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[GlobalISel] add G_ROTL, G_ROTR to computeKnownBits #166365

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[GlobalISel] add G_ROTL, G_ROTR to computeKnownBits #166365

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491b20b
[GlobalISel] add G_ROTL, G_ROTR to computeKnownBits
mooori Oct 27, 2025
5767a7a
Address review comments
mooori Nov 5, 2025
1df5c4a
Merge remote-tracking branch 'upstream/main' into gisel-knownbits-rotlr
mooori Nov 5, 2025
c57ff7a
Address review comment
mooori Nov 5, 2025
9de3a8c
Merge remote-tracking branch 'upstream/main' into gisel-knownbits-rotlr
mooori Nov 5, 2025
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21 changes: 21 additions & 0 deletions llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -483,6 +483,27 @@ void GISelValueTracking::computeKnownBitsImpl(Register R, KnownBits &Known,
Known = KnownBits::shl(LHSKnown, RHSKnown);
break;
}
case TargetOpcode::G_ROTL:
case TargetOpcode::G_ROTR: {
MachineInstr *AmtOpMI = MRI.getVRegDef(MI.getOperand(2).getReg());
if (!AmtOpMI)
break;
auto MaybeAmtOp = isConstantOrConstantSplatVector(*AmtOpMI, MRI);
if (MaybeAmtOp.has_value()) {
unsigned Amt = MaybeAmtOp.value().urem(BitWidth);

Register SrcReg = MI.getOperand(1).getReg();
computeKnownBitsImpl(SrcReg, Known, DemandedElts, Depth + 1);

// Canonicalize to ROTR.
if (Opcode == TargetOpcode::G_ROTL && Amt != 0)
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@jayfoad jayfoad Nov 5, 2025

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Simpler:

Suggested change
if (Opcode == TargetOpcode::G_ROTL && Amt != 0)
if (Opcode == TargetOpcode::G_ROTL)

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@arsenm arsenm Nov 5, 2025

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The DAG version has the 0 check

Amt = BitWidth - Amt;

Known.Zero = Known.Zero.rotr(Amt);
Known.One = Known.One.rotr(Amt);
}
break;
}
case TargetOpcode::G_INTTOPTR:
case TargetOpcode::G_PTRTOINT:
if (DstTy.isVector())
Expand Down
270 changes: 270 additions & 0 deletions llvm/test/CodeGen/AArch64/GlobalISel/knownbits-rotl-rotr.mir
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@@ -0,0 +1,270 @@
# NOTE: Assertions have been autogenerated by utils/update_givaluetracking_test_checks.py UTC_ARGS: --version 5
# RUN: llc -mtriple aarch64 -passes="print<gisel-value-tracking>" %s -o - 2>&1 | FileCheck %s

---
name: Cst
body: |
bb.1:
; CHECK-LABEL: name: @Cst
; CHECK-NEXT: %0:_ KnownBits:11100010 SignBits:3
; CHECK-NEXT: %1:_ KnownBits:00000010 SignBits:6
; CHECK-NEXT: %2:_ KnownBits:10111000 SignBits:1
%0:_(s8) = G_CONSTANT i8 226
%1:_(s8) = G_CONSTANT i8 2
%2:_(s8) = G_ROTR %0, %1
...
---
name: CstBig
body: |
bb.1:
; CHECK-LABEL: name: @CstBig
; CHECK-NEXT: %0:_ KnownBits:11111001 SignBits:5
; CHECK-NEXT: %1:_ KnownBits:00000110 SignBits:5
; CHECK-NEXT: %2:_ KnownBits:11100111 SignBits:3
%0:_(s8) = G_CONSTANT i8 249
%1:_(s8) = G_CONSTANT i8 6
%2:_(s8) = G_ROTR %0, %1
...
---
name: CstSext
body: |
bb.1:
; CHECK-LABEL: name: @CstSext
; CHECK-NEXT: %0:_ KnownBits:10000001 SignBits:1
; CHECK-NEXT: %1:_ KnownBits:00000100 SignBits:5
; CHECK-NEXT: %2:_ KnownBits:11111000 SignBits:5
; CHECK-NEXT: %3:_ KnownBits:00000100 SignBits:5
; CHECK-NEXT: %4:_ KnownBits:10001111 SignBits:1
%0:_(s8) = G_CONSTANT i8 129
%1:_(s8) = G_CONSTANT i8 4
%2:_(s8) = G_ASHR %0, %1
%3:_(s8) = G_CONSTANT i8 4
%4:_(s8) = G_ROTR %2, %3
...
---
name: CstSextBig
body: |
bb.1:
; CHECK-LABEL: name: @CstSextBig
; CHECK-NEXT: %0:_ KnownBits:10000001 SignBits:1
; CHECK-NEXT: %1:_ KnownBits:00000100 SignBits:5
; CHECK-NEXT: %2:_ KnownBits:11111000 SignBits:5
; CHECK-NEXT: %3:_ KnownBits:00000110 SignBits:5
; CHECK-NEXT: %4:_ KnownBits:11100011 SignBits:3
%0:_(s8) = G_CONSTANT i8 129
%1:_(s8) = G_CONSTANT i8 4
%2:_(s8) = G_ASHR %0, %1
%3:_(s8) = G_CONSTANT i8 6
%4:_(s8) = G_ROTR %2, %3
...
---
name: ScalarVar
body: |
bb.1:
; CHECK-LABEL: name: @ScalarVar
; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %2:_ KnownBits:???????? SignBits:1
%0:_(s8) = COPY $b0
%1:_(s8) = COPY $b1
%2:_(s8) = G_ROTR %0, %1
...
---
name: ScalarCst
body: |
bb.1:
; CHECK-LABEL: name: @ScalarCst
; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:00000011 SignBits:6
; CHECK-NEXT: %2:_ KnownBits:???????? SignBits:1
%0:_(s8) = COPY $b0
%1:_(s8) = G_CONSTANT i8 3
%2:_(s8) = G_ROTR %0, %1
...
---
name: VectorVar
body: |
bb.1:
; CHECK-LABEL: name: @VectorVar
; CHECK-NEXT: %0:_ KnownBits:???????????????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:???????????????? SignBits:1
; CHECK-NEXT: %2:_ KnownBits:???????????????? SignBits:1
%0:_(<4 x s16>) = COPY $d0
%1:_(<4 x s16>) = COPY $d1
%2:_(<4 x s16>) = G_ROTR %0, %1
...
---
name: VectorSimple
body: |
bb.1:
; CHECK-LABEL: name: @VectorSimple
; CHECK-NEXT: %0:_ KnownBits:0000000000010011 SignBits:11
; CHECK-NEXT: %1:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %2:_ KnownBits:0000000000010011 SignBits:11
; CHECK-NEXT: %3:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %4:_ KnownBits:0110000000000010 SignBits:1
%0:_(s16) = G_CONSTANT i16 19
%1:_(s16) = G_CONSTANT i16 3
%2:_(<4 x s16>) = G_BUILD_VECTOR %0, %0, %0, %0
%3:_(<4 x s16>) = G_BUILD_VECTOR %1, %1, %1, %1
%4:_(<4 x s16>) = G_ROTR %2, %3
...
---
name: VectorCst
body: |
bb.1:
; CHECK-LABEL: name: @VectorCst
; CHECK-NEXT: %0:_ KnownBits:???????????????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %2:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %3:_ KnownBits:???????????????? SignBits:1
%0:_(<4 x s16>) = COPY $d0
%1:_(s16) = G_CONSTANT i16 3
%2:_(<4 x s16>) = G_BUILD_VECTOR %1, %1, %1, %1
%3:_(<4 x s16>) = G_ROTR %0, %2
...
---
name: VectorCst36
body: |
bb.1:
; CHECK-LABEL: name: @VectorCst36
; CHECK-NEXT: %0:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %1:_ KnownBits:0000000000000110 SignBits:13
; CHECK-NEXT: %2:_ KnownBits:0000000000000?1? SignBits:13
; CHECK-NEXT: %3:_ KnownBits:0000000000000?1? SignBits:13
; CHECK-NEXT: %4:_ KnownBits:???????????????? SignBits:1
%0:_(s16) = G_CONSTANT i16 3
%1:_(s16) = G_CONSTANT i16 6
%2:_(<4 x s16>) = G_BUILD_VECTOR %0, %1, %1, %0
%3:_(<4 x s16>) = G_BUILD_VECTOR %0, %1, %1, %0
%4:_(<4 x s16>) = G_ROTR %2, %3
...

---
name: VectorCst3unknown
body: |
bb.1:
; CHECK-LABEL: name: @VectorCst3unknown
; CHECK-NEXT: %0:_ KnownBits:???????????????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:???????????????? SignBits:1
; CHECK-NEXT: %2:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %3:_ KnownBits:???????????????? SignBits:1
; CHECK-NEXT: %4:_ KnownBits:???????????????? SignBits:1
%0:_(<4 x s16>) = COPY $d0
%1:_(s16) = COPY $h0
%2:_(s16) = G_CONSTANT i16 3
%3:_(<4 x s16>) = G_BUILD_VECTOR %1, %2, %2, %1
%4:_(<4 x s16>) = G_ROTR %0, %3
...
---
name: VectorSext
body: |
bb.1:
; CHECK-LABEL: name: @VectorSext
; CHECK-NEXT: %0:_ KnownBits:11101110 SignBits:3
; CHECK-NEXT: %1:_ KnownBits:1111111111101110 SignBits:11
; CHECK-NEXT: %2:_ KnownBits:1111111111101110 SignBits:11
; CHECK-NEXT: %3:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %4:_ KnownBits:0000000000000110 SignBits:13
; CHECK-NEXT: %5:_ KnownBits:0000000000000?1? SignBits:13
; CHECK-NEXT: %6:_ KnownBits:???????????????? SignBits:1
%0:_(s8) = G_CONSTANT i8 238
%1:_(s16) = G_SEXT %0(s8)
%2:_(<4 x s16>) = G_BUILD_VECTOR %1, %1, %1, %1
%3:_(s16) = G_CONSTANT i16 3
%4:_(s16) = G_CONSTANT i16 6
%5:_(<4 x s16>) = G_BUILD_VECTOR %3, %4, %4, %3
%6:_(<4 x s16>) = G_ROTR %2, %5
...
---
name: VectorSextBig
body: |
bb.1:
; CHECK-LABEL: name: @VectorSextBig
; CHECK-NEXT: %0:_ KnownBits:11101110 SignBits:3
; CHECK-NEXT: %1:_ KnownBits:1111111111101110 SignBits:11
; CHECK-NEXT: %2:_ KnownBits:1111111111101110 SignBits:11
; CHECK-NEXT: %3:_ KnownBits:0000000000001000 SignBits:12
; CHECK-NEXT: %4:_ KnownBits:0000000000001001 SignBits:12
; CHECK-NEXT: %5:_ KnownBits:000000000000100? SignBits:12
; CHECK-NEXT: %6:_ KnownBits:???????????????? SignBits:1
%0:_(s8) = G_CONSTANT i8 238
%1:_(s16) = G_SEXT %0(s8)
%2:_(<4 x s16>) = G_BUILD_VECTOR %1, %1, %1, %1
%3:_(s16) = G_CONSTANT i16 8
%4:_(s16) = G_CONSTANT i16 9
%5:_(<4 x s16>) = G_BUILD_VECTOR %3, %4, %4, %3
%6:_(<4 x s16>) = G_ROTR %2, %5
...
---
name: ROTRless
body: |
bb.1:
; CHECK-LABEL: name: @ROTRless
; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:???????????????? SignBits:9
; CHECK-NEXT: %2:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %3:_ KnownBits:???????????????? SignBits:1
%0:_(s8) = COPY $b0
%1:_(s16) = G_SEXT %0(s8)
%2:_(s16) = G_CONSTANT i16 3
%3:_(s16) = G_ROTR %1, %2
...
---
name: ROTReq
body: |
bb.1:
; CHECK-LABEL: name: @ROTReq
; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:???????????????? SignBits:9
; CHECK-NEXT: %2:_ KnownBits:0000000000001000 SignBits:12
; CHECK-NEXT: %3:_ KnownBits:???????????????? SignBits:1
%0:_(s8) = COPY $b0
%1:_(s16) = G_SEXT %0(s8)
%2:_(s16) = G_CONSTANT i16 8
%3:_(s16) = G_ROTR %1, %2
...
---
name: ROTRmore
body: |
bb.1:
; CHECK-LABEL: name: @ROTRmore
; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:???????????????? SignBits:9
; CHECK-NEXT: %2:_ KnownBits:0000000000001101 SignBits:12
; CHECK-NEXT: %3:_ KnownBits:???????????????? SignBits:1
%0:_(s8) = COPY $b0
%1:_(s16) = G_SEXT %0(s8)
%2:_(s16) = G_CONSTANT i16 13
%3:_(s16) = G_ROTR %1, %2
...
---
name: SignBitsThroughZext
body: |
bb.1:
; CHECK-LABEL: name: @SignBitsThroughZext
; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
; CHECK-NEXT: %1:_ KnownBits:0000000000000011 SignBits:14
; CHECK-NEXT: %2:_ KnownBits:???????? SignBits:4
; CHECK-NEXT: %3:_ KnownBits:00000000???????? SignBits:8
; CHECK-NEXT: %4:_ KnownBits:0000000000001000 SignBits:12
; CHECK-NEXT: %5:_ KnownBits:????????00000000 SignBits:1
%0:_(s8) = COPY $b0
%1:_(s16) = G_CONSTANT i16 3
%2:_(s8) = G_ASHR %0, %1
%3:_(s16) = G_ZEXT %2
%4:_(s16) = G_CONSTANT i16 8
%5:_(s16) = G_ROTR %3, %4
...
---
name: ROTRCanonicalize
body: |
bb.1:
; CHECK-LABEL: name: @ROTRCanonicalize
; CHECK-NEXT: %0:_ KnownBits:11100000 SignBits:3
; CHECK-NEXT: %1:_ KnownBits:00000010 SignBits:6
; CHECK-NEXT: %2:_ KnownBits:10000011 SignBits:1
%0:_(s8) = G_CONSTANT i8 224
%1:_(s8) = G_CONSTANT i8 2
%2:_(s8) = G_ROTL %0, %1
...