Fix generation of immediates for and/or/xor. #1553
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We were incorrectly sign extending immediates in these cases, which was particularly obvious in the `i1` case where things like `xor %0, 1i1` would become (in x64) `xor r11d, 0xffffffff`. This commit splits apart zero and sign extension cases more carefully so that `xor r11d, 0x01` is generated.
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So this is an optimisation, right? |
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No -- it's a fix! |
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We spoke about this offline and, although the old generated code harder for a human to read, it appears to be correct. The new generated code is also correct, so I'm merging this on the grounds that it makes the generated code easier for a human to read. That it fixes something suggests that some other operation is failing to zero off undefined bits before doing its computation, but @ltratt says he's cooking something up to make it harder for that to happen in the future. |
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We were incorrectly sign extending immediates in these cases, which was particularly obvious in the
i1case where things likexor %0, 1i1would become (in x64)xor r11d, 0xffffffff. This commit splits apart zero and sign extension cases more carefully so thatxor r11d, 0x01is generated.