/* Generic sibling call optimization support
- Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
-This file is part of GNU CC.
+This file is part of GCC.
-GNU CC is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
-GNU CC is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU General Public License for more details.
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
You should have received a copy of the GNU General Public License
-along with GNU CC; see the file COPYING. If not, write to
-the Free Software Foundation, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA. */
+along with GCC; see the file COPYING. If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA
+02111-1307, USA. */
#include "config.h"
#include "system.h"
#include "basic-block.h"
#include "output.h"
#include "except.h"
+#include "tree.h"
+
+/* In case alternate_exit_block contains copy from pseudo, to return value,
+ record the pseudo here. In such case the pseudo must be set to function
+ return in the sibcall sequence. */
+static rtx return_value_pseudo;
static int identify_call_return_value PARAMS ((rtx, rtx *, rtx *));
-static rtx skip_copy_to_return_value PARAMS ((rtx, rtx, rtx));
+static rtx skip_copy_to_return_value PARAMS ((rtx));
static rtx skip_use_of_return_value PARAMS ((rtx, enum rtx_code));
static rtx skip_stack_adjustment PARAMS ((rtx));
static rtx skip_pic_restore PARAMS ((rtx));
static rtx skip_jump_insn PARAMS ((rtx));
+static int call_ends_block_p PARAMS ((rtx, rtx));
static int uses_addressof PARAMS ((rtx));
static int sequence_uses_addressof PARAMS ((rtx));
static void purge_reg_equiv_notes PARAMS ((void));
+static void purge_mem_unchanging_flag PARAMS ((rtx));
+static rtx skip_unreturned_value PARAMS ((rtx));
/* Examine a CALL_PLACEHOLDER pattern and determine where the call's
return value is located. P_HARD_RETURN receives the hard register
/* If we didn't get a single hard register (e.g. a parallel), give up. */
if (GET_CODE (hard) != REG)
return 0;
-
+
/* Stack adjustment done after call may appear here. */
insn = skip_stack_adjustment (insn);
if (! insn)
insn = NEXT_INSN (insn);
if (! insn)
return 0;
-
+
/* We're looking for a source of the hard return register. */
set = single_set (insn);
if (! set || SET_SRC (set) != hard)
copy. Otherwise return ORIG_INSN. */
static rtx
-skip_copy_to_return_value (orig_insn, hardret, softret)
+skip_copy_to_return_value (orig_insn)
rtx orig_insn;
- rtx hardret, softret;
{
rtx insn, set = NULL_RTX;
+ rtx hardret, softret;
+
+ /* If there is no return value, we have nothing to do. */
+ if (! identify_call_return_value (PATTERN (orig_insn), &hardret, &softret))
+ return orig_insn;
insn = next_nonnote_insn (orig_insn);
if (! insn)
if (! set)
return orig_insn;
+ if (return_value_pseudo)
+ {
+ if (SET_DEST (set) == return_value_pseudo
+ && SET_SRC (set) == softret)
+ return insn;
+ return orig_insn;
+ }
+
/* The destination must be the same as the called function's return
value to ensure that any return value is put in the same place by the
- current function and the function we're calling.
+ current function and the function we're calling.
Further, the source must be the same as the pseudo into which the
called function's return value was copied. Otherwise we're returning
&& SET_SRC (set) == softret)
return insn;
+ /* Recognize the situation when the called function's return value
+ is copied in two steps: first into an intermediate pseudo, then
+ the into the calling functions return value register. */
+
+ if (REG_P (SET_DEST (set))
+ && SET_SRC (set) == softret)
+ {
+ rtx x = SET_DEST (set);
+
+ insn = next_nonnote_insn (insn);
+ if (! insn)
+ return orig_insn;
+
+ set = single_set (insn);
+ if (! set)
+ return orig_insn;
+
+ if (SET_DEST (set) == current_function_return_rtx
+ && REG_P (SET_DEST (set))
+ && OUTGOING_REGNO (REGNO (SET_DEST (set))) == REGNO (hardret)
+ && SET_SRC (set) == x)
+ return insn;
+ }
+
/* It did not look like a copy of the return value, so return the
same insn we were passed. */
return orig_insn;
return orig_insn;
}
+/* In case function does not return value, we get clobber of pseudo followed
+ by set to hard return value. */
+static rtx
+skip_unreturned_value (orig_insn)
+ rtx orig_insn;
+{
+ rtx insn = next_nonnote_insn (orig_insn);
+
+ /* Skip possible clobber of pseudo return register. */
+ if (insn
+ && GET_CODE (insn) == INSN
+ && GET_CODE (PATTERN (insn)) == CLOBBER
+ && REG_P (XEXP (PATTERN (insn), 0))
+ && (REGNO (XEXP (PATTERN (insn), 0)) >= FIRST_PSEUDO_REGISTER))
+ {
+ rtx set_insn = next_nonnote_insn (insn);
+ rtx set;
+ if (!set_insn)
+ return insn;
+ set = single_set (set_insn);
+ if (!set
+ || SET_SRC (set) != XEXP (PATTERN (insn), 0)
+ || SET_DEST (set) != current_function_return_rtx)
+ return insn;
+ return set_insn;
+ }
+ return orig_insn;
+}
+
/* If the first real insn after ORIG_INSN adjusts the stack pointer
by a constant, return the insn with the stack pointer adjustment.
Otherwise return ORIG_INSN. */
return orig_insn;
}
+\f
+/* Using the above functions, see if INSN, skipping any of the above,
+ goes all the way to END, the end of a basic block. Return 1 if so. */
+
+static int
+call_ends_block_p (insn, end)
+ rtx insn;
+ rtx end;
+{
+ rtx new_insn;
+ /* END might be a note, so get the last nonnote insn of the block. */
+ end = next_nonnote_insn (PREV_INSN (end));
+
+ /* If the call was the end of the block, then we're OK. */
+ if (insn == end)
+ return 1;
+
+ /* Skip over copying from the call's return value pseudo into
+ this function's hard return register and if that's the end
+ of the block, we're OK. */
+ new_insn = skip_copy_to_return_value (insn);
+
+ /* In case we return value in pseudo, we must set the pseudo to
+ return value of called function, otherwise we are returning
+ something else. */
+ if (return_value_pseudo && insn == new_insn)
+ return 0;
+ insn = new_insn;
+
+ if (insn == end)
+ return 1;
+
+ /* Skip any stack adjustment. */
+ insn = skip_stack_adjustment (insn);
+ if (insn == end)
+ return 1;
+
+ /* Skip over a CLOBBER of the return value as a hard reg. */
+ insn = skip_use_of_return_value (insn, CLOBBER);
+ if (insn == end)
+ return 1;
+
+ /* Skip over a CLOBBER of the return value as a hard reg. */
+ insn = skip_unreturned_value (insn);
+ if (insn == end)
+ return 1;
+
+ /* Skip over a USE of the return value (as a hard reg). */
+ insn = skip_use_of_return_value (insn, USE);
+ if (insn == end)
+ return 1;
+
+ /* Skip over a JUMP_INSN at the end of the block. If that doesn't end the
+ block, the original CALL_INSN didn't. */
+ insn = skip_jump_insn (insn);
+ return insn == end;
+}
/* Scan the rtx X for ADDRESSOF expressions or
current_function_internal_arg_pointer registers.
if (code == MEM)
return 0;
- /* Scan all subexpressions. */
+ /* Scan all subexpressions. */
fmt = GET_RTX_FORMAT (code);
for (i = 0; i < GET_RTX_LENGTH (code); i++, fmt++)
{
}
/* Scan the sequence of insns in SEQ to see if any have an ADDRESSOF
- rtl expression or current_function_internal_arg_pointer occurences
+ rtl expression or current_function_internal_arg_pointer occurrences
not enclosed within a MEM. If an ADDRESSOF expression or
current_function_internal_arg_pointer is found, return nonzero, otherwise
return zero.
}
}
+/* Clear RTX_UNCHANGING_P flag of incoming argument MEMs. */
+
+static void
+purge_mem_unchanging_flag (x)
+ rtx x;
+{
+ RTX_CODE code;
+ int i, j;
+ const char *fmt;
+
+ if (x == NULL_RTX)
+ return;
+
+ code = GET_CODE (x);
+
+ if (code == MEM)
+ {
+ if (RTX_UNCHANGING_P (x)
+ && (XEXP (x, 0) == current_function_internal_arg_pointer
+ || (GET_CODE (XEXP (x, 0)) == PLUS
+ && XEXP (XEXP (x, 0), 0) ==
+ current_function_internal_arg_pointer
+ && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT)))
+ RTX_UNCHANGING_P (x) = 0;
+ return;
+ }
+
+ /* Scan all subexpressions. */
+ fmt = GET_RTX_FORMAT (code);
+ for (i = 0; i < GET_RTX_LENGTH (code); i++, fmt++)
+ {
+ if (*fmt == 'e')
+ purge_mem_unchanging_flag (XEXP (x, i));
+ else if (*fmt == 'E')
+ for (j = 0; j < XVECLEN (x, i); j++)
+ purge_mem_unchanging_flag (XVECEXP (x, i, j));
+ }
+}
+
/* Replace the CALL_PLACEHOLDER with one of its children. INSN should be
the CALL_PLACEHOLDER insn; USE tells which child to use. */
sibcall_use_t use;
{
if (use == sibcall_use_tail_recursion)
- emit_insns_before (XEXP (PATTERN (insn), 2), insn);
+ emit_insn_before (XEXP (PATTERN (insn), 2), insn);
else if (use == sibcall_use_sibcall)
- emit_insns_before (XEXP (PATTERN (insn), 1), insn);
+ emit_insn_before (XEXP (PATTERN (insn), 1), insn);
else if (use == sibcall_use_normal)
- emit_insns_before (XEXP (PATTERN (insn), 0), insn);
+ emit_insn_before (XEXP (PATTERN (insn), 0), insn);
else
- abort();
+ abort ();
/* Turn off LABEL_PRESERVE_P for the tail recursion label if it
exists. We only had to set it long enough to keep the jump
pass above from deleting it as unused. */
if (XEXP (PATTERN (insn), 3))
LABEL_PRESERVE_P (XEXP (PATTERN (insn), 3)) = 0;
-
- /* "Delete" the placeholder insn. */
- PUT_CODE (insn, NOTE);
- NOTE_SOURCE_FILE (insn) = 0;
- NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
+
+ /* "Delete" the placeholder insn. */
+ remove_insn (insn);
}
/* Given a (possibly empty) set of potential sibling or tail recursion call
{
rtx insn, insns;
basic_block alternate_exit = EXIT_BLOCK_PTR;
- int current_function_uses_addressof;
+ bool no_sibcalls_this_function = false;
int successful_sibling_call = 0;
int replaced_call_placeholder = 0;
edge e;
insns = get_insns ();
- /* We do not perform these calls when flag_exceptions is true, so this
- is probably a NOP at the current time. However, we may want to support
- sibling and tail recursion optimizations in the future, so let's plan
- ahead and find all the EH labels. */
- find_exception_handler_labels ();
-
- /* Run a jump optimization pass to clean up the CFG. We primarily want
- this to thread jumps so that it is obvious which blocks jump to the
- epilouge. */
- jump_optimize_minimal (insns);
-
- /* We need cfg information to determine which blocks are succeeded
- only by the epilogue. */
- find_basic_blocks (insns, max_reg_num (), 0);
- cleanup_cfg (insns);
+ cleanup_cfg (CLEANUP_PRE_SIBCALL | CLEANUP_PRE_LOOP);
/* If there are no basic blocks, then there is nothing to do. */
if (n_basic_blocks == 0)
return;
+ /* If we are using sjlj exceptions, we may need to add a call to
+ _Unwind_SjLj_Unregister at exit of the function. Which means
+ that we cannot do any sibcall transformations. */
+ if (USING_SJLJ_EXCEPTIONS && current_function_has_exception_handlers ())
+ no_sibcalls_this_function = true;
+
+ return_value_pseudo = NULL_RTX;
+
/* Find the exit block.
It is possible that we have blocks which can reach the exit block
/* Walk forwards through the last normal block and see if it
does nothing except fall into the exit block. */
- for (insn = BLOCK_HEAD (n_basic_blocks - 1);
+ for (insn = EXIT_BLOCK_PTR->prev_bb->head;
insn;
insn = NEXT_INSN (insn))
{
+ rtx set;
/* This should only happen once, at the start of this block. */
if (GET_CODE (insn) == CODE_LABEL)
continue;
&& GET_CODE (PATTERN (insn)) == USE)
continue;
+ /* Exit block also may contain copy from pseudo containing
+ return value to hard register. */
+ if (GET_CODE (insn) == INSN
+ && (set = single_set (insn))
+ && SET_DEST (set) == current_function_return_rtx
+ && REG_P (SET_SRC (set))
+ && !return_value_pseudo)
+ {
+ return_value_pseudo = SET_SRC (set);
+ continue;
+ }
+
break;
}
valid alternate exit block. */
if (insn == NULL)
alternate_exit = e->src;
+ else
+ return_value_pseudo = NULL;
}
/* If the function uses ADDRESSOF, we can't (easily) determine
at this point if the value will end up on the stack. */
- current_function_uses_addressof = sequence_uses_addressof (insns);
+ no_sibcalls_this_function |= sequence_uses_addressof (insns);
/* Walk the insn chain and find any CALL_PLACEHOLDER insns. We need to
select one of the insn sequences attached to each CALL_PLACEHOLDER.
{
int sibcall = (XEXP (PATTERN (insn), 1) != NULL_RTX);
int tailrecursion = (XEXP (PATTERN (insn), 2) != NULL_RTX);
- basic_block succ_block, call_block;
- rtx temp, hardret, softret;
-
- /* We must be careful with stack slots which are live at
- potential optimization sites.
-
- ?!? This test is overly conservative and will be replaced. */
- if (frame_offset)
- goto failure;
-
- /* Taking the address of a local variable is fatal to tail
- recursion if the address is used by the recursive call. */
- if (current_function_uses_addressof)
- goto failure;
+ basic_block call_block = BLOCK_FOR_INSN (insn);
/* alloca (until we have stack slot life analysis) inhibits
sibling call optimizations, but not tail recursion.
Similarly if we use varargs or stdarg since they implicitly
may take the address of an argument. */
- if (current_function_calls_alloca
- || current_function_varargs || current_function_stdarg)
+ if (current_function_calls_alloca || current_function_stdarg)
sibcall = 0;
- call_block = BLOCK_FOR_INSN (insn);
-
- /* If the block has more than one successor, then we can not
- perform sibcall or tail recursion optimizations. */
- if (call_block->succ == NULL
- || call_block->succ->succ_next != NULL)
- goto failure;
-
- /* If the single successor is not the exit block, then we can not
- perform sibcall or tail recursion optimizations.
-
- Note that this test combined with the previous is sufficient
- to prevent tail call optimization in the presense of active
- exception handlers. */
- succ_block = call_block->succ->dest;
- if (succ_block != EXIT_BLOCK_PTR && succ_block != alternate_exit)
- goto failure;
-
- /* If the call was the end of the block, then we're OK. */
- temp = insn;
- if (temp == call_block->end)
- goto success;
-
- /* Skip over copying from the call's return value pseudo into
- this function's hard return register. */
- if (identify_call_return_value (PATTERN (insn), &hardret, &softret))
- {
- temp = skip_copy_to_return_value (temp, hardret, softret);
- if (temp == call_block->end)
- goto success;
- }
-
- /* Skip any stack adjustment. */
- temp = skip_stack_adjustment (temp);
- if (temp == call_block->end)
- goto success;
-
- /* Skip over a CLOBBER of the return value (as a hard reg). */
- temp = skip_use_of_return_value (temp, CLOBBER);
- if (temp == call_block->end)
- goto success;
-
- /* Skip over a USE of the return value (as a hard reg). */
- temp = skip_use_of_return_value (temp, USE);
- if (temp == call_block->end)
- goto success;
-
- /* Skip over the JUMP_INSN at the end of the block. */
- temp = skip_jump_insn (temp);
- if (GET_CODE (temp) == NOTE)
- temp = next_nonnote_insn (temp);
- if (temp == call_block->end)
- goto success;
-
- /* There are operations at the end of the block which we must
- execute after returning from the function call. So this call
- can not be optimized. */
-failure:
- sibcall = 0, tailrecursion = 0;
-success:
+ /* See if there are any reasons we can't perform either sibling or
+ tail call optimizations. We must be careful with stack slots
+ which are live at potential optimization sites. */
+ if (no_sibcalls_this_function
+ /* ??? Overly conservative. */
+ || frame_offset
+ /* Any function that calls setjmp might have longjmp called from
+ any called function. ??? We really should represent this
+ properly in the CFG so that this needn't be special cased. */
+ || current_function_calls_setjmp
+ /* Can't if more than one successor or single successor is not
+ exit block. These two tests prevent tail call optimization
+ in the presense of active exception handlers. */
+ || call_block->succ == NULL
+ || call_block->succ->succ_next != NULL
+ || (call_block->succ->dest != EXIT_BLOCK_PTR
+ && call_block->succ->dest != alternate_exit)
+ /* If this call doesn't end the block, there are operations at
+ the end of the block which we must execute after returning. */
+ || ! call_ends_block_p (insn, call_block->end))
+ sibcall = 0, tailrecursion = 0;
/* Select a set of insns to implement the call and emit them.
Tail recursion is the most efficient, so select it over
a tail/sibling call. */
-
if (sibcall)
successful_sibling_call = 1;
+
replaced_call_placeholder = 1;
- replace_call_placeholder (insn,
- tailrecursion != 0
+ replace_call_placeholder (insn,
+ tailrecursion != 0
? sibcall_use_tail_recursion
: sibcall != 0
? sibcall_use_sibcall
}
}
- /* A sibling call sequence invalidates any REG_EQUIV notes made for
- this function's incoming arguments.
+ if (successful_sibling_call)
+ {
+ rtx insn;
+ tree arg;
- At the start of RTL generation we know the only REG_EQUIV notes
- in the rtl chain are those for incoming arguments, so we can safely
- flush any REG_EQUIV note.
+ /* A sibling call sequence invalidates any REG_EQUIV notes made for
+ this function's incoming arguments.
- This is (slight) overkill. We could keep track of the highest argument
- we clobber and be more selective in removing notes, but it does not
- seem to be worth the effort. */
- if (successful_sibling_call)
- purge_reg_equiv_notes ();
+ At the start of RTL generation we know the only REG_EQUIV notes
+ in the rtl chain are those for incoming arguments, so we can safely
+ flush any REG_EQUIV note.
+
+ This is (slight) overkill. We could keep track of the highest
+ argument we clobber and be more selective in removing notes, but it
+ does not seem to be worth the effort. */
+ purge_reg_equiv_notes ();
+
+ /* A sibling call sequence also may invalidate RTX_UNCHANGING_P
+ flag of some incoming arguments MEM RTLs, because it can write into
+ those slots. We clear all those bits now.
+
+ This is (slight) overkill, we could keep track of which arguments
+ we actually write into. */
+ for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
+ {
+ if (INSN_P (insn))
+ purge_mem_unchanging_flag (PATTERN (insn));
+ }
+
+ /* Similarly, invalidate RTX_UNCHANGING_P for any incoming
+ arguments passed in registers. */
+ for (arg = DECL_ARGUMENTS (current_function_decl);
+ arg;
+ arg = TREE_CHAIN (arg))
+ {
+ if (REG_P (DECL_RTL (arg)))
+ RTX_UNCHANGING_P (DECL_RTL (arg)) = false;
+ }
+ }
- /* There may have been NOTE_INSN_BLOCK_{BEGIN,END} notes in the
+ /* There may have been NOTE_INSN_BLOCK_{BEGIN,END} notes in the
CALL_PLACEHOLDER alternatives that we didn't emit. Rebuild the
lexical block tree to correspond to the notes that still exist. */
if (replaced_call_placeholder)
/* This information will be invalid after inline expansion. Kill it now. */
free_basic_block_vars (0);
+ free_EXPR_LIST_list (&tail_recursion_label_list);
}
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