Revert "[ARM] Combine CMOV into BFI where possible"

This reverts commit r252057, as it broke ARM self-hosting buildbots, probably
due to a code-gen fault.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252460 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index da8ecfa1102b4b4d9cfc2823b93b72e9a46c1f6e..8f9ca96e5d95d922d24a89f8aea91965f3f4924f 100644 (file)
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -10221,114 +10221,6 @@ static SDValue PerformExtendCombine(SDNode *N, SelectionDAG &DAG,
   return SDValue();
 }
 
-static void computeKnownBits(SelectionDAG &DAG, SDValue Op, APInt &KnownZero,
-                             APInt &KnownOne) {
-  if (Op.getOpcode() == ARMISD::BFI) {
-    // Conservatively, we can recurse down the first operand
-    // and just mask out all affected bits.
-    computeKnownBits(DAG, Op.getOperand(0), KnownZero, KnownOne);
-
-    // The operand to BFI is already a mask suitable for removing the bits it
-    // sets.
-    ConstantSDNode *CI = cast<ConstantSDNode>(Op.getOperand(2));
-    APInt Mask = CI->getAPIntValue();
-    KnownZero &= Mask;
-    KnownOne &= Mask;
-    return;
-  }
-  if (Op.getOpcode() == ARMISD::CMOV) {
-    APInt KZ2(KnownZero.getBitWidth(), 0);
-    APInt KO2(KnownOne.getBitWidth(), 0);
-    computeKnownBits(DAG, Op.getOperand(1), KnownZero, KnownOne);
-    computeKnownBits(DAG, Op.getOperand(2), KZ2, KO2);
-
-    KnownZero &= KZ2;
-    KnownOne &= KO2;
-    return;
-  }
-  return DAG.computeKnownBits(Op, KnownZero, KnownOne);
-}
-
-SDValue ARMTargetLowering::PerformCMOVToBFICombine(SDNode *CMOV, SelectionDAG &DAG) const {
-  // If we have a CMOV, OR and AND combination such as:
-  //   if (x & CN)
-  //     y |= CM;
-  //
-  // And:
-  //   * CN is a single bit;
-  //   * All bits covered by CM are known zero in y
-  //
-  // Then we can convert this into a sequence of BFI instructions. This will
-  // always be a win if CM is a single bit, will always be no worse than the
-  // TST&OR sequence if CM is two bits, and for thumb will be no worse if CM is
-  // three bits (due to the extra IT instruction).
-
-  SDValue Op0 = CMOV->getOperand(0);
-  SDValue Op1 = CMOV->getOperand(1);
-  SDValue CmpZ = CMOV->getOperand(4);
-
-  assert(CmpZ->getOpcode() == ARMISD::CMPZ);
-  SDValue And = CmpZ->getOperand(0);
-  if (And->getOpcode() != ISD::AND)
-    return SDValue();
-  ConstantSDNode *AndC = dyn_cast<ConstantSDNode>(And->getOperand(1));
-  if (!AndC || !AndC->getAPIntValue().isPowerOf2())
-    return SDValue();
-  SDValue X = And->getOperand(0);
-
-  // Canonicalize so that the OR is on the left.
-  if (Op1->getOpcode() == ISD::OR)
-    std::swap(Op0, Op1);
-  if (Op0->getOpcode() != ISD::OR)
-    return SDValue();
-
-  ConstantSDNode *OrC = dyn_cast<ConstantSDNode>(Op0->getOperand(1));
-  if (!OrC)
-    return SDValue();
-  SDValue Y = Op0->getOperand(0);
-
-  if (Op1 != Y)
-    return SDValue();
-
-  // Now, is it profitable to continue?
-  APInt OrCI = OrC->getAPIntValue();
-  unsigned Heuristic = Subtarget->isThumb() ? 3 : 2;
-  if (OrCI.countPopulation() > Heuristic)
-    return SDValue();
-
-  // Lastly, can we determine that the bits defined by OrCI
-  // are zero in Y?
-  APInt KnownZero, KnownOne;
-  computeKnownBits(DAG, Y, KnownZero, KnownOne);
-  if ((OrCI & KnownZero) != OrCI)
-    return SDValue();
-
-  // OK, we can do the combine.
-  SDValue V = Y;
-  SDLoc dl(X);
-  EVT VT = X.getValueType();
-  unsigned BitInX = AndC->getAPIntValue().logBase2();
-  
-  if (BitInX != 0) {
-    // We must shift X first.
-    X = DAG.getNode(ISD::SRL, dl, VT, X,
-                    DAG.getConstant(BitInX, dl, VT));
-  }
-
-  for (unsigned BitInY = 0, NumActiveBits = OrCI.getActiveBits();
-       BitInY < NumActiveBits; ++BitInY) {
-    if (OrCI[BitInY] == 0)
-      continue;
-    APInt Mask(VT.getSizeInBits(), 0);
-    Mask.setBit(BitInY);
-    V = DAG.getNode(ARMISD::BFI, dl, VT, V, X,
-                    // Confusingly, the operand is an *inverted* mask.
-                    DAG.getConstant(~Mask, dl, VT));
-  }
-
-  return V;
-}
-
 /// PerformCMOVCombine - Target-specific DAG combining for ARMISD::CMOV.
 SDValue
 ARMTargetLowering::PerformCMOVCombine(SDNode *N, SelectionDAG &DAG) const {
@@ -10347,13 +10239,6 @@ ARMTargetLowering::PerformCMOVCombine(SDNode *N, SelectionDAG &DAG) const {
   ARMCC::CondCodes CC =
     (ARMCC::CondCodes)cast<ConstantSDNode>(ARMcc)->getZExtValue();
 
-  // BFI is only available on V6T2+.
-  if (!Subtarget->isThumb1Only() && Subtarget->hasV6T2Ops()) {
-    SDValue R = PerformCMOVToBFICombine(N, DAG);
-    if (R)
-      return R;
-  }
-
   // Simplify
   //   mov     r1, r0
   //   cmp     r1, x

diff --git a/lib/Target/ARM/ARMISelLowering.h b/lib/Target/ARM/ARMISelLowering.h
index 534f92b941c3a7c813728dfe82fe31a6823f9484..df4b6553ab57f9dace886c6fce48b86c96e8601c 100644 (file)
--- a/lib/Target/ARM/ARMISelLowering.h
+++ b/lib/Target/ARM/ARMISelLowering.h
@@ -260,7 +260,6 @@ namespace llvm {
                                        SDNode *Node) const override;
 
     SDValue PerformCMOVCombine(SDNode *N, SelectionDAG &DAG) const;
-    SDValue PerformCMOVToBFICombine(SDNode *N, SelectionDAG &DAG) const;
     SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
     bool isDesirableToTransformToIntegerOp(unsigned Opc, EVT VT) const override;

diff --git a/test/CodeGen/ARM/bfi.ll b/test/CodeGen/ARM/bfi.ll
index 46653c3e7be322a54113a9a7c06c13f67a6dbb4c..0661960d1ae002878220312b8945fddec27fdc19 100644 (file)
--- a/test/CodeGen/ARM/bfi.ll
+++ b/test/CodeGen/ARM/bfi.ll
@@ -74,26 +74,3 @@ entry:
   %or = or i32 %shl, %and
   ret i32 %or
 }
-
-define i32 @f7(i32 %x, i32 %y) {
-; CHECK-LABEL: f7:
-; CHECK: bfi r1, r0, #4, #1
-  %y2 = and i32 %y, 4294967040 ; 0xFFFFFF00
-  %and = and i32 %x, 4
-  %or = or i32 %y2, 16
-  %cmp = icmp ne i32 %and, 0
-  %sel = select i1 %cmp, i32 %or, i32 %y2
-  ret i32 %sel
-}
-
-define i32 @f8(i32 %x, i32 %y) {
-; CHECK-LABEL: f8:
-; CHECK: bfi r1, r0, #4, #1
-; CHECK: bfi r1, r0, #5, #1
-  %y2 = and i32 %y, 4294967040 ; 0xFFFFFF00
-  %and = and i32 %x, 4
-  %or = or i32 %y2, 48
-  %cmp = icmp ne i32 %and, 0
-  %sel = select i1 %cmp, i32 %or, i32 %y2
-  ret i32 %sel
-}