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Fixed BTC flag calculation #79

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Merged
ltfish merged 1 commit into from
Feb 1, 2026
Merged

Fixed BTC flag calculation #79

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34 changes: 20 additions & 14 deletions priv/guest_amd64_toIR.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8378,20 +8378,26 @@ ULong dis_bt_G_E ( const VexAbiInfo* vbi,
}

/* Side effect done; now get selected bit into Carry flag */
/* Flags: C=selected bit, O,S,Z,A,P undefined, so are set to zero. */
stmt( IRStmt_Put( OFFB_CC_OP, mkU64(AMD64G_CC_OP_COPY) ));
stmt( IRStmt_Put( OFFB_CC_DEP2, mkU64(0) ));
stmt( IRStmt_Put(
OFFB_CC_DEP1,
binop(Iop_And64,
binop(Iop_Shr64,
unop(Iop_8Uto64, mkexpr(t_fetched)),
mkexpr(t_bitno2)),
mkU64(1)))
);
/* Set NDEP even though it isn't used. This makes redundant-PUT
elimination of previous stores to this field work better. */
stmt( IRStmt_Put( OFFB_CC_NDEP, mkU64(0) ));
/* Flags: C=selected bit, Z=unaffected, O,S,A,P undefined */
IRTemp old_cc = newTemp(Ity_I64);
assign(old_cc, IRExpr_Get(OFFB_CC_DEP1, Ity_I64));

IRTemp new_cf = newTemp(Ity_I64);
assign(new_cf, binop(Iop_And64,
binop(Iop_Shr64, unop(Iop_8Uto64, mkexpr(t_fetched)),
mkexpr(t_bitno2)),
mkU64(1)));

/* Replace CF but reserve the old flags (for ZF) */
IRTemp merged = newTemp(Ity_I64);
assign(merged,
binop(Iop_Or64,
binop(Iop_And64, mkexpr(old_cc), mkU64(~AMD64G_CC_MASK_C)),
mkexpr(new_cf)));

stmt(IRStmt_Put(OFFB_CC_OP, mkU64(AMD64G_CC_OP_COPY)));
stmt(IRStmt_Put(OFFB_CC_DEP1, mkexpr(merged)));
stmt(IRStmt_Put(OFFB_CC_DEP2, mkU64(0)));

/* Move reg operand from stack back to reg */
if (epartIsReg(modrm)) {
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