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ZJIT: Split shift with immediate operand #13914

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Merged
merged 1 commit into from
Jul 16, 2025
Merged

ZJIT: Split shift with immediate operand #13914

merged 1 commit into from
Jul 16, 2025

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tekknolagi
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@tekknolagi tekknolagi commented Jul 16, 2025 •
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@matzbot matzbot requested a review from a team July 16, 2025 18:50
tekknolagi
tekknolagi commented Jul 16, 2025
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@tekknolagi tekknolagi force-pushed the mb-shift-imm branch 2 times, most recently from 6a97041 to e365f99 Compare July 16, 2025 18:54
@tekknolagi tekknolagi enabled auto-merge (squash) July 16, 2025 18:54
st0012
st0012 reviewed Jul 16, 2025
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test/ruby/test_zjit.rb
def test(n) = C * n
test(4)
test(4)
test(4)
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How does the script generate the URShift instruction and is it possible to see it in dumped HIR output?

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No, it's only in LIR; it's a shift for untagging

Optimized HIR:
fn test@testshift.rb:4:
bb0(v0:BasicObject, v1:BasicObject):
  PatchPoint SingleRactorMode
  PatchPoint StableConstantNames(0x600001b86020, RP2A03_CC)
  v10:Fixnum[12] = Const Value(12)
  PatchPoint BOPRedefined(INTEGER_REDEFINED_OP_FLAG, BOP_MULT)
  v13:Fixnum = GuardType v1, Fixnum
  v14:Fixnum = FixnumMult v10, v13
  Return v14

LIR:
fn test:
Assembler
    000 Label() target=Label(Label(0)) -> None
    001 FrameSetup() -> None
    002 LiveReg(A64Reg { num_bits: 64, reg_no: 0 }) -> VReg(0)
    003 LiveReg(A64Reg { num_bits: 64, reg_no: 1 }) -> VReg(1)
    004 PatchPoint(VReg(1)) target=SideExit { pc: 0x600000cbae00, stack: [], locals: [VReg(1)], c_stack_bytes: 0, reason: PatchPoint(SingleRactorMode), label: Some(Label(1)) } -> None
    005 PosMarker() -> None
    006 PatchPoint(VReg(1)) target=SideExit { pc: 0x600000cbae00, stack: [], locals: [VReg(1)], c_stack_bytes: 0, reason: PatchPoint(StableConstantNames { idlist: 0x600001b86020 }), label: Some(Label(2)) } -> None
    007 PosMarker() -> None
    008 PatchPoint(Value(VALUE(25)), VReg(1), VReg(1)) target=SideExit { pc: 0x600000cbae20, stack: [Value(VALUE(25)), VReg(1)], locals: [VReg(1)], c_stack_bytes: 0, reason: PatchPoint(BOPRedefined { klass: 1, bop: 2 }), label: Some(Label(3)) } -> None
    009 PosMarker() -> None
    010 Test(VReg(1), 1_u64) -> None
    011 Jz(Value(VALUE(25)), VReg(1), VReg(1)) target=SideExit { pc: 0x600000cbae20, stack: [Value(VALUE(25)), VReg(1)], locals: [VReg(1)], c_stack_bytes: 0, reason: GuardType(Type { bits: 4194304, spec: Any }), label: None } -> None
    012 RShift(Value(VALUE(25)), 1_u64) -> VReg(2)
    013 Sub(VReg(1), 1_u64) -> VReg(3)
    014 Mul(VReg(2), VReg(3)) -> VReg(4)
    015 JoMul(Value(VALUE(25)), VReg(1), VReg(1)) target=SideExit { pc: 0x600000cbae20, stack: [Value(VALUE(25)), VReg(1)], locals: [VReg(1)], c_stack_bytes: 0, reason: FixnumMultOverflow, label: None } -> None
    016 Add(VReg(4), 1_u64) -> VReg(5)
    017 Add(A64Reg { num_bits: 64, reg_no: 19 }, 38_u64) -> VReg(6)
    018 Mov(A64Reg { num_bits: 64, reg_no: 19 }, VReg(6)) -> None
    019 Mov(Mem64[Reg(20) + 16], A64Reg { num_bits: 64, reg_no: 19 }) -> None
    020 FrameTeardown() -> None
    021 CRet(VReg(5)) -> None
    022 PadPatchPoint() -> None

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Ah sorry I'm blind on the file name 🤦

@XrXr
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XrXr commented Jul 16, 2025 

 TestZJIT#test_fixnum_mul [/home/runner/work/ruby/ruby/src/test/ruby/test_zjit.rb:386]:

  thread '<unnamed>' panicked at zjit/src/asm/x86_64/mod.rs:1252:5:
  assertion failed: matches!(opnd0, X86Opnd::Reg(_) | X86Opnd::Mem(_))

Will need a fix on x86 as well 😢

@tekknolagi tekknolagi merged commit 900eb04 into ruby:master Jul 16, 2025
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@tekknolagi tekknolagi deleted the mb-shift-imm branch July 16, 2025 19:50
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ZJIT: Running optcarrot (on ARM64) causes assembler panic
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