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author | Mark Mitchell <mark@codesourcery.com> | 1999-04-29 23:01:29 +0000 |
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committer | Mark Mitchell <mmitchel@gcc.gnu.org> | 1999-04-29 23:01:29 +0000 |
commit | 5c7a310f81ad5609a1830d4d156ef90f3a35d764 (patch) | |
tree | 556b4266f6a4292a1085b6bcb6c75790cd0cf08f /gcc/expr.c | |
parent | 1a6580ec80d9c0dba5970a7541162faffb48a613 (diff) | |
download | gcc-5c7a310f81ad5609a1830d4d156ef90f3a35d764.zip gcc-5c7a310f81ad5609a1830d4d156ef90f3a35d764.tar.gz gcc-5c7a310f81ad5609a1830d4d156ef90f3a35d764.tar.bz2 |
emit-rtl.c (start_sequence): Expand comments.
* 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
Diffstat (limited to 'gcc/expr.c')
-rw-r--r-- | gcc/expr.c | 19 |
1 files changed, 15 insertions, 4 deletions
@@ -87,10 +87,21 @@ int do_preexpand_calls = 1; 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. |