/* Generic sibling call optimization support
- Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
This file is part of GNU CC.
#include "except.h"
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));
/* Examine a CALL_PLACEHOLDER pattern and determine where the call's
return value is located. P_HARD_RETURN receives the hard register
{
rtx insn, set, hard, soft;
- /* Search forward through the "normal" call sequence to the CALL insn. */
insn = XEXP (cp, 0);
- while (GET_CODE (insn) != CALL_INSN)
+ /* Search backward through the "normal" call sequence to the CALL insn. */
+ while (NEXT_INSN (insn))
insn = NEXT_INSN (insn);
+ while (GET_CODE (insn) != CALL_INSN)
+ insn = PREV_INSN (insn);
/* Assume the pattern is (set (dest) (call ...)), or that the first
member of a parallel is. This is the hard return register used
if (GET_CODE (hard) != REG)
return 0;
+ /* Stack adjustment done after call may appear here. */
+ insn = skip_stack_adjustment (insn);
+ if (! insn)
+ return 0;
+
+ /* Restore of GP register may appear here. */
+ insn = skip_pic_restore (insn);
+ if (! insn)
+ return 0;
+
/* If there's nothing after, there's no soft return value. */
insn = NEXT_INSN (insn);
if (! insn)
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 (insn)
set = single_set (insn);
- /* The source must be the same as the current 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. The destination register
- must be a pseudo. */
if (insn
&& set
&& GET_CODE (SET_SRC (set)) == PLUS
&& SET_DEST (set) == stack_pointer_rtx)
return insn;
- /* It did not look like a copy of the return value, so return the
- same insn we were passed. */
+ return orig_insn;
+}
+
+/* If the first real insn after ORIG_INSN sets the pic register,
+ return it. Otherwise return ORIG_INSN. */
+
+static rtx
+skip_pic_restore (orig_insn)
+ rtx orig_insn;
+{
+ rtx insn, set = NULL_RTX;
+
+ insn = next_nonnote_insn (orig_insn);
+
+ if (insn)
+ set = single_set (insn);
+
+ if (insn && set && SET_DEST (set) == pic_offset_table_rtx)
+ return insn;
+
return orig_insn;
}
if (insn
&& GET_CODE (insn) == JUMP_INSN
- && simplejump_p (insn))
+ && any_uncondjump_p (insn))
return 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;
+{
+ /* 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. */
+ insn = skip_copy_to_return_value (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 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 an ADDRESSOF expressions. Return nonzero if an ADDRESSOF
- expresion is found, else return zero. */
+/* Scan the rtx X for ADDRESSOF expressions or
+ current_function_internal_arg_pointer registers.
+ Return nonzero if an ADDRESSOF or current_function_internal_arg_pointer
+ is found outside of some MEM expression, else return zero. */
static int
uses_addressof (x)
code = GET_CODE (x);
- if (code == ADDRESSOF)
+ if (code == ADDRESSOF || x == current_function_internal_arg_pointer)
return 1;
+ if (code == MEM)
+ return 0;
+
/* 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. If an ADDRESSOF expression is found, return nonzero,
- else return zero.
+ rtl expression or current_function_internal_arg_pointer occurences
+ not enclosed within a MEM. If an ADDRESSOF expression or
+ current_function_internal_arg_pointer is found, return nonzero, otherwise
+ return zero.
This function handles CALL_PLACEHOLDERs which contain multiple sequences
of insns. */
rtx insn;
for (insn = seq; insn; insn = NEXT_INSN (insn))
- if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
+ if (INSN_P (insn))
{
/* If this is a CALL_PLACEHOLDER, then recursively call ourselves
with each nonempty sequence attached to the CALL_PLACEHOLDER. */
}
}
+/* 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. */
/* 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 ();
/* If there are no basic blocks, then there is nothing to do. */
if (n_basic_blocks == 0)
{
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;
+ 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 have ADDRESSOF expressions.
-
Similarly if we use varargs or stdarg since they implicitly
may take the address of an argument. */
- if (current_function_calls_alloca || current_function_uses_addressof
+ if (current_function_calls_alloca
|| current_function_varargs || 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. ?!? The first
+ test is overly conservative and should be replaced. */
+ if (frame_offset
+ /* Can't take address of local var if used by recursive call. */
+ || current_function_uses_addressof
+ /* 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
}
}
- /* A sibling call sequence invalidates any REG_EQUIV notes made for
- this function's incoming arguments.
-
- 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. */
if (successful_sibling_call)
- purge_reg_equiv_notes ();
+ {
+ rtx insn;
+
+ /* A sibling call sequence invalidates any REG_EQUIV notes made for
+ this function's incoming arguments.
+
+ 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 (GET_CODE (insn) == NOTE)
+ {
+ if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
+ break;
+ }
+ else if (INSN_P (insn))
+ purge_mem_unchanging_flag (PATTERN (insn));
+ }
+ }
/* There may have been NOTE_INSN_BLOCK_{BEGIN,END} notes in the
CALL_PLACEHOLDER alternatives that we didn't emit. Rebuild the
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