Use sign-extension to save instructions

b9832e268cfc26dafad1f1c30f6b7673b8c1c6c2a89db0ef837be08af3fc31d6
Alexis Sellier committed ago 1 parent 68bd0f27
lib/std/arch/rv64/isel.rad +17 -8
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            selectShift(s, rd, rs1, b, ShiftOp::Sra, typ, super::SCRATCH2),
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        case il::BinOp::Ushr =>
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            selectShift(s, rd, rs1, b, ShiftOp::Srl, typ, super::SCRATCH2),
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        case il::BinOp::Eq => {
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            let rs2 = resolveVal(s, super::SCRATCH2, b);
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            // Canonicalize both operands to the declared width
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            // so high-bit junk doesn't affect the result.
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            emitZext(s.e, rs1, rs1, typ);
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            emitZext(s.e, rs2, rs2, typ);
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            // Canonicalize both operands to the declared width.
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            // For W32 EQ, sign-extension suffices instead of
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            // zero-extension since both sides get same canonical form.
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            if typ == il::Type::W32 {
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                emitSext(s.e, rs1, rs1, typ);
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                emitSext(s.e, rs2, rs2, typ);
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            } else {
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                emitZext(s.e, rs1, rs1, typ);
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                emitZext(s.e, rs2, rs2, typ);
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            }
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            emit::emit(s.e, encode::xor(rd, rs1, rs2));
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            emit::emit(s.e, encode::sltiu(rd, rd, 1));
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        }
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        case il::BinOp::Ne => {
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            let rs2 = resolveVal(s, super::SCRATCH2, b);
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            // Canonicalize both operands to the declared width
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            // so high-bit junk doesn't affect the result.
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            emitZext(s.e, rs1, rs1, typ);
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            emitZext(s.e, rs2, rs2, typ);
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            if typ == il::Type::W32 {
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                emitSext(s.e, rs1, rs1, typ);
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                emitSext(s.e, rs2, rs2, typ);
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            } else {
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                emitZext(s.e, rs1, rs1, typ);
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                emitZext(s.e, rs2, rs2, typ);
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            }
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            emit::emit(s.e, encode::xor(rd, rs1, rs2));
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            emit::emit(s.e, encode::sltu(rd, super::ZERO, rd));
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        }
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        case il::BinOp::Slt =>
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            selectCmp(s, rd, rs1, b, CmpOp::Slt, super::SCRATCH2),