Revert "[FastISel][AArch64] Fold bit test and branch into TBZ and TBNZ."

Reverting it until I have time to investigate a regression.

llvm-svn: 218035

1 files changed, 8 insertions, 32 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64FastISel.cpp b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
index 88038ff0844..1ba5ba5de70 100644
--- a/llvm/lib/Target/AArch64/AArch64FastISel.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
@@ -1860,7 +1860,7 @@ static AArch64CC::CondCode getCompareCC(CmpInst::Predicate Pred) {
 
 /// \brief Check if the comparison against zero and the following branch can be
 /// folded into a single instruction (CBZ or CBNZ).
-static bool canFoldZeroCheckIntoBranch(const CmpInst *CI) {
+static bool canFoldZeroIntoBranch(const CmpInst *CI) {
   CmpInst::Predicate Predicate = CI->getPredicate();
   if ((Predicate != CmpInst::ICMP_EQ) && (Predicate != CmpInst::ICMP_NE))
     return false;
@@ -1918,7 +1918,7 @@ bool AArch64FastISel::selectBranch(const Instruction *I) {
       }
 
       // Try to optimize comparisons against zero.
-      if (canFoldZeroCheckIntoBranch(CI)) {
+      if (canFoldZeroIntoBranch(CI)) {
         const Value *LHS = CI->getOperand(0);
         const Value *RHS = CI->getOperand(1);
 
@@ -1927,33 +1927,12 @@ bool AArch64FastISel::selectBranch(const Instruction *I) {
           if (C->isNullValue())
             std::swap(LHS, RHS);
 
-        int TestBit = -1;
-        if (const auto *AI = dyn_cast<BinaryOperator>(LHS))
-          if (AI->getOpcode() == Instruction::And) {
-            const Value *AndLHS = AI->getOperand(0);
-            const Value *AndRHS = AI->getOperand(1);
-
-            if (const auto *C = dyn_cast<ConstantInt>(AndLHS))
-              if (C->getValue().isPowerOf2())
-                std::swap(AndLHS, AndRHS);
-
-            if (const auto *C = dyn_cast<ConstantInt>(AndRHS))
-              if (C->getValue().isPowerOf2()) {
-                TestBit = C->getValue().logBase2();
-                LHS = AndLHS;
-              }
-          }
-
-        static const unsigned OpcTable[2][2][2] = {
-          { {AArch64::CBZW,  AArch64::CBZX },
-            {AArch64::CBNZW, AArch64::CBNZX} },
-          { {AArch64::TBZW,  AArch64::TBZX },
-            {AArch64::TBNZW, AArch64::TBNZX} }
+        static const unsigned OpcTable[2][2] = {
+          {AArch64::CBZW,  AArch64::CBZX }, {AArch64::CBNZW, AArch64::CBNZX}
         };
-        bool IsBitTest = TestBit != -1;
         bool IsCmpNE = Predicate == CmpInst::ICMP_NE;
         bool Is64Bit = LHS->getType()->isIntegerTy(64);
-        unsigned Opc = OpcTable[IsBitTest][IsCmpNE][Is64Bit];
+        unsigned Opc = OpcTable[IsCmpNE][Is64Bit];
 
         unsigned SrcReg = getRegForValue(LHS);
         if (!SrcReg)
@@ -1961,12 +1940,9 @@ bool AArch64FastISel::selectBranch(const Instruction *I) {
         bool SrcIsKill = hasTrivialKill(LHS);
 
         // Emit the combined compare and branch instruction.
-        MachineInstrBuilder MIB =
-            BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc))
-                .addReg(SrcReg, getKillRegState(SrcIsKill));
-        if (IsBitTest)
-          MIB.addImm(TestBit);
-        MIB.addMBB(TBB);
+        BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc))
+            .addReg(SrcReg, getKillRegState(SrcIsKill))
+            .addMBB(TBB);
 
         // Obtain the branch weight and add the TrueBB to the successor list.
         uint32_t BranchWeight = 0;