Commits on Sep 11, 2023

1. x64: Remove recursion in to_amode helper …

   This commit removes the recursion present in the x64 backend's
   `to_amode` and `to_amode_add` helpers. The recursion is currently
   unbounded and controlled by user input meaning it's not too hard to
   craft user input which triggers stack overflow in the host. By removing
   recursion there's no need to worry about this since the stack depth will
   never be hit.
   
   The main concern with removing recursion is that code quality may not be
   quite as good any more. The purpose of the recursion here is to "hunt
   for constants" and update the immediate `Offset32`, and now without
   recursion only at most one constant is found and folded instead of an
   arbitrary number of constants as before. This should continue to produce
   the same code as before so long as optimizations are enabled, but
   without optimizations this will produce worse code than before.
   
   Note with a hypothetical mid-end optimization that does this constant
   folding for us the rules here could be further simplified to purely
   consider the shape of the input `Value` to amode computation without
   considering constants at all.

   

   alexcrichton committed Sep 11, 2023
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