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authorBjörn Gustavsson <[email protected]>2015-10-05 06:43:12 +0200
committerBjörn Gustavsson <[email protected]>2015-10-05 12:47:55 +0200
commit76bb9f0e9a0b36ea7c9720c2bf90f6b52a4eabf8 (patch)
tree47e29acaeafb5025531d8736ffb7ded30cf678a3 /bootstrap
parent7dd616c1832c54370be7f796a4b6578a8d9aedd9 (diff)
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beam_reorder: Eliminate compiler crash
c288ab87 added beam_reorder to move get_tuple_element instructions. Compiling code such as the following would crash the compiler: alloc(_U1, _U2, R) -> V = R#alloc.version, Res = id(V), _ = id(0), Res. The crash would occur because the following two instructions: {get_tuple_element,{x,2},1,{x,1}}. {allocate_zero,1,2}. were swapped and rewritten to: {allocate_zero,1,1}. {get_tuple_element,{x,2},1,{x,1}}. That transformation is not safe because the allocate_zero instruction would kill {x,2}, which is the register that is holding the reference to the tuple. Only do the transformation when the tuple reference is in an x register with a lower number than the destination register.
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