diff options
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. |