Collaboration diagram for loop_data:

Data Fields
class loop *	outermost_exit

bool	has_call

int	max_reg_pressure [N_REG_CLASSES]

bitmap_head	regs_ref

bitmap_head	regs_live

Detailed Description

RTL-level loop invariant motion.
   Copyright (C) 2004-2024 Free Software Foundation, Inc.

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This implements the loop invariant motion pass.  It is very simple
(no calls, no loads/stores, etc.).  This should be sufficient to cleanup
things like address arithmetics -- other more complicated invariants should
be eliminated on GIMPLE either in tree-ssa-loop-im.cc or in tree-ssa-pre.cc.

We proceed loop by loop -- it is simpler than trying to handle things
globally and should not lose much.  First we inspect all sets inside loop
and create a dependency graph on insns (saying "to move this insn, you must
also move the following insns").

We then need to determine what to move.  We estimate the number of registers
used and move as many invariants as possible while we still have enough free
registers.  We prefer the expensive invariants.

Then we move the selected invariants out of the loop, creating a new
temporaries for them if necessary.