Revert "[Thumb] Teach ISel how to lower compares of AND bitmasks efficiently"

This reverts commit r281323. It caused chromium test failures and a selfhost failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281451 91177308-0d34-0410-b5e6-96231b3b80d8

Author: James Molloy

lib/Target/ARM/ARMBaseInstrInfo.cpp

@@ -2528,11 +2528,7 @@ bool ARMBaseInstrInfo::optimizeCompareInstr(
   case ARM::EORrr:
   case ARM::EORri:
   case ARM::t2EORrr:
-  case ARM::t2EORri:
-  case ARM::t2LSRri:
-  case ARM::t2LSRrr:
-  case ARM::t2LSLri:
-  case ARM::t2LSLrr: {
+  case ARM::t2EORri: {
     // Scan forward for the use of CPSR
     // When checking against MI: if it's a conditional code that requires
     // checking of the V bit or C bit, then this is not safe to do.

lib/Target/ARM/ARMISelDAGToDAG.cpp

@@ -244,8 +244,7 @@ class ARMDAGToDAGISel : public SelectionDAGISel {
   bool tryInlineAsm(SDNode *N);
 
   void SelectConcatVector(SDNode *N);
-  void SelectCMPZ(SDNode *N, bool &SwitchEQNEToPLMI);
-  
+
   bool trySMLAWSMULW(SDNode *N);
 
   void SelectCMP_SWAP(SDNode *N);
@@ -2694,83 +2693,6 @@ void ARMDAGToDAGISel::SelectConcatVector(SDNode *N) {
   ReplaceNode(N, createDRegPairNode(VT, N->getOperand(0), N->getOperand(1)));
 }
 
-static Optional<std::pair<unsigned, unsigned>>
-getContiguousRangeOfSetBits(const APInt &A) {
-  unsigned FirstOne = A.getBitWidth() - A.countLeadingZeros() - 1;
-  unsigned LastOne = A.countTrailingZeros();
-  if (A.countPopulation() != (FirstOne - LastOne + 1))
-    return Optional<std::pair<unsigned,unsigned>>();
-  return std::make_pair(FirstOne, LastOne);
-}
-
-void ARMDAGToDAGISel::SelectCMPZ(SDNode *N, bool &SwitchEQNEToPLMI) {
-  assert(N->getOpcode() == ARMISD::CMPZ);
-  SwitchEQNEToPLMI = false;
-  
-  if (!Subtarget->isThumb())
-    // FIXME: Work out whether it is profitable to do this in A32 mode - LSL and
-    // LSR don't exist as standalone instructions - they need the barrel shifter.
-    return;
-  // select (cmpz (and X, C), #0) -> (LSLS X) or (LSRS X) or (LSRS (LSLS X))
-  SDValue And = N->getOperand(0);
-  SDValue Zero = N->getOperand(1);
-  if (!isa<ConstantSDNode>(Zero) || !cast<ConstantSDNode>(Zero)->isNullValue() ||
-      And->getOpcode() != ISD::AND)
-    return;
-  SDValue X = And.getOperand(0);
-  auto C = dyn_cast<ConstantSDNode>(And.getOperand(1));
-
-  if (!C || !X->hasOneUse())
-    return;
-  auto Range = getContiguousRangeOfSetBits(C->getAPIntValue());
-  if (!Range)
-    return;
-
-  // There are several ways to lower this:
-  SDNode *NewN;
-  SDLoc dl(N);
-
-  auto EmitShift = [&](unsigned Opc, SDValue Src, unsigned Imm) -> SDNode* {
-    if (Subtarget->isThumb2()) {
-      Opc = (Opc == ARM::tLSLri) ? ARM::t2LSLri : ARM::t2LSRri;
-      SDValue Ops[] = { Src, CurDAG->getTargetConstant(Imm, dl, MVT::i32),
-                        getAL(CurDAG, dl), CurDAG->getRegister(0, MVT::i32),
-                        CurDAG->getRegister(0, MVT::i32) };
-      return CurDAG->getMachineNode(Opc, dl, MVT::i32, Ops);
-    } else {
-      SDValue Ops[] = {CurDAG->getRegister(ARM::CPSR, MVT::i32), Src,
-                       CurDAG->getTargetConstant(Imm, dl, MVT::i32),
-                       getAL(CurDAG, dl), CurDAG->getRegister(0, MVT::i32)};
-      return CurDAG->getMachineNode(Opc, dl, MVT::i32, Ops);
-    }
-  };
-  
-  if (Range->second == 0) {
-    //  1. Mask includes the LSB -> Simply shift the top N bits off
-    NewN = EmitShift(ARM::tLSLri, X, 31 - Range->first);
-    ReplaceNode(And.getNode(), NewN);
-  } else if (Range->first == 31) {
-    //  2. Mask includes the MSB -> Simply shift the bottom N bits off
-    NewN = EmitShift(ARM::tLSRri, X, Range->second);
-    ReplaceNode(And.getNode(), NewN);
-  } else if (Range->first == Range->second) {
-    //  3. Only one bit is set. We can shift this into the sign bit and use a
-    //     PL/MI comparison.
-    NewN = EmitShift(ARM::tLSLri, X, 31 - Range->first);
-    ReplaceNode(And.getNode(), NewN);
-
-    SwitchEQNEToPLMI = true;
-  } else if (!Subtarget->hasV6T2Ops()) {
-    //  4. Do a double shift to clear bottom and top bits, but only in
-    //     thumb-1 mode as in thumb-2 we can use UBFX.
-    NewN = EmitShift(ARM::tLSLri, X, 31 - Range->first);
-    NewN = EmitShift(ARM::tLSRri, SDValue(NewN, 0),
-                     Range->second + (31 - Range->first));
-    ReplaceNode(And.getNode(), NewN);
-  }
-
-}
-
 void ARMDAGToDAGISel::Select(SDNode *N) {
   SDLoc dl(N);
 
@@ -2998,7 +2920,6 @@ void ARMDAGToDAGISel::Select(SDNode *N) {
         return;
       }
     }
-
     break;
   }
   case ARMISD::VMOVRRD:
@@ -3189,27 +3110,9 @@ void ARMDAGToDAGISel::Select(SDNode *N) {
     assert(N2.getOpcode() == ISD::Constant);
     assert(N3.getOpcode() == ISD::Register);
 
-    unsigned CC = (unsigned) cast<ConstantSDNode>(N2)->getZExtValue();
-    
-    if (InFlag.getOpcode() == ARMISD::CMPZ) {
-      bool SwitchEQNEToPLMI;
-      SelectCMPZ(InFlag.getNode(), SwitchEQNEToPLMI);
-      InFlag = N->getOperand(4);
-
-      if (SwitchEQNEToPLMI) {
-        switch ((ARMCC::CondCodes)CC) {
-        default: llvm_unreachable("CMPZ must be either NE or EQ!");
-        case ARMCC::NE:
-          CC = (unsigned)ARMCC::MI;
-          break;
-        case ARMCC::EQ:
-          CC = (unsigned)ARMCC::PL;
-          break;
-        }
-      }
-    }
-
-    SDValue Tmp2 = CurDAG->getTargetConstant(CC, dl, MVT::i32);
+    SDValue Tmp2 = CurDAG->getTargetConstant(((unsigned)
+                               cast<ConstantSDNode>(N2)->getZExtValue()), dl,
+                               MVT::i32);
     SDValue Ops[] = { N1, Tmp2, N3, Chain, InFlag };
     SDNode *ResNode = CurDAG->getMachineNode(Opc, dl, MVT::Other,
                                              MVT::Glue, Ops);
@@ -3264,38 +3167,6 @@ void ARMDAGToDAGISel::Select(SDNode *N) {
     // Other cases are autogenerated.
     break;
   }
-
-  case ARMISD::CMOV: {
-    SDValue InFlag = N->getOperand(4);
-
-    if (InFlag.getOpcode() == ARMISD::CMPZ) {
-      bool SwitchEQNEToPLMI;
-      SelectCMPZ(InFlag.getNode(), SwitchEQNEToPLMI);
-
-      if (SwitchEQNEToPLMI) {
-        SDValue ARMcc = N->getOperand(2);
-        ARMCC::CondCodes CC =
-          (ARMCC::CondCodes)cast<ConstantSDNode>(ARMcc)->getZExtValue();
-
-        switch (CC) {
-        default: llvm_unreachable("CMPZ must be either NE or EQ!");
-        case ARMCC::NE:
-          CC = ARMCC::MI;
-          break;
-        case ARMCC::EQ:
-          CC = ARMCC::PL;
-          break;
-        }
-        SDValue NewARMcc = CurDAG->getConstant((unsigned)CC, dl, MVT::i32);
-        SDValue Ops[] = {N->getOperand(0), N->getOperand(1), NewARMcc,
-                         N->getOperand(3), N->getOperand(4)};
-        CurDAG->MorphNodeTo(N, ARMISD::CMOV, N->getVTList(), Ops);
-      }
-
-    }
-    // Other cases are autogenerated.
-    break;
-  }
 
   case ARMISD::VZIP: {
     unsigned Opc = 0;

test/CodeGen/ARM/and-cmpz.ll

@@ -28,10 +28,12 @@ tailrecurse:                                      ; preds = %sw.bb, %entry
 ; ARM:      ands {{r[0-9]+}}, {{r[0-9]+}}, #3
 ; ARM-NEXT: beq
 
-; THUMB:      lsls r[[R0:[0-9]+]], r{{.*}}, #30
+; THUMB:      movs r[[R0:[0-9]+]], #3
+; THUMB-NEXT: ands r[[R0]], r
+; THUMB-NEXT: cmp r[[R0]], #0
 ; THUMB-NEXT: beq
 
-; T2:      lsls r[[R0:[0-9]+]], r{{.*}}, #30
+; T2:      ands {{r[0-9]+}}, {{r[0-9]+}}, #3
 ; T2-NEXT: beq
 
   %and = and i32 %0, 3
@@ -91,7 +93,7 @@ entry:
   %1 = load i8, i8* %0, align 1
   %2 = zext i8 %1 to i32
 ; ARM: ands
-; THUMB: lsls
+; THUMB: ands
 ; T2: ands
 ; V8: ands
 ; V8-NEXT: beq
@@ -148,9 +150,10 @@ define i32 @test_tst_assessment(i1 %lhs, i1 %rhs) {
   %rhs32 = zext i1 %rhs to i32
   %diff = sub nsw i32 %lhs32, %rhs32
 ; ARM: tst r1, #1
-; THUMB: lsls r1, r1, #31
-; T2: lsls r1, r1, #31
-; V8: lsls r1, r1, #31
+; THUMB: movs [[RTMP:r[0-9]+]], #1
+; THUMB: tst r1, [[RTMP]]
+; T2: tst.w r1, #1
+; V8: tst.w r1, #1
   ret i32 %diff
 }
 

test/CodeGen/ARM/arm-and-tst-peephole.ll

@@ -638,12 +638,12 @@ declare double @llvm.pow.f64(double, double)
 ; during PEI with shrink-wrapping enable.
 ; CHECK-LABEL: debug_info:
 ;
-; ENABLE: {{tst  r2, #1|lsls r1, r2, #31}}
+; ENABLE: tst{{(\.w)?}}  r2, #1
 ; ENABLE-NEXT: beq      [[BB13:LBB[0-9_]+]]
 ;
 ; CHECK: push
 ;
-; DISABLE: {{tst  r2, #1|lsls r1, r2, #31}}
+; DISABLE: tst{{(\.w)?}}  r2, #1
 ; DISABLE-NEXT: beq      [[BB13:LBB[0-9_]+]]
 ;
 ; CHECK: bl{{x?}} _pow

test/CodeGen/ARM/arm-shrink-wrapping.ll

@@ -120,7 +120,7 @@ if.end:                                           ; preds = %entry
   br i1 %tobool2, label %if.end5, label %if.then3
 
 if.then3:                                         ; preds = %if.end
-; CHECKT2D: bmi.w _b
+; CHECKT2D: bne.w _b
   %call4 = tail call i32 @b(i32 %x) nounwind
   br label %return
 

test/CodeGen/ARM/call-tc.ll

@@ -3,7 +3,7 @@ target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-
 target triple = "thumbv7-apple-macosx10.6.7"
 
 ;CHECK: 	vadd.f32	q4, q8, q8
-;CHECK-NEXT: Ltmp
+;CHECK-NEXT: Ltmp1
 ;CHECK-NEXT: LBB0_1
 
 ;CHECK:@DEBUG_VALUE: x <- %Q4{{$}}

test/CodeGen/ARM/debug-info-branch-folding.ll

@@ -650,14 +650,11 @@ define i1 @beq_to_bx(i32* %y, i32 %head) {
 
 ; CHECK: tst r3, r4
 ; ENABLE-NEXT: pop {r4}
-; ENABLE-NEXT: mov r12, r{{.*}}
-; ENABLE-NEXT: pop {r0}
-; ENABLE-NEXT: mov lr, r0
-; ENABLE-NEXT: mov r0, r12
+; ENABLE-NEXT: pop {r3}
+; ENABLE-NEXT: mov lr, r3
 ; CHECK-NEXT: beq [[EXIT_LABEL]]
 
 ; CHECK: str r1, [r2]
-; CHECK: str r3, [r2]
 ; CHECK-NEXT: movs r0, #0
 ; CHECK-NEXT: [[EXIT_LABEL]]: @ %cleanup
 ; ENABLE-NEXT: bx lr
@@ -678,7 +675,6 @@ if.end:
 
 if.end4:
   store i32 %head, i32* %y, align 4
-  store volatile i32 %z, i32* %y, align 4
   br label %cleanup
 
 cleanup:

test/CodeGen/Thumb/thumb-shrink-wrapping.ll

@@ -259,9 +259,9 @@ define i64 @bitcast_d_to_i(double %a) {
 
 define float @select_f(float %a, float %b, i1 %c) {
 ; CHECK-LABEL: select_f:
-; NONE: lsls    r2, r2, #31
+; NONE: tst.w   r2, #1
 ; NONE: moveq   r0, r1
-; HARD: lsls    r0, r0, #31
+; HARD: tst.w   r0, #1
 ; VFP4-ALL: vmovne.f32      s1, s0
 ; VFP4-ALL: vmov.f32        s0, s1
 ; FP-ARMv8: vseleq.f32 s0, s1, s0
@@ -271,18 +271,18 @@ define float @select_f(float %a, float %b, i1 %c) {
 
 define double @select_d(double %a, double %b, i1 %c) {
 ; CHECK-LABEL: select_d:
-; NONE: ldr{{(.w)?}}     [[REG:r[0-9]+]], [sp]
-; NONE: lsls{{(.w)?}}    [[REG]], [[REG]], #31
+; NONE: ldr.w   [[REG:r[0-9]+]], [sp]
+; NONE: ands    [[REG]], [[REG]], #1
 ; NONE: moveq   r0, r2
 ; NONE: moveq   r1, r3
-; SP: lsls r0, r0, #31
+; SP: ands r0, r0, #1
 ; SP-DAG: vmov [[ALO:r[0-9]+]], [[AHI:r[0-9]+]], d0
 ; SP-DAG: vmov [[BLO:r[0-9]+]], [[BHI:r[0-9]+]], d1
 ; SP: itt ne
 ; SP-DAG: movne [[BLO]], [[ALO]]
 ; SP-DAG: movne [[BHI]], [[AHI]]
 ; SP: vmov d0, [[BLO]], [[BHI]]
-; DP: lsls   r0, r0, #31
+; DP: tst.w   r0, #1
 ; VFP4-DP: vmovne.f64      d1, d0
 ; VFP4-DP: vmov.f64        d0, d1
 ; FP-ARMV8: vseleq.f64      d0, d1, d0