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rtl.texi (CALL_INSN_FUNCTION_USAGE): Note that (and when) it may contain MEMs. 

* rtl.texi (CALL_INSN_FUNCTION_USAGE): Note that (and when) it may
contain MEMs.  Remove useless distinction about clobbering
registers.

From-SVN: r42060
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Alexandre Oliva 2001-05-14 05:11:38 +00:00 committed by Alexandre Oliva
parent e44713f730
commit c78df6e155
2 changed files with 25 additions and 6 deletions
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6
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@ -1,3 +1,9 @@
2001-05-14 Alexandre Oliva <aoliva@redhat.com>
* rtl.texi (CALL_INSN_FUNCTION_USAGE): Note that (and when) it may
contain MEMs. Remove useless distinction about clobbering
registers.
2001-05-13 Geoff Keating <geoffk@redhat.com>
* config/rs6000/rs6000.h (EXCEPTION_SECTION): Move to...

25
gcc/rtl.texi
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@ -2530,12 +2530,25 @@ unpredictably.
accessed in the same way and in addition contain a field
@code{CALL_INSN_FUNCTION_USAGE}, which contains a list (chain of
@code{expr_list} expressions) containing @code{use} and @code{clobber}
expressions that denote hard registers used or clobbered by the called
function. A register specified in a @code{clobber} in this list is
modified @emph{after} the execution of the @code{call_insn}, while a
register in a @code{clobber} in the body of the @code{call_insn} is
clobbered before the insn completes execution. @code{clobber}
expressions in this list augment registers specified in
expressions that denote hard registers and @code{MEM}s used or
clobbered by the called function.
A @code{MEM} generally points to a stack slots in which arguments passed
to the libcall by reference (@pxref{Register Arguments,
FUNCTION_ARG_PASS_BY_REFERENCE}) are stored. If the argument is
caller-copied (@pxref{Register Arguments, FUNCTION_ARG_CALLEE_COPIES}),
the stack slot will be mentioned in @code{CLOBBER} and @code{USE}
entries; if it's callee-copied, only a @code{USE} will appear, and the
@code{MEM} may point to addresses that are not stack slots. These
@code{MEM}s are used only in libcalls, because, unlike regular function
calls, @code{CONST_CALL}s (which libcalls generally are, @pxref{Flags,
CONST_CALL_P}) aren't assumed to read and write all memory, so flow
would consider the stores dead and remove them. Note that, since a
libcall must never return values in memory (@pxref{Aggregate Return,
RETURN_IN_MEMORY}), there will never be a @code{CLOBBER} for a memory
address holding a return value.
@code{CLOBBER}ed registers in this list augment registers specified in
@code{CALL_USED_REGISTERS} (@pxref{Register Basics}).
@findex code_label