Commit 80f974e4 authored by guopeilin's avatar guopeilin Committed by Tom Stellard
Browse files

[AArch64][GlobalISel] Use ZExtValue for zext(xor) when invert tb(n)z 

Currently, we use SExtValue to decide whether to invert tbz or tbnz.
However, for the case zext (xor x, c), we should use ZExt rather
than SExt otherwise we will generate totally opposite branches.

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D108755

(cherry picked from commit 5f48c144)
parent 5b95eb0b

llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp

+10 −2
Original line number Diff line number Diff line
@@ -1301,6 +1301,7 @@ static AArch64CC::CondCode changeICMPPredToAArch64CC(CmpInst::Predicate P) { 
static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,

                              MachineRegisterInfo &MRI) {

  assert(Reg.isValid() && "Expected valid register!");

  bool HasZext = false;

  while (MachineInstr *MI = getDefIgnoringCopies(Reg, MRI)) {

    unsigned Opc = MI->getOpcode();
@@ -1314,6 +1315,9 @@ static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert, 
    // on the truncated x is the same as the bit number on x.

    if (Opc == TargetOpcode::G_ANYEXT || Opc == TargetOpcode::G_ZEXT ||

        Opc == TargetOpcode::G_TRUNC) {

      if (Opc == TargetOpcode::G_ZEXT)

        HasZext = true;



      Register NextReg = MI->getOperand(1).getReg();

      // Did we find something worth folding?

      if (!NextReg.isValid() || !MRI.hasOneNonDBGUse(NextReg))
@@ -1342,8 +1346,12 @@ static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert, 
        std::swap(ConstantReg, TestReg);

        VRegAndVal = getConstantVRegValWithLookThrough(ConstantReg, MRI);

      }

      if (VRegAndVal)

      if (VRegAndVal) {

        if (HasZext)

          C = VRegAndVal->Value.getZExtValue();

        else

          C = VRegAndVal->Value.getSExtValue();

      }

      break;

    }

    case TargetOpcode::G_ASHR:

llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir

+32 −0
Original line number Diff line number Diff line
@@ -117,6 +117,38 @@ body: | 
    RET_ReallyLR

...

---

name:            dont_flip_eq_zext

alignment:       4

legalized:       true

regBankSelected: true

tracksRegLiveness: true

body:             |

  ; CHECK-LABEL: name: dont_flip_eq_zext

  ; CHECK: bb.0:

  ; CHECK:   successors: %bb.0(0x40000000), %bb.1(0x40000000)

  ; CHECK:   [[COPY:%[0-9]+]]:gpr32 = COPY $wzr

  ; CHECK:   [[SUBREG_TO_REG:%[0-9]+]]:gpr64all = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32

  ; CHECK:   [[COPY1:%[0-9]+]]:gpr64 = COPY [[SUBREG_TO_REG]]

  ; CHECK:   TBNZX [[COPY1]], 63, %bb.1

  ; CHECK:   B %bb.0

  ; CHECK: bb.1:

  ; CHECK:   RET_ReallyLR

  bb.0:

    successors: %bb.0(0x40000000), %bb.1(0x40000000)



    %1:gpr(s32) = G_CONSTANT i32 0

    %3:gpr(s32) = G_CONSTANT i32 -1

    %4:gpr(s32) = G_XOR %1, %3

    %5:gpr(s64) = G_ZEXT %4(s32)

    %15:gpr(s64) = G_CONSTANT i64 0

    %13:gpr(s32) = G_ICMP intpred(slt), %5(s64), %15

    %7:gpr(s1) = G_TRUNC %13(s32)

    G_BRCOND %7(s1), %bb.1

    G_BR %bb.0

  bb.1:

    RET_ReallyLR

...

---

name:            dont_flip_ne

alignment:       4

legalized:       true