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rtl.def (POST_MODIFY, PRE_MODIFY): New generalized operators for addressing modes with side effects.

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* rtl.def (POST_MODIFY, PRE_MODIFY): New generalized operators for
  	addressing modes with side effects.  These are currently
  	placeholders for the C4x target.

From-SVN: r23228
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Michael Hayes 1998-10-22 16:11:16 +00:00 committed by Michael Hayes
parent f76707606e
commit b18cfc2861
3 changed files with 47 additions and 1 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
Fri Oct 23 11:11:56 1998 Michael Hayes <m.hayes@elec.canterbury.ac.nz>
* rtl.def (POST_MODIFY, PRE_MODIFY): New generalized operators for
addressing modes with side effects. These are currently
placeholders for the C4x target.
Thu Oct 22 16:46:35 1998 Bernd Schmidt <crux@pool.informatik.rwth-aachen.de>
* loop.c (express_from): Make sure that when generating a PLUS of

8
gcc/rtl.def
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@ -723,6 +723,14 @@ DEF_RTL_EXPR(PRE_INC, "pre_inc", "e", 'x')
DEF_RTL_EXPR(POST_DEC, "post_dec", "e", 'x')
DEF_RTL_EXPR(POST_INC, "post_inc", "e", 'x')
/* These binary operations are used to represent generic address
side-effects in memory addresses, except for simple incrementation
or decrementation which use the above operations. They are
created automatically by the life_analysis pass in flow.c.
(Note that these operators are currently placeholders.) */
DEF_RTL_EXPR(PRE_MODIFY, "pre_modify", "ee", 'x')
DEF_RTL_EXPR(POST_MODIFY, "post_modify", "ee", 'x')
/* Comparison operations. The ordered comparisons exist in two
flavors, signed and unsigned. */
DEF_RTL_EXPR(NE, "ne", "ee", '<')

34
gcc/rtl.texi
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@ -2036,7 +2036,7 @@ and of @var{min} and @var{max} to @var{base}. See rtl.def for details.@refill
@cindex RTL predecrement
@cindex RTL postdecrement
Four special side-effect expression codes appear as memory addresses.
Six special side-effect expression codes appear as memory addresses.
@table @code
@findex pre_dec
@ -2071,6 +2071,38 @@ being decremented.
@findex post_inc
@item (post_inc:@var{m} @var{x})
Similar, but specifies incrementing @var{x} instead of decrementing it.
@findex post_modify
@item (post_modify:@var{m} @var{x} @var{y})
Represents the side effect of setting @var{x} to @var{y} and
represents @var{x} before @var{x} is modified. @var{x} must be a
@code{reg} or @code{mem}, but most machines allow only a @code{reg}.
@var{m} must be the machine mode for pointers on the machine in use.
The amount @var{x} is decremented by is the length in bytes of the
machine mode of the containing memory reference of which this expression
serves as the address. Note that this is not currently implemented.
The expression @var{y} must be one of three forms:
@table @code
@code{(plus:@var{m} @var{x} @var{z})},
@code{(minus:@var{m} @var{x} @var{z})}, or
@code{(plus:@var{m} @var{x} @var{i})},
@end table
where @var{z} is an index register and @var{i} is a constant.
Here is an example of its use:@refill
@example
(mem:SF (post_modify:SI (reg:SI 42) (plus (reg:SI 42) (reg:SI 48))))
@end example
This says to modify pseudo register 42 by adding the contents of pseudo
register 48 to it, after the use of what ever 42 points to.
@findex post_modify
@item (pre_modify:@var{m} @var{x} @var{expr})
Similar except side effects happen before the use.
@end table
These embedded side effect expressions must be used with care. Instruction