diff options
Diffstat (limited to 'gcc/expr.h')
| -rw-r--r-- | gcc/expr.h | 30 |
1 files changed, 23 insertions, 7 deletions
@@ -95,12 +95,31 @@ extern rtx current_function_internal_arg_pointer; 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; @@ -126,9 +145,6 @@ extern rtx nonlocal_goto_stack_level; 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; |