diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 11 | ||||
| -rw-r--r-- | gcc/emit-rtl.c | 30 | ||||
| -rw-r--r-- | gcc/expr.c | 19 | ||||
| -rw-r--r-- | gcc/expr.h | 30 |
4 files changed, 72 insertions, 18 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index bfd1e67..c924547 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,14 @@ +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' diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c index b1e2d3d..2aa51ac 100644 --- a/gcc/emit-rtl.c +++ b/gcc/emit-rtl.c @@ -3284,7 +3284,13 @@ emit (x) abort (); } -/* 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 () @@ -3311,8 +3317,9 @@ 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) @@ -3323,8 +3330,9 @@ 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) @@ -3378,8 +3386,16 @@ pop_topmost_sequence () /* 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 () @@ -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. @@ -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; |