[Codegen] Potential stack corruption?

[bshastry]

contract C {
  bytes30 s = 0;
  function f(int i) public {
    payable(this).transfer(0);
  }
  receive() external payable {
    s;
    bytes30 l;
    assert(l == s);
  }
}
// ----
// f(int256): 0 ->

reverts without optimization only. With optimization it passes

Repro

$ cp test.sol test/libsolidity/semanticTests
$ isoltest -t semanticTests/test

[bshastry]

It looks like an assertion failure but a panic code (https://docs.soliditylang.org/en/latest/control-structures.html#panic-via-assert-and-error-via-require) is not emitted. transfer may be reverting and not propagating the panic due to failed assertion.

[bshastry]

Closing because @chriseth strongly feels this has to do with gas throttling of the transfer call, and the storage read in receive being too expensive for unoptimized code.