Commit f36007e8 authored by Jessica Paquette's avatar Jessica Paquette
Browse files

[GlobalISel] Implement computeKnownBits for G_SEXT_INREG 

Just use the existing `Known.sextInReg` implementation.

- Update KnownBitsTest.cpp.
- Update combine-redundant-and.mir for a more concrete example.

Differential Revision: https://reviews.llvm.org/D95484
parent 0554541b

llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp

+6 −0
Original line number Diff line number Diff line
@@ -347,6 +347,12 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known, 
    Known = Known.sext(BitWidth);

    break;

  }

  case TargetOpcode::G_SEXT_INREG: {

    computeKnownBitsImpl(MI.getOperand(1).getReg(), Known, DemandedElts,

                         Depth + 1);

    Known = Known.sextInReg(MI.getOperand(2).getImm());

    break;

  }

  case TargetOpcode::G_ANYEXT: {

    computeKnownBitsImpl(MI.getOperand(1).getReg(), Known, DemandedElts,

                         Depth + 1);

llvm/test/CodeGen/AMDGPU/GlobalISel/combine-redundant-and.mir

+21 −0
Original line number Diff line number Diff line
@@ -142,3 +142,24 @@ body: | 
    $sgpr0 = COPY %6(s32)

    SI_RETURN_TO_EPILOG implicit $sgpr0

...

---

name:            test_sext_inreg

tracksRegLiveness: true

body:             |

  bb.0:

    ; CHECK-LABEL: name: test_sext_inreg

    ; CHECK: %cst_1:_(s32) = G_CONSTANT i32 -5

    ; CHECK: $sgpr0 = COPY %cst_1(s32)

    ; CHECK: SI_RETURN_TO_EPILOG implicit $sgpr0

    %cst_1:_(s32) = G_CONSTANT i32 -5



    ; 000 ... 1011

    %cst_11:_(s32) = G_CONSTANT i32 11



    ; Sext from the 4th bit -> 111 ... 1011 = -5

    %sext_inreg_11:_(s32) = G_SEXT_INREG %cst_11, 4



    %and:_(s32) = G_AND %cst_1(s32), %sext_inreg_11(s32)

    $sgpr0 = COPY %and(s32)

    SI_RETURN_TO_EPILOG implicit $sgpr0

...

llvm/unittests/CodeGen/GlobalISel/KnownBitsTest.cpp

+72 −0
Original line number Diff line number Diff line
@@ -701,6 +701,78 @@ TEST_F(AArch64GISelMITest, TestKnownBitsExt) { 
  EXPECT_EQ((uint64_t)0xfffffffe, Res.Zero.getZExtValue());

}



TEST_F(AArch64GISelMITest, TestKnownBitsSextInReg) {

  StringRef MIRString = R"(

   ; 000...0001

   %one:_(s32) = G_CONSTANT i32 1



   ; 000...0010

   %two:_(s32) = G_CONSTANT i32 2



   ; 000...1010

   %ten:_(s32) = G_CONSTANT i32 10



   ; ???...????

   %w0:_(s32) = COPY $w0



   ; ???...?1?

   %or:_(s32) = G_OR %w0, %two



   ; All bits are known.

   %inreg1:_(s32) = G_SEXT_INREG %one, 1

   %copy_inreg1:_(s32) = COPY %inreg1



   ; All bits unknown

   %inreg2:_(s32) = G_SEXT_INREG %or, 1

   %copy_inreg2:_(s32) = COPY %inreg2



   ; Extending from the only (known) set bit

   ; 111...11?

   %inreg3:_(s32) = G_SEXT_INREG %or, 2

   %copy_inreg3:_(s32) = COPY %inreg3



   ; Extending from a known set bit, overwriting all of the high set bits.

   ; 111...1110

   %inreg4:_(s32) = G_SEXT_INREG %ten, 2

   %copy_inreg4:_(s32) = COPY %inreg4



)";

  setUp(MIRString);

  if (!TM)

    return;

  GISelKnownBits Info(*MF);

  KnownBits Res;

  auto GetKB = [&](unsigned Idx) {

    Register CopyReg = Copies[Idx];

    auto *Copy = MRI->getVRegDef(CopyReg);

    return Info.getKnownBits(Copy->getOperand(1).getReg());

  };



  // Every bit is known to be a 1.

  Res = GetKB(Copies.size() - 4);

  EXPECT_EQ(32u, Res.getBitWidth());

  EXPECT_TRUE(Res.isAllOnes());



  // All bits are unknown

  Res = GetKB(Copies.size() - 3);

  EXPECT_EQ(32u, Res.getBitWidth());

  EXPECT_TRUE(Res.isUnknown());



  // Extending from the only known set bit

  // 111...11?

  Res = GetKB(Copies.size() - 2);

  EXPECT_EQ(32u, Res.getBitWidth());

  EXPECT_EQ(0xFFFFFFFEu, Res.One.getZExtValue());

  EXPECT_EQ(0u, Res.Zero.getZExtValue());



  // Extending from a known set bit, overwriting all of the high set bits.

  // 111...1110

  Res = GetKB(Copies.size() - 1);

  EXPECT_EQ(32u, Res.getBitWidth());

  EXPECT_EQ(0xFFFFFFFEu, Res.One.getZExtValue());

  EXPECT_EQ(1u, Res.Zero.getZExtValue());

}



TEST_F(AArch64GISelMITest, TestKnownBitsMergeValues) {

  StringRef MIRString = R"(

   %val0:_(s16) = G_CONSTANT i16 35224