* emit-rtl.c (start_sequence): Expand comments.
(start_sequence_for_rtl_expr): Likewise.
(push_to_sequence): Likewise.
(end_sequence): Likewise.
* expr.c (inhibit_defer_pop): Likewise.
* expr.h (inhibit_defer_pop): Likewise.
(NO_DEFER_POP): Likewise.
(OK_DEFER_POP): Likewise.
From-SVN: r26704
+Thu Apr 29 23:02:22 1999 Mark Mitchell <mark@codesourcery.com>
+
+ * emit-rtl.c (start_sequence): Expand comments.
+ (start_sequence_for_rtl_expr): Likewise.
+ (push_to_sequence): Likewise.
+ (end_sequence): Likewise.
+ * expr.c (inhibit_defer_pop): Likewise.
+ * expr.h (inhibit_defer_pop): Likewise.
+ (NO_DEFER_POP): Likewise.
+ (OK_DEFER_POP): Likewise.
+
Thu Apr 29 22:13:46 1999 Robert Lipe <robertlipe@usa.net>
* configure.in (i?86-UnixWare7*-sysv): Set thread_file to 'posix'
abort ();
}
\f
-/* Begin emitting insns to a sequence which can be packaged in an RTL_EXPR. */
+/* Begin emitting insns to a sequence which can be packaged in an
+ RTL_EXPR. If this sequence will contain something that might cause
+ the compiler to pop arguments to function calls (because those
+ pops have previously been deferred; see INHIBIT_DEFER_POP for more
+ details), use do_pending_stack_adjust before calling this function.
+ That will ensure that the deferred pops are not accidentally
+ emitted in the middel of this sequence. */
void
start_sequence ()
last_insn = 0;
}
-/* Similarly, but indicate that this sequence will be placed in
- T, an RTL_EXPR. */
+/* Similarly, but indicate that this sequence will be placed in T, an
+ RTL_EXPR. See the documentation for start_sequence for more
+ information about how to use this function. */
void
start_sequence_for_rtl_expr (t)
sequence_rtl_expr = t;
}
-/* Set up the insn chain starting with FIRST
- as the current sequence, saving the previously current one. */
+/* Set up the insn chain starting with FIRST as the current sequence,
+ saving the previously current one. See the documentation for
+ start_sequence for more information about how to use this function. */
void
push_to_sequence (first)
/* After emitting to a sequence, restore previous saved state.
- To get the contents of the sequence just made,
- you must call `gen_sequence' *before* calling here. */
+ To get the contents of the sequence just made, you must call
+ `gen_sequence' *before* calling here.
+
+ If the compiler might have deferred popping arguments while
+ generating this sequence, and this sequence will not be immediately
+ inserted into the instruction stream, use do_pending_stack_adjust
+ before calling gen_sequence. That will ensure that the deferred
+ pops are inserted into this sequence, and not into some random
+ location in the instruction stream. See INHIBIT_DEFER_POP for more
+ information about deferred popping of arguments. */
void
end_sequence ()
These are the arguments to function calls that have already returned. */
int pending_stack_adjust;
-/* Nonzero means stack pops must not be deferred, and deferred stack
- pops must not be output. It is nonzero inside a function call,
- inside a conditional expression, inside a statement expression,
- and in other cases as well. */
+/* Under some ABIs, it is the caller's responsibility to pop arguments
+ pushed for function calls. A naive implementation would simply pop
+ the arguments immediately after each call. However, if several
+ function calls are made in a row, it is typically cheaper to pop
+ all the arguments after all of the calls are complete since a
+ single pop instruction can be used. Therefore, GCC attempts to
+ defer popping the arguments until absolutely necessary. (For
+ example, at the end of a conditional, the arguments must be popped,
+ since code outside the conditional won't know whether or not the
+ arguments need to be popped.)
+
+ When INHIBIT_DEFER_POP is non-zero, however, the compiler does not
+ attempt to defer pops. Instead, the stack is popped immediately
+ after each call. Rather then setting this variable directly, use
+ NO_DEFER_POP and OK_DEFER_POP. */
int inhibit_defer_pop;
/* Nonzero means __builtin_saveregs has already been done in this function.
function. */
extern int current_function_check_memory_usage;
-/* Nonzero means stack pops must not be deferred, and deferred stack
- pops must not be output. It is nonzero inside a function call,
- inside a conditional expression, inside a statement expression,
- and in other cases as well. */
+/* Under some ABIs, it is the caller's responsibility to pop arguments
+ pushed for function calls. A naive implementation would simply pop
+ the arguments immediately after each call. However, if several
+ function calls are made in a row, it is typically cheaper to pop
+ all the arguments after all of the calls are complete since a
+ single pop instruction can be used. Therefore, GCC attempts to
+ defer popping the arguments until absolutely necessary. (For
+ example, at the end of a conditional, the arguments must be popped,
+ since code outside the conditional won't know whether or not the
+ arguments need to be popped.)
+
+ When INHIBIT_DEFER_POP is non-zero, however, the compiler does not
+ attempt to defer pops. Instead, the stack is popped immediately
+ after each call. Rather then setting this variable directly, use
+ NO_DEFER_POP and OK_DEFER_POP. */
extern int inhibit_defer_pop;
+/* Prevent the compiler from deferring stack pops. See
+ inhibit_defer_pop for more information. */
+#define NO_DEFER_POP (inhibit_defer_pop += 1)
+
+/* Allow the compiler to defer stack pops. See inhibit_defer_pop for
+ more information. */
+#define OK_DEFER_POP (inhibit_defer_pop -= 1)
+
/* Number of function calls seen so far in current function. */
extern int function_call_count;
extern tree nonlocal_labels;
#endif
-#define NO_DEFER_POP (inhibit_defer_pop += 1)
-#define OK_DEFER_POP (inhibit_defer_pop -= 1)
-
/* Number of units that we should eventually pop off the stack.
These are the arguments to function calls that have already returned. */
extern int pending_stack_adjust;
projects / thirdparty / gcc.git / commitdiff
