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Fix concrete zero-modulus ADDMOD and MULMOD #588

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Fix concrete zero-modulus ADDMOD and MULMOD #588

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4 changes: 4 additions & 0 deletions src/halmos/bitvec.py
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Original file line number Diff line number Diff line change
Expand Up @@ -734,6 +734,8 @@ def addmod(
assert size == modulus.size

if self.is_concrete and other.is_concrete and modulus.is_concrete:
if modulus.value == 0:
return modulus
return HalmosBitVec((self.value + other.value) % modulus.value, size=size)

# to avoid add overflow; and to be a multiple of 8-bit
Expand Down Expand Up @@ -762,6 +764,8 @@ def mulmod(
assert size == modulus.size

if self.is_concrete and other.is_concrete and modulus.is_concrete:
if modulus.value == 0:
return modulus
return HalmosBitVec((self.value * other.value) % modulus.value, size=size)

# to avoid mul overflow
Expand Down
2 changes: 2 additions & 0 deletions tests/test_sevm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,7 @@ def byte_of(i, x):
(o(EVM.SMOD), [x, BV(0)], BV(0)),
(o(EVM.SMOD), [x, BV(1)], BV(0)),
(o(EVM.ADDMOD), [BV(4), BV(1), BV(3)], BV(2)),
(o(EVM.ADDMOD), [BV(4), BV(1), BV(0)], BV(0)),
(o(EVM.ADDMOD), [x, y, BV(0)], BV(0)),
(o(EVM.ADDMOD), [x, y, BV(1)], BV(0)),
(
Expand Down Expand Up @@ -229,6 +230,7 @@ def byte_of(i, x):
BV(1),
),
(o(EVM.MULMOD), [BV(5), BV(1), BV(3)], BV(2)),
(o(EVM.MULMOD), [BV(5), BV(1), BV(0)], BV(0)),
(o(EVM.MULMOD), [x, y, BV(0)], BV(0)),
(o(EVM.MULMOD), [x, y, BV(1)], BV(0)),
(
Expand Down