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loop.c (scan_loop): Be more selective about what invariants are moved out of a loop. 

* loop.c (scan_loop): Be more selective about what invariants are
        moved out of a loop.

From-SVN: r23178
This commit is contained in:
Jeffrey A Law 1998-10-19 12:20:32 +00:00 committed by Jeff Law
parent 38bf4c6fcd
commit e1f7435e41
2 changed files with 10 additions and 14 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Mon Oct 19 11:40:56 1998 Jeffrey A Law (law@cygnus.com)
* loop.c (scan_loop): Be more selective about what invariants are
moved out of a loop.
Mon Oct 19 10:46:58 PDT 1998 Jeff Law (law@cygnus.com)
* version.c: Bump for snapshot.

19
gcc/loop.c
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@ -837,13 +837,7 @@ scan_loop (loop_start, end, unroll_p, bct_p)
We don't know its life-span, so we can't compute the benefit. */
if (REGNO (SET_DEST (set)) >= max_reg_before_loop)
;
else if (/* The set is a user-variable or it is used in
the exit test (this can cause the variable to be
used before it is set just like a
user-variable)... */
(REG_USERVAR_P (SET_DEST (set))
|| REG_LOOP_TEST_P (SET_DEST (set)))
/* And the set is not guaranteed to be executed one
else if (/* The set is not guaranteed to be executed one
the loop starts, or the value before the set is
needed before the set occurs... */
&& (maybe_never
@ -854,14 +848,11 @@ scan_loop (loop_start, end, unroll_p, bct_p)
something after this point in the loop might
depend on its value before the set). */
&& !reg_in_basic_block_p (p, SET_DEST (set)))
/* It is unsafe to move the set. The fact that these
three conditions are considered in conjunction means
that we are assuming various conditions, such as:
/* It is unsafe to move the set.
o It's OK to move a set of a variable which was not
created by the user and is not used in an exit test
even if that point in the set would not be reached
during execution of the loop. */
This code used to consider it OK to move a set of a variable
which was not created by the user and not used in an exit test.
That behavior is incorrect and was removed. */
;
else if ((tem = invariant_p (src))
&& (dependencies == 0