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fix(evm): pin MLOAD results to prevent stale memory reads in multipass JIT #364

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fix(evm): pin MLOAD results to prevent stale memory reads in multipass JIT #364

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fix(evm): pin MLOAD results to prevent stale memory reads in multipas…
starwarfan Feb 26, 2026
4b668d6
fix: Update src/compiler/evm_frontend/evm_mir_compiler.cpp
starwarfan Feb 28, 2026
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12 changes: 12 additions & 0 deletions src/compiler/evm_frontend/evm_mir_compiler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2693,6 +2693,18 @@ EVMMirBuilder::handleMLoad(Operand AddrComponents) {

Operand Bytes32Op(MemPtr, EVMType::BYTES32);
Operand Result = convertBytes32ToU256Operand(Bytes32Op);

// Pin loaded values into local variables so the backend cannot reschedule
// the memory reads past later function calls (e.g. CODECOPY / MSTORE) that
// may modify the same memory region. Without this, an MLOAD result that
// stays on the EVM stack across a memory-writing opcode could observe the
// *new* contents instead of the value at the time of the MLOAD.
U256Inst Parts = extractU256Operand(Result);
for (int I = 0; I < static_cast<int>(EVM_ELEMENTS_COUNT); ++I) {
Parts[I] = protectUnsafeValue(Parts[I], I64Type);
}
Result = Operand(Parts, EVMType::UINT256);

#ifdef ZEN_ENABLE_EVM_GAS_REGISTER
reloadGasFromMemory();
#endif
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