValue();
     }
   } else if (N1.getOpcode() == ISD::AND) {
     // case (2) or (and A, mask), (and B, mask2) => ARMbfi A, (lsr B, amt), mask
-    C = dyn_cast<ConstantSDNode>(N1.getOperand(1));
-    if (!C)
+    ConstantSDNode *N11C = dyn_cast<ConstantSDNode>(N1.getOperand(1));
+    if (!N11C)
       return SDValue();
-    unsigned Mask2 = C->getZExtValue();
+    unsigned Mask2 = N11C->getZExtValue();
 
     if (ARM::isBitFieldInvertedMask(Mask) &&
         ARM::isBitFieldInvertedMask(~Mask2) &&
@@ -4777,10 +4763,11 @@ static SDValue PerformORCombine(SDNode *N,
       unsigned lsb = CountTrailingZeros_32(Mask2);
       Res = DAG.getNode(ISD::SRL, DL, VT, N1.getOperand(0),
                         DAG.getConstant(lsb, MVT::i32));
-      Res = DAG.getNode(ARMISD::BFI, DL, VT, N0.getOperand(0), Res,
+      Res = DAG.getNode(ARMISD::BFI, DL, VT, N00, Res,
                         DAG.getConstant(Mask, MVT::i32));
       // Do not add new nodes to DAG combiner worklist.
       DCI.CombineTo(N, Res, false);
+      return SDValue();
     } else if (ARM::isBitFieldInvertedMask(~Mask) &&
                ARM::isBitFieldInvertedMask(Mask2) &&
                (CountPopulation_32(~Mask) == CountPopulation_32(Mask2))) {
@@ -4791,15 +4778,34 @@ static SDValue PerformORCombine(SDNode *N,
         return SDValue();
       // 2b
       unsigned lsb = CountTrailingZeros_32(Mask);
-      Res = DAG.getNode(ISD::SRL, DL, VT, N0.getOperand(0),
+      Res = DAG.getNode(ISD::SRL, DL, VT, N00,
                         DAG.getConstant(lsb, MVT::i32));
       Res = DAG.getNode(ARMISD::BFI, DL, VT, N1.getOperand(0), Res,
                                 DAG.getConstant(Mask2, MVT::i32));
       // Do not add new nodes to DAG combiner worklist.
       DCI.CombineTo(N, Res, false);
+      return SDValue();
     }
   }
 
+  if (DAG.MaskedValueIsZero(N1, MaskC->getAPIntValue()) &&
+      N00.getOpcode() == ISD::SHL && isa<ConstantSDNode>(N00.getOperand(1)) &&
+      ARM::isBitFieldInvertedMask(~Mask)) {
+    // Case (3): or (and (shl A, #shamt), mask), B => ARMbfi B, A, ~mask
+    // where lsb(mask) == #shamt and masked bits of B are known zero.
+    SDValue ShAmt = N00.getOperand(1);
+    unsigned ShAmtC = cast<ConstantSDNode>(ShAmt)->getZExtValue();
+    unsigned LSB = CountTrailingZeros_32(Mask);
+    if (ShAmtC != LSB)
+      return SDValue();
+
+    Res = DAG.getNode(ARMISD::BFI, DL, VT, N1, N00.getOperand(0),
+                      DAG.getConstant(~Mask, MVT::i32));
+
+    // Do not add new nodes to DAG combiner worklist.
+    DCI.CombineTo(N, Res, false);
+  }
+
   return SDValue();
 }