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xermicus
40e97d11eb
Existing test coverage didn't catch a signed remainder overflow semantics edge case behavior where at least one the operators is being constant folded by LLVM instead of solc. This PR fixes the SREM translation bug and adds missing test coverage for division ops with constants. Closes #524 --------- Signed-off-by: xermicus <cyrill@parity.io>
28 lines
1.1 KiB
Plaintext
28 lines
1.1 KiB
Plaintext
/// Dedicated fixture exercising `sdiv(INT_MIN, -1)` — the signed-overflow UB
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/// case for division, sibling to the `smod` bug in paritytech/revive#524.
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///
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/// LLVM `sdiv` is UB when the dividend is `INT_MIN` and the divisor is `-1`
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/// (the mathematical result `-INT_MIN` overflows). EVM SDIV defines this as
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/// `INT_MIN`. revive's `__revive_signed_division` runtime function is supposed
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/// to guard this; the issue says sdiv is already guarded but having a test
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/// here protects against regressions and surfaces any future divergence.
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///
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/// See `SmodIntMinNegOneBug.yul` for the rationale behind the Yul expression
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/// operands and the lack of a `switch` dispatcher.
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object "SdivIntMinNegOneBug" {
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code {
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let size := datasize("SdivIntMinNegOneBug_deployed")
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codecopy(0, dataoffset("SdivIntMinNegOneBug_deployed"), size)
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return(0, size)
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}
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object "SdivIntMinNegOneBug_deployed" {
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code {
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let tag := calldataload(0)
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let int_min := shl(255, 1)
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let neg_one := sar(58, shl(58, sub(0, 1)))
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mstore(0, xor(sdiv(int_min, neg_one), tag))
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return(0, 32)
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}
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}
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}
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