GCC modified for the FreeChainXenon project
323d010fa5
Use INT_MIN rather than -1 in `comparison_qty' where a comparison is not with a register, because the value of -1 is actually a valid reference to register 0 in the case where it has not been assigned a quantity. Using -1 makes `REG_QTY (REGNO (folded_arg1)) == ent->comparison_qty' comparison in `fold_rtx' to incorrectly trigger in rare circumstances and return true for a memory reference, making CSE consider a comparison operation to evaluate to a constant expression and consequently make the resulting code incorrectly execute or fail to execute conditional blocks. This has caused a miscompilation of rwlock.c from LinuxThreads for the `alpha-linux-gnu' target, where `rwlock->__rw_writer != thread_self ()' expression (where `thread_self' returns the thread pointer via a PALcode call) has been decided to be always true (with `ent->comparison_qty' using -1 for a reference to to `rwlock->__rw_writer', while register 0 holding the thread pointer retrieved by `thread_self') and code for the false case has been optimized away where it mustn't have, causing program lockups. The issue has been observed as a regression from commit |
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