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Re: Set RTX_UNCHANGING is readonly_field_p when clearing
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: mark at codesourcery dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 21 Apr 03 18:44:33 EDT
- Subject: Re: Set RTX_UNCHANGING is readonly_field_p when clearing
Just put the rule in the manual.
OK:
*** doc/rtl.texi 21 Apr 2003 22:13:01 -0000 1.52
--- doc/rtl.texi 21 Apr 2003 22:38:54 -0000
***************
*** 726,733 ****
Nonzero in a @code{reg}, @code{mem}, or @code{concat} if the register or
memory is set at most once, anywhere. This does not mean that it is
! function invariant. This flag is used to determine whether two
! references conflict. See @code{tree_dependence} in @file{alias.c} for
! more details. Stored in the @code{unchanging} field and printed as
! @samp{/u}.
@findex SCHED_GROUP_P
--- 726,744 ----
Nonzero in a @code{reg}, @code{mem}, or @code{concat} if the register or
memory is set at most once, anywhere. This does not mean that it is
! function invariant.
!
! GCC uses this flag to determine whether two references conflict. As
! implemented by @code{true_dependence} in @file{alias.c} for memory
! references, unchanging memory can't conflict with non-unchanging memory;
! a non-unchanging read can conflict with a non-unchanging write; an
! unchanging read can conflict with an unchanging write (since there may
! be a single store to this address to initialize it); and an unchanging
! store can conflict with a non-unchanging read. This means we must make
! conservative assumptions when chosing the value of this flag for a
! memory reference to an object containing both unchanging and
! non-unchanging fields: we must set the flag when writing to the object
! and clear it when reading from the object.
!
! Stored in the @code{unchanging} field and printed as @samp{/u}.
@findex SCHED_GROUP_P