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Re: Optimizer Questions



  In message <13712.56819.874875.486735@polyxena>you write:
  > 
  > [1] The flag -fmove-all-movables does not seem to have any effect:
  > 
  >     gcc -fmove-all-movables -S T.c
  >     gcc -S T.c
  > 
  >     produce the same assembler file (no moving in either case), as do
  > 
  >     gcc -O2 -fno-move-all-movables -S T.c
  >     gcc -O2 -S T.c
Probably because there are no additional moveables in your code.

In larger loops, the compiler's heuristics may indicate that a particular
movable isn't profitable to move.  This flag tells the compiler to move
it anyway.


  > [2] Code moving produces an empty loop, which is not removed.
  >     (See below for the output with -O2)
This is a "feature" and the documented behavior of the compiler.  That
may change (there's a recent long thread on this topic that I need to
review).

jeff


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