/* SSA Jump Threading
- Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
+ Copyright (C) 2005-2015 Free Software Foundation, Inc.
Contributed by Jeff Law <law@redhat.com>
This file is part of GCC.
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)
+the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to
-the Free Software Foundation, 51 Franklin Street, Fifth Floor,
-Boston, MA 02110-1301, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
+#include "alias.h"
+#include "symtab.h"
#include "tree.h"
+#include "fold-const.h"
#include "flags.h"
-#include "rtl.h"
#include "tm_p.h"
-#include "ggc.h"
+#include "predict.h"
+#include "hard-reg-set.h"
+#include "function.h"
+#include "dominance.h"
#include "basic-block.h"
#include "cfgloop.h"
-#include "output.h"
-#include "expr.h"
-#include "function.h"
-#include "diagnostic.h"
#include "timevar.h"
-#include "tree-dump.h"
-#include "tree-flow.h"
-#include "domwalk.h"
-#include "real.h"
-#include "tree-pass.h"
+#include "dumpfile.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "gimple-expr.h"
+#include "gimple.h"
+#include "gimple-iterator.h"
+#include "gimple-ssa.h"
+#include "tree-cfg.h"
+#include "tree-phinodes.h"
+#include "ssa-iterators.h"
+#include "stringpool.h"
+#include "tree-ssanames.h"
#include "tree-ssa-propagate.h"
+#include "tree-ssa-threadupdate.h"
#include "langhooks.h"
#include "params.h"
+#include "tree-ssa-scopedtables.h"
+#include "tree-ssa-threadedge.h"
+#include "tree-ssa-loop.h"
+#include "builtins.h"
+#include "cfg.h"
+#include "cfganal.h"
/* To avoid code explosion due to jump threading, we limit the
number of statements we are going to copy. This variable
to copy as part of the jump threading process. */
static int stmt_count;
+/* Array to record value-handles per SSA_NAME. */
+vec<tree> ssa_name_values;
+
+/* Set the value for the SSA name NAME to VALUE. */
+
+void
+set_ssa_name_value (tree name, tree value)
+{
+ if (SSA_NAME_VERSION (name) >= ssa_name_values.length ())
+ ssa_name_values.safe_grow_cleared (SSA_NAME_VERSION (name) + 1);
+ if (value && TREE_OVERFLOW_P (value))
+ value = drop_tree_overflow (value);
+ ssa_name_values[SSA_NAME_VERSION (name)] = value;
+}
+
+/* Initialize the per SSA_NAME value-handles array. Returns it. */
+void
+threadedge_initialize_values (void)
+{
+ gcc_assert (!ssa_name_values.exists ());
+ ssa_name_values.create (num_ssa_names);
+}
+
+/* Free the per SSA_NAME value-handle array. */
+void
+threadedge_finalize_values (void)
+{
+ ssa_name_values.release ();
+}
+
/* Return TRUE if we may be able to thread an incoming edge into
BB to an outgoing edge from BB. Return FALSE otherwise. */
bool
potentially_threadable_block (basic_block bb)
{
- block_stmt_iterator bsi;
-
+ gimple_stmt_iterator gsi;
+
+ /* Special case. We can get blocks that are forwarders, but are
+ not optimized away because they forward from outside a loop
+ to the loop header. We want to thread through them as we can
+ sometimes thread to the loop exit, which is obviously profitable.
+ the interesting case here is when the block has PHIs. */
+ if (gsi_end_p (gsi_start_nondebug_bb (bb))
+ && !gsi_end_p (gsi_start_phis (bb)))
+ return true;
+
/* If BB has a single successor or a single predecessor, then
there is no threading opportunity. */
if (single_succ_p (bb) || single_pred_p (bb))
/* If BB does not end with a conditional, switch or computed goto,
then there is no threading opportunity. */
- bsi = bsi_last (bb);
- if (bsi_end_p (bsi)
- || ! bsi_stmt (bsi)
- || (TREE_CODE (bsi_stmt (bsi)) != COND_EXPR
- && TREE_CODE (bsi_stmt (bsi)) != GOTO_EXPR
- && TREE_CODE (bsi_stmt (bsi)) != SWITCH_EXPR))
+ gsi = gsi_last_bb (bb);
+ if (gsi_end_p (gsi)
+ || ! gsi_stmt (gsi)
+ || (gimple_code (gsi_stmt (gsi)) != GIMPLE_COND
+ && gimple_code (gsi_stmt (gsi)) != GIMPLE_GOTO
+ && gimple_code (gsi_stmt (gsi)) != GIMPLE_SWITCH))
return false;
return true;
BB. If no such ASSERT_EXPR is found, return OP. */
static tree
-lhs_of_dominating_assert (tree op, basic_block bb, tree stmt)
+lhs_of_dominating_assert (tree op, basic_block bb, gimple stmt)
{
imm_use_iterator imm_iter;
- tree use_stmt;
+ gimple use_stmt;
use_operand_p use_p;
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, op)
{
use_stmt = USE_STMT (use_p);
if (use_stmt != stmt
- && TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
- && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == ASSERT_EXPR
- && TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0) == op
- && dominated_by_p (CDI_DOMINATORS, bb, bb_for_stmt (use_stmt)))
+ && gimple_assign_single_p (use_stmt)
+ && TREE_CODE (gimple_assign_rhs1 (use_stmt)) == ASSERT_EXPR
+ && TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0) == op
+ && dominated_by_p (CDI_DOMINATORS, bb, gimple_bb (use_stmt)))
{
- return GIMPLE_STMT_OPERAND (use_stmt, 0);
+ return gimple_assign_lhs (use_stmt);
}
}
return op;
}
-
-/* We record temporary equivalences created by PHI nodes or
- statements within the target block. Doing so allows us to
- identify more jump threading opportunities, even in blocks
- with side effects.
-
- We keep track of those temporary equivalences in a stack
- structure so that we can unwind them when we're done processing
- a particular edge. This routine handles unwinding the data
- structures. */
-
-static void
-remove_temporary_equivalences (VEC(tree, heap) **stack)
-{
- while (VEC_length (tree, *stack) > 0)
- {
- tree prev_value, dest;
-
- dest = VEC_pop (tree, *stack);
-
- /* A NULL value indicates we should stop unwinding, otherwise
- pop off the next entry as they're recorded in pairs. */
- if (dest == NULL)
- break;
-
- prev_value = VEC_pop (tree, *stack);
- SSA_NAME_VALUE (dest) = prev_value;
- }
-}
-
-/* Record a temporary equivalence, saving enough information so that
- we can restore the state of recorded equivalences when we're
- done processing the current edge. */
-
-static void
-record_temporary_equivalence (tree x, tree y, VEC(tree, heap) **stack)
-{
- tree prev_x = SSA_NAME_VALUE (x);
-
- if (TREE_CODE (y) == SSA_NAME)
- {
- tree tmp = SSA_NAME_VALUE (y);
- y = tmp ? tmp : y;
- }
-
- SSA_NAME_VALUE (x) = y;
- VEC_reserve (tree, heap, *stack, 2);
- VEC_quick_push (tree, *stack, prev_x);
- VEC_quick_push (tree, *stack, x);
-}
-
/* Record temporary equivalences created by PHIs at the target of the
- edge E. Record unwind information for the equivalences onto STACK.
+ edge E. Record unwind information for the equivalences onto STACK.
If a PHI which prevents threading is encountered, then return FALSE
- indicating we should not thread this edge, else return TRUE. */
+ indicating we should not thread this edge, else return TRUE.
+
+ If SRC_MAP/DST_MAP exist, then mark the source and destination SSA_NAMEs
+ of any equivalences recorded. We use this to make invalidation after
+ traversing back edges less painful. */
static bool
-record_temporary_equivalences_from_phis (edge e, VEC(tree, heap) **stack)
+record_temporary_equivalences_from_phis (edge e, const_and_copies *const_and_copies)
{
- tree phi;
+ gphi_iterator gsi;
/* Each PHI creates a temporary equivalence, record them.
These are context sensitive equivalences and will be removed
later. */
- for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
+ for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
{
+ gphi *phi = gsi.phi ();
tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
- tree dst = PHI_RESULT (phi);
+ tree dst = gimple_phi_result (phi);
- /* If the desired argument is not the same as this PHI's result
+ /* If the desired argument is not the same as this PHI's result
and it is set by a PHI in E->dest, then we can not thread
through E->dest. */
if (src != dst
&& TREE_CODE (src) == SSA_NAME
- && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
- && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
+ && gimple_code (SSA_NAME_DEF_STMT (src)) == GIMPLE_PHI
+ && gimple_bb (SSA_NAME_DEF_STMT (src)) == e->dest)
return false;
/* We consider any non-virtual PHI as a statement since it
count result in a constant assignment or copy operation. */
- if (is_gimple_reg (dst))
+ if (!virtual_operand_p (dst))
stmt_count++;
- record_temporary_equivalence (dst, src, stack);
+ const_and_copies->record_const_or_copy (dst, src);
}
return true;
}
+/* Fold the RHS of an assignment statement and return it as a tree.
+ May return NULL_TREE if no simplification is possible. */
+
+static tree
+fold_assignment_stmt (gimple stmt)
+{
+ enum tree_code subcode = gimple_assign_rhs_code (stmt);
+
+ switch (get_gimple_rhs_class (subcode))
+ {
+ case GIMPLE_SINGLE_RHS:
+ return fold (gimple_assign_rhs1 (stmt));
+
+ case GIMPLE_UNARY_RHS:
+ {
+ tree lhs = gimple_assign_lhs (stmt);
+ tree op0 = gimple_assign_rhs1 (stmt);
+ return fold_unary (subcode, TREE_TYPE (lhs), op0);
+ }
+
+ case GIMPLE_BINARY_RHS:
+ {
+ tree lhs = gimple_assign_lhs (stmt);
+ tree op0 = gimple_assign_rhs1 (stmt);
+ tree op1 = gimple_assign_rhs2 (stmt);
+ return fold_binary (subcode, TREE_TYPE (lhs), op0, op1);
+ }
+
+ case GIMPLE_TERNARY_RHS:
+ {
+ tree lhs = gimple_assign_lhs (stmt);
+ tree op0 = gimple_assign_rhs1 (stmt);
+ tree op1 = gimple_assign_rhs2 (stmt);
+ tree op2 = gimple_assign_rhs3 (stmt);
+
+ /* Sadly, we have to handle conditional assignments specially
+ here, because fold expects all the operands of an expression
+ to be folded before the expression itself is folded, but we
+ can't just substitute the folded condition here. */
+ if (gimple_assign_rhs_code (stmt) == COND_EXPR)
+ op0 = fold (op0);
+
+ return fold_ternary (subcode, TREE_TYPE (lhs), op0, op1, op2);
+ }
+
+ default:
+ gcc_unreachable ();
+ }
+}
+
/* Try to simplify each statement in E->dest, ultimately leading to
a simplification of the COND_EXPR at the end of E->dest.
Record unwind information for temporary equivalences onto STACK.
Use SIMPLIFY (a pointer to a callback function) to further simplify
- statements using pass specific information.
+ statements using pass specific information.
We might consider marking just those statements which ultimately
feed the COND_EXPR. It's not clear if the overhead of bookkeeping
If we are able to simplify a statement into the form
SSA_NAME = (SSA_NAME | gimple invariant), then we can record
- a context sensitive equivalency which may help us simplify
+ a context sensitive equivalence which may help us simplify
later statements in E->dest. */
-static tree
+static gimple
record_temporary_equivalences_from_stmts_at_dest (edge e,
- VEC(tree, heap) **stack,
- tree (*simplify) (tree,
- tree))
+ const_and_copies *const_and_copies,
+ tree (*simplify) (gimple,
+ gimple),
+ bool backedge_seen)
{
- block_stmt_iterator bsi;
- tree stmt = NULL;
+ gimple stmt = NULL;
+ gimple_stmt_iterator gsi;
int max_stmt_count;
max_stmt_count = PARAM_VALUE (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS);
we discover. Note any equivalences we discover are context
sensitive (ie, are dependent on traversing E) and must be unwound
when we're finished processing E. */
- for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
+ for (gsi = gsi_start_bb (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
{
tree cached_lhs = NULL;
- stmt = bsi_stmt (bsi);
+ stmt = gsi_stmt (gsi);
/* Ignore empty statements and labels. */
- if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
+ if (gimple_code (stmt) == GIMPLE_NOP
+ || gimple_code (stmt) == GIMPLE_LABEL
+ || is_gimple_debug (stmt))
continue;
/* If the statement has volatile operands, then we assume we
can not thread through this block. This is overly
conservative in some ways. */
- if (TREE_CODE (stmt) == ASM_EXPR && ASM_VOLATILE_P (stmt))
+ if (gimple_code (stmt) == GIMPLE_ASM
+ && gimple_asm_volatile_p (as_a <gasm *> (stmt)))
return NULL;
/* If duplicating this block is going to cause too much code
if (stmt_count > max_stmt_count)
return NULL;
- /* If this is not a GIMPLE_MODIFY_STMT which sets an SSA_NAME to a new
+ /* If this is not a statement that sets an SSA_NAME to a new
value, then do not try to simplify this statement as it will
not simplify in any way that is helpful for jump threading. */
- if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT
- || TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 0)) != SSA_NAME)
- continue;
+ if ((gimple_code (stmt) != GIMPLE_ASSIGN
+ || TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME)
+ && (gimple_code (stmt) != GIMPLE_CALL
+ || gimple_call_lhs (stmt) == NULL_TREE
+ || TREE_CODE (gimple_call_lhs (stmt)) != SSA_NAME))
+ {
+ /* STMT might still have DEFS and we need to invalidate any known
+ equivalences for them.
+
+ Consider if STMT is a GIMPLE_ASM with one or more outputs that
+ feeds a conditional inside a loop. We might derive an equivalence
+ due to the conditional. */
+ tree op;
+ ssa_op_iter iter;
+
+ if (backedge_seen)
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
+ const_and_copies->invalidate (op);
+
+ continue;
+ }
+
+ /* The result of __builtin_object_size depends on all the arguments
+ of a phi node. Temporarily using only one edge produces invalid
+ results. For example
+
+ if (x < 6)
+ goto l;
+ else
+ goto l;
+
+ l:
+ r = PHI <&w[2].a[1](2), &a.a[6](3)>
+ __builtin_object_size (r, 0)
+
+ The result of __builtin_object_size is defined to be the maximum of
+ remaining bytes. If we use only one edge on the phi, the result will
+ change to be the remaining bytes for the corresponding phi argument.
+
+ Similarly for __builtin_constant_p:
+
+ r = PHI <1(2), 2(3)>
+ __builtin_constant_p (r)
+
+ Both PHI arguments are constant, but x ? 1 : 2 is still not
+ constant. */
+
+ if (is_gimple_call (stmt))
+ {
+ tree fndecl = gimple_call_fndecl (stmt);
+ if (fndecl
+ && (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_OBJECT_SIZE
+ || DECL_FUNCTION_CODE (fndecl) == BUILT_IN_CONSTANT_P))
+ {
+ if (backedge_seen)
+ {
+ tree lhs = gimple_get_lhs (stmt);
+ const_and_copies->invalidate (lhs);
+ }
+ continue;
+ }
+ }
/* At this point we have a statement which assigns an RHS to an
SSA_VAR on the LHS. We want to try and simplify this statement
to expose more context sensitive equivalences which in turn may
- allow us to simplify the condition at the end of the loop.
+ allow us to simplify the condition at the end of the loop.
Handle simple copy operations as well as implied copies from
ASSERT_EXPRs. */
- if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == SSA_NAME)
- cached_lhs = GIMPLE_STMT_OPERAND (stmt, 1);
- else if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ASSERT_EXPR)
- cached_lhs = TREE_OPERAND (GIMPLE_STMT_OPERAND (stmt, 1), 0);
+ if (gimple_assign_single_p (stmt)
+ && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)
+ cached_lhs = gimple_assign_rhs1 (stmt);
+ else if (gimple_assign_single_p (stmt)
+ && TREE_CODE (gimple_assign_rhs1 (stmt)) == ASSERT_EXPR)
+ cached_lhs = TREE_OPERAND (gimple_assign_rhs1 (stmt), 0);
else
{
/* A statement that is not a trivial copy or ASSERT_EXPR.
We're going to temporarily copy propagate the operands
and see if that allows us to simplify this statement. */
- tree *copy, pre_fold_expr;
+ tree *copy;
ssa_op_iter iter;
use_operand_p use_p;
unsigned int num, i = 0;
copy[i++] = use;
if (TREE_CODE (use) == SSA_NAME)
tmp = SSA_NAME_VALUE (use);
- if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
+ if (tmp)
SET_USE (use_p, tmp);
}
/* Try to fold/lookup the new expression. Inserting the
- expression into the hash table is unlikely to help
- Sadly, we have to handle conditional assignments specially
- here, because fold expects all the operands of an expression
- to be folded before the expression itself is folded, but we
- can't just substitute the folded condition here. */
- if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == COND_EXPR)
- {
- tree cond = COND_EXPR_COND (GIMPLE_STMT_OPERAND (stmt, 1));
- cond = fold (cond);
- if (cond == boolean_true_node)
- pre_fold_expr = COND_EXPR_THEN (GIMPLE_STMT_OPERAND (stmt, 1));
- else if (cond == boolean_false_node)
- pre_fold_expr = COND_EXPR_ELSE (GIMPLE_STMT_OPERAND (stmt, 1));
- else
- pre_fold_expr = GIMPLE_STMT_OPERAND (stmt, 1);
- }
+ expression into the hash table is unlikely to help. */
+ if (is_gimple_call (stmt))
+ cached_lhs = fold_call_stmt (as_a <gcall *> (stmt), false);
else
- pre_fold_expr = GIMPLE_STMT_OPERAND (stmt, 1);
+ cached_lhs = fold_assignment_stmt (stmt);
- if (pre_fold_expr)
- {
- cached_lhs = fold (pre_fold_expr);
- if (TREE_CODE (cached_lhs) != SSA_NAME
- && !is_gimple_min_invariant (cached_lhs))
- cached_lhs = (*simplify) (stmt, stmt);
- }
+ if (!cached_lhs
+ || (TREE_CODE (cached_lhs) != SSA_NAME
+ && !is_gimple_min_invariant (cached_lhs)))
+ cached_lhs = (*simplify) (stmt, stmt);
/* Restore the statement's original uses/defs. */
i = 0;
}
/* Record the context sensitive equivalence if we were able
- to simplify this statement. */
+ to simplify this statement.
+
+ If we have traversed a backedge at some point during threading,
+ then always enter something here. Either a real equivalence,
+ or a NULL_TREE equivalence which is effectively invalidation of
+ prior equivalences. */
if (cached_lhs
&& (TREE_CODE (cached_lhs) == SSA_NAME
|| is_gimple_min_invariant (cached_lhs)))
- record_temporary_equivalence (GIMPLE_STMT_OPERAND (stmt, 0),
- cached_lhs,
- stack);
+ const_and_copies->record_const_or_copy (gimple_get_lhs (stmt), cached_lhs);
+ else if (backedge_seen)
+ const_and_copies->invalidate (gimple_get_lhs (stmt));
}
return stmt;
}
+/* Once we have passed a backedge in the CFG when threading, we do not want to
+ utilize edge equivalences for simplification purpose. They are no longer
+ necessarily valid. We use this callback rather than the ones provided by
+ DOM/VRP to achieve that effect. */
+static tree
+dummy_simplify (gimple stmt1 ATTRIBUTE_UNUSED, gimple stmt2 ATTRIBUTE_UNUSED)
+{
+ return NULL_TREE;
+}
+
/* Simplify the control statement at the end of the block E->dest.
- To avoid allocating memory unnecessarily, a scratch COND_EXPR
+ To avoid allocating memory unnecessarily, a scratch GIMPLE_COND
is available to use/clobber in DUMMY_COND.
Use SIMPLIFY (a pointer to a callback function) to further simplify
static tree
simplify_control_stmt_condition (edge e,
- tree stmt,
- tree dummy_cond,
- tree (*simplify) (tree, tree),
+ gimple stmt,
+ gcond *dummy_cond,
+ tree (*simplify) (gimple, gimple),
bool handle_dominating_asserts)
{
tree cond, cached_lhs;
-
- if (TREE_CODE (stmt) == COND_EXPR)
- cond = COND_EXPR_COND (stmt);
- else if (TREE_CODE (stmt) == GOTO_EXPR)
- cond = GOTO_DESTINATION (stmt);
- else
- cond = SWITCH_COND (stmt);
+ enum gimple_code code = gimple_code (stmt);
/* For comparisons, we have to update both operands, then try
to simplify the comparison. */
- if (COMPARISON_CLASS_P (cond))
+ if (code == GIMPLE_COND)
{
tree op0, op1;
enum tree_code cond_code;
- op0 = TREE_OPERAND (cond, 0);
- op1 = TREE_OPERAND (cond, 1);
- cond_code = TREE_CODE (cond);
+ op0 = gimple_cond_lhs (stmt);
+ op1 = gimple_cond_rhs (stmt);
+ cond_code = gimple_cond_code (stmt);
/* Get the current value of both operands. */
if (TREE_CODE (op0) == SSA_NAME)
{
- tree tmp = SSA_NAME_VALUE (op0);
- if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
- op0 = tmp;
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (op0) == SSA_NAME
+ && SSA_NAME_VALUE (op0))
+ op0 = SSA_NAME_VALUE (op0);
+ else
+ break;
+ }
}
if (TREE_CODE (op1) == SSA_NAME)
{
- tree tmp = SSA_NAME_VALUE (op1);
- if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
- op1 = tmp;
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (op1) == SSA_NAME
+ && SSA_NAME_VALUE (op1))
+ op1 = SSA_NAME_VALUE (op1);
+ else
+ break;
+ }
}
if (handle_dominating_asserts)
example, op0 might be a constant while op1 is an
SSA_NAME. Failure to canonicalize will cause us to
miss threading opportunities. */
- if (cond_code != SSA_NAME
- && tree_swap_operands_p (op0, op1, false))
+ if (tree_swap_operands_p (op0, op1, false))
{
- tree tmp;
- cond_code = swap_tree_comparison (TREE_CODE (cond));
- tmp = op0;
- op0 = op1;
- op1 = tmp;
+ cond_code = swap_tree_comparison (cond_code);
+ std::swap (op0, op1);
}
/* Stuff the operator and operands into our dummy conditional
expression. */
- TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
- TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
- TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
+ gimple_cond_set_code (dummy_cond, cond_code);
+ gimple_cond_set_lhs (dummy_cond, op0);
+ gimple_cond_set_rhs (dummy_cond, op1);
/* We absolutely do not care about any type conversions
we only care about a zero/nonzero value. */
fold_defer_overflow_warnings ();
- cached_lhs = fold (COND_EXPR_COND (dummy_cond));
- while (TREE_CODE (cached_lhs) == NOP_EXPR
- || TREE_CODE (cached_lhs) == CONVERT_EXPR
- || TREE_CODE (cached_lhs) == NON_LVALUE_EXPR)
- cached_lhs = TREE_OPERAND (cached_lhs, 0);
+ cached_lhs = fold_binary (cond_code, boolean_type_node, op0, op1);
+ if (cached_lhs)
+ while (CONVERT_EXPR_P (cached_lhs))
+ cached_lhs = TREE_OPERAND (cached_lhs, 0);
- fold_undefer_overflow_warnings (is_gimple_min_invariant (cached_lhs),
+ fold_undefer_overflow_warnings ((cached_lhs
+ && is_gimple_min_invariant (cached_lhs)),
stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
/* If we have not simplified the condition down to an invariant,
then use the pass specific callback to simplify the condition. */
- if (! is_gimple_min_invariant (cached_lhs))
- cached_lhs = (*simplify) (dummy_cond, stmt);
+ if (!cached_lhs
+ || !is_gimple_min_invariant (cached_lhs))
+ cached_lhs = (*simplify) (dummy_cond, stmt);
+
+ return cached_lhs;
}
+ if (code == GIMPLE_SWITCH)
+ cond = gimple_switch_index (as_a <gswitch *> (stmt));
+ else if (code == GIMPLE_GOTO)
+ cond = gimple_goto_dest (stmt);
+ else
+ gcc_unreachable ();
+
/* We can have conditionals which just test the state of a variable
rather than use a relational operator. These are simpler to handle. */
- else if (TREE_CODE (cond) == SSA_NAME)
+ if (TREE_CODE (cond) == SSA_NAME)
{
+ tree original_lhs = cond;
cached_lhs = cond;
- /* Get the variable's current value from the equivalency chains.
+ /* Get the variable's current value from the equivalence chains.
It is possible to get loops in the SSA_NAME_VALUE chains
(consider threading the backedge of a loop where we have
a loop invariant SSA_NAME used in the condition. */
- if (cached_lhs
- && TREE_CODE (cached_lhs) == SSA_NAME
- && SSA_NAME_VALUE (cached_lhs))
- cached_lhs = SSA_NAME_VALUE (cached_lhs);
+ if (cached_lhs)
+ {
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (cached_lhs) == SSA_NAME
+ && SSA_NAME_VALUE (cached_lhs))
+ cached_lhs = SSA_NAME_VALUE (cached_lhs);
+ else
+ break;
+ }
+ }
/* If we're dominated by a suitable ASSERT_EXPR, then
update CACHED_LHS appropriately. */
pass specific callback to try and simplify it further. */
if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
cached_lhs = (*simplify) (stmt, stmt);
+
+ /* We couldn't find an invariant. But, callers of this
+ function may be able to do something useful with the
+ unmodified destination. */
+ if (!cached_lhs)
+ cached_lhs = original_lhs;
}
else
cached_lhs = NULL;
return cached_lhs;
}
+/* Copy debug stmts from DEST's chain of single predecessors up to
+ SRC, so that we don't lose the bindings as PHI nodes are introduced
+ when DEST gains new predecessors. */
+void
+propagate_threaded_block_debug_into (basic_block dest, basic_block src)
+{
+ if (!MAY_HAVE_DEBUG_STMTS)
+ return;
+
+ if (!single_pred_p (dest))
+ return;
+
+ gcc_checking_assert (dest != src);
+
+ gimple_stmt_iterator gsi = gsi_after_labels (dest);
+ int i = 0;
+ const int alloc_count = 16; // ?? Should this be a PARAM?
+
+ /* Estimate the number of debug vars overridden in the beginning of
+ DEST, to tell how many we're going to need to begin with. */
+ for (gimple_stmt_iterator si = gsi;
+ i * 4 <= alloc_count * 3 && !gsi_end_p (si); gsi_next (&si))
+ {
+ gimple stmt = gsi_stmt (si);
+ if (!is_gimple_debug (stmt))
+ break;
+ i++;
+ }
+
+ auto_vec<tree, alloc_count> fewvars;
+ hash_set<tree> *vars = NULL;
+
+ /* If we're already starting with 3/4 of alloc_count, go for a
+ hash_set, otherwise start with an unordered stack-allocated
+ VEC. */
+ if (i * 4 > alloc_count * 3)
+ vars = new hash_set<tree>;
+
+ /* Now go through the initial debug stmts in DEST again, this time
+ actually inserting in VARS or FEWVARS. Don't bother checking for
+ duplicates in FEWVARS. */
+ for (gimple_stmt_iterator si = gsi; !gsi_end_p (si); gsi_next (&si))
+ {
+ gimple stmt = gsi_stmt (si);
+ if (!is_gimple_debug (stmt))
+ break;
+
+ tree var;
+
+ if (gimple_debug_bind_p (stmt))
+ var = gimple_debug_bind_get_var (stmt);
+ else if (gimple_debug_source_bind_p (stmt))
+ var = gimple_debug_source_bind_get_var (stmt);
+ else
+ gcc_unreachable ();
+
+ if (vars)
+ vars->add (var);
+ else
+ fewvars.quick_push (var);
+ }
+
+ basic_block bb = dest;
+
+ do
+ {
+ bb = single_pred (bb);
+ for (gimple_stmt_iterator si = gsi_last_bb (bb);
+ !gsi_end_p (si); gsi_prev (&si))
+ {
+ gimple stmt = gsi_stmt (si);
+ if (!is_gimple_debug (stmt))
+ continue;
+
+ tree var;
+
+ if (gimple_debug_bind_p (stmt))
+ var = gimple_debug_bind_get_var (stmt);
+ else if (gimple_debug_source_bind_p (stmt))
+ var = gimple_debug_source_bind_get_var (stmt);
+ else
+ gcc_unreachable ();
+
+ /* Discard debug bind overlaps. ??? Unlike stmts from src,
+ copied into a new block that will precede BB, debug bind
+ stmts in bypassed BBs may actually be discarded if
+ they're overwritten by subsequent debug bind stmts, which
+ might be a problem once we introduce stmt frontier notes
+ or somesuch. Adding `&& bb == src' to the condition
+ below will preserve all potentially relevant debug
+ notes. */
+ if (vars && vars->add (var))
+ continue;
+ else if (!vars)
+ {
+ int i = fewvars.length ();
+ while (i--)
+ if (fewvars[i] == var)
+ break;
+ if (i >= 0)
+ continue;
+
+ if (fewvars.length () < (unsigned) alloc_count)
+ fewvars.quick_push (var);
+ else
+ {
+ vars = new hash_set<tree>;
+ for (i = 0; i < alloc_count; i++)
+ vars->add (fewvars[i]);
+ fewvars.release ();
+ vars->add (var);
+ }
+ }
+
+ stmt = gimple_copy (stmt);
+ /* ??? Should we drop the location of the copy to denote
+ they're artificial bindings? */
+ gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
+ }
+ }
+ while (bb != src && single_pred_p (bb));
+
+ if (vars)
+ delete vars;
+ else if (fewvars.exists ())
+ fewvars.release ();
+}
+
+/* See if TAKEN_EDGE->dest is a threadable block with no side effecs (ie, it
+ need not be duplicated as part of the CFG/SSA updating process).
+
+ If it is threadable, add it to PATH and VISITED and recurse, ultimately
+ returning TRUE from the toplevel call. Otherwise do nothing and
+ return false.
+
+ DUMMY_COND, HANDLE_DOMINATING_ASSERTS and SIMPLIFY are used to
+ try and simplify the condition at the end of TAKEN_EDGE->dest. */
+static bool
+thread_around_empty_blocks (edge taken_edge,
+ gcond *dummy_cond,
+ bool handle_dominating_asserts,
+ tree (*simplify) (gimple, gimple),
+ bitmap visited,
+ vec<jump_thread_edge *> *path,
+ bool *backedge_seen_p)
+{
+ basic_block bb = taken_edge->dest;
+ gimple_stmt_iterator gsi;
+ gimple stmt;
+ tree cond;
+
+ /* The key property of these blocks is that they need not be duplicated
+ when threading. Thus they can not have visible side effects such
+ as PHI nodes. */
+ if (!gsi_end_p (gsi_start_phis (bb)))
+ return false;
+
+ /* Skip over DEBUG statements at the start of the block. */
+ gsi = gsi_start_nondebug_bb (bb);
+
+ /* If the block has no statements, but does have a single successor, then
+ it's just a forwarding block and we can thread through it trivially.
+
+ However, note that just threading through empty blocks with single
+ successors is not inherently profitable. For the jump thread to
+ be profitable, we must avoid a runtime conditional.
+
+ By taking the return value from the recursive call, we get the
+ desired effect of returning TRUE when we found a profitable jump
+ threading opportunity and FALSE otherwise.
+
+ This is particularly important when this routine is called after
+ processing a joiner block. Returning TRUE too aggressively in
+ that case results in pointless duplication of the joiner block. */
+ if (gsi_end_p (gsi))
+ {
+ if (single_succ_p (bb))
+ {
+ taken_edge = single_succ_edge (bb);
+ if (!bitmap_bit_p (visited, taken_edge->dest->index))
+ {
+ jump_thread_edge *x
+ = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
+ path->safe_push (x);
+ bitmap_set_bit (visited, taken_edge->dest->index);
+ *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+ return thread_around_empty_blocks (taken_edge,
+ dummy_cond,
+ handle_dominating_asserts,
+ simplify,
+ visited,
+ path,
+ backedge_seen_p);
+ }
+ }
+
+ /* We have a block with no statements, but multiple successors? */
+ return false;
+ }
+
+ /* The only real statements this block can have are a control
+ flow altering statement. Anything else stops the thread. */
+ stmt = gsi_stmt (gsi);
+ if (gimple_code (stmt) != GIMPLE_COND
+ && gimple_code (stmt) != GIMPLE_GOTO
+ && gimple_code (stmt) != GIMPLE_SWITCH)
+ return false;
+
+ /* If we have traversed a backedge, then we do not want to look
+ at certain expressions in the table that can not be relied upon.
+ Luckily the only code that looked at those expressions is the
+ SIMPLIFY callback, which we replace if we can no longer use it. */
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+
+ /* Extract and simplify the condition. */
+ cond = simplify_control_stmt_condition (taken_edge, stmt, dummy_cond,
+ simplify, handle_dominating_asserts);
+
+ /* If the condition can be statically computed and we have not already
+ visited the destination edge, then add the taken edge to our thread
+ path. */
+ if (cond && is_gimple_min_invariant (cond))
+ {
+ taken_edge = find_taken_edge (bb, cond);
+
+ if (bitmap_bit_p (visited, taken_edge->dest->index))
+ return false;
+ bitmap_set_bit (visited, taken_edge->dest->index);
+
+ jump_thread_edge *x
+ = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
+ path->safe_push (x);
+ *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+
+ thread_around_empty_blocks (taken_edge,
+ dummy_cond,
+ handle_dominating_asserts,
+ simplify,
+ visited,
+ path,
+ backedge_seen_p);
+ return true;
+ }
+
+ return false;
+}
+
+/* Return true if the CFG contains at least one path from START_BB to END_BB.
+ When a path is found, record in PATH the blocks from END_BB to START_BB.
+ VISITED_BBS is used to make sure we don't fall into an infinite loop. Bound
+ the recursion to basic blocks belonging to LOOP. */
+
+static bool
+fsm_find_thread_path (basic_block start_bb, basic_block end_bb,
+ vec<basic_block, va_gc> *&path,
+ hash_set<basic_block> *visited_bbs, loop_p loop)
+{
+ if (loop != start_bb->loop_father)
+ return false;
+
+ if (start_bb == end_bb)
+ {
+ vec_safe_push (path, start_bb);
+ return true;
+ }
+
+ if (!visited_bbs->add (start_bb))
+ {
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, start_bb->succs)
+ if (fsm_find_thread_path (e->dest, end_bb, path, visited_bbs, loop))
+ {
+ vec_safe_push (path, start_bb);
+ return true;
+ }
+ }
+
+ return false;
+}
+
+static int max_threaded_paths;
+
+/* We trace the value of the variable EXPR back through any phi nodes looking
+ for places where it gets a constant value and save the path. Stop after
+ having recorded MAX_PATHS jump threading paths. */
+
+static void
+fsm_find_control_statement_thread_paths (tree expr,
+ hash_set<basic_block> *visited_bbs,
+ vec<basic_block, va_gc> *&path,
+ bool seen_loop_phi)
+{
+ tree var = SSA_NAME_VAR (expr);
+ gimple def_stmt = SSA_NAME_DEF_STMT (expr);
+ basic_block var_bb = gimple_bb (def_stmt);
+
+ if (var == NULL || var_bb == NULL)
+ return;
+
+ /* For the moment we assume that an SSA chain only contains phi nodes, and
+ eventually one of the phi arguments will be an integer constant. In the
+ future, this could be extended to also handle simple assignments of
+ arithmetic operations. */
+ if (gimple_code (def_stmt) != GIMPLE_PHI)
+ return;
+
+ /* Avoid infinite recursion. */
+ if (visited_bbs->add (var_bb))
+ return;
+
+ gphi *phi = as_a <gphi *> (def_stmt);
+ int next_path_length = 0;
+ basic_block last_bb_in_path = path->last ();
+
+ if (loop_containing_stmt (phi)->header == gimple_bb (phi))
+ {
+ /* Do not walk through more than one loop PHI node. */
+ if (seen_loop_phi)
+ return;
+ seen_loop_phi = true;
+ }
+
+ /* Following the chain of SSA_NAME definitions, we jumped from a definition in
+ LAST_BB_IN_PATH to a definition in VAR_BB. When these basic blocks are
+ different, append to PATH the blocks from LAST_BB_IN_PATH to VAR_BB. */
+ if (var_bb != last_bb_in_path)
+ {
+ edge e;
+ int e_count = 0;
+ edge_iterator ei;
+ vec<basic_block, va_gc> *next_path;
+ vec_alloc (next_path, n_basic_blocks_for_fn (cfun));
+
+ FOR_EACH_EDGE (e, ei, last_bb_in_path->preds)
+ {
+ hash_set<basic_block> *visited_bbs = new hash_set<basic_block>;
+
+ if (fsm_find_thread_path (var_bb, e->src, next_path, visited_bbs,
+ e->src->loop_father))
+ ++e_count;
+
+ delete visited_bbs;
+
+ /* If there is more than one path, stop. */
+ if (e_count > 1)
+ {
+ vec_free (next_path);
+ return;
+ }
+ }
+
+ /* Stop if we have not found a path: this could occur when the recursion
+ is stopped by one of the bounds. */
+ if (e_count == 0)
+ {
+ vec_free (next_path);
+ return;
+ }
+
+ /* Append all the nodes from NEXT_PATH to PATH. */
+ vec_safe_splice (path, next_path);
+ next_path_length = next_path->length ();
+ vec_free (next_path);
+ }
+
+ gcc_assert (path->last () == var_bb);
+
+ /* Iterate over the arguments of PHI. */
+ unsigned int i;
+ for (i = 0; i < gimple_phi_num_args (phi); i++)
+ {
+ tree arg = gimple_phi_arg_def (phi, i);
+ basic_block bbi = gimple_phi_arg_edge (phi, i)->src;
+
+ /* Skip edges pointing outside the current loop. */
+ if (!arg || var_bb->loop_father != bbi->loop_father)
+ continue;
+
+ if (TREE_CODE (arg) == SSA_NAME)
+ {
+ vec_safe_push (path, bbi);
+ /* Recursively follow SSA_NAMEs looking for a constant definition. */
+ fsm_find_control_statement_thread_paths (arg, visited_bbs, path,
+ seen_loop_phi);
+
+ path->pop ();
+ continue;
+ }
+
+ if (TREE_CODE (arg) != INTEGER_CST)
+ continue;
+
+ int path_length = path->length ();
+ /* A path with less than 2 basic blocks should not be jump-threaded. */
+ if (path_length < 2)
+ continue;
+
+ if (path_length > PARAM_VALUE (PARAM_MAX_FSM_THREAD_LENGTH))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the number of basic blocks on the path "
+ "exceeds PARAM_MAX_FSM_THREAD_LENGTH.\n");
+ continue;
+ }
+
+ if (max_threaded_paths <= 0)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the number of previously recorded FSM paths to thread "
+ "exceeds PARAM_MAX_FSM_THREAD_PATHS.\n");
+ continue;
+ }
+
+ /* Add BBI to the path. */
+ vec_safe_push (path, bbi);
+ ++path_length;
+
+ int n_insns = 0;
+ gimple_stmt_iterator gsi;
+ int j;
+ loop_p loop = (*path)[0]->loop_father;
+ bool path_crosses_loops = false;
+
+ /* Count the number of instructions on the path: as these instructions
+ will have to be duplicated, we will not record the path if there are
+ too many instructions on the path. Also check that all the blocks in
+ the path belong to a single loop. */
+ for (j = 1; j < path_length - 1; j++)
+ {
+ basic_block bb = (*path)[j];
+
+ if (bb->loop_father != loop)
+ {
+ path_crosses_loops = true;
+ break;
+ }
+
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple stmt = gsi_stmt (gsi);
+ /* Do not count empty statements and labels. */
+ if (gimple_code (stmt) != GIMPLE_NOP
+ && gimple_code (stmt) != GIMPLE_LABEL
+ && !is_gimple_debug (stmt))
+ ++n_insns;
+ }
+ }
+
+ if (path_crosses_loops)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the path crosses loops.\n");
+ path->pop ();
+ continue;
+ }
+
+ if (n_insns >= PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATH_INSNS))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the number of instructions on the path "
+ "exceeds PARAM_MAX_FSM_THREAD_PATH_INSNS.\n");
+ path->pop ();
+ continue;
+ }
+
+ vec<jump_thread_edge *> *jump_thread_path
+ = new vec<jump_thread_edge *> ();
+
+ /* Record the edges between the blocks in PATH. */
+ for (j = 0; j < path_length - 1; j++)
+ {
+ edge e = find_edge ((*path)[path_length - j - 1],
+ (*path)[path_length - j - 2]);
+ gcc_assert (e);
+ jump_thread_edge *x = new jump_thread_edge (e, EDGE_FSM_THREAD);
+ jump_thread_path->safe_push (x);
+ }
+
+ /* Add the edge taken when the control variable has value ARG. */
+ edge taken_edge = find_taken_edge ((*path)[0], arg);
+ jump_thread_edge *x
+ = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
+ jump_thread_path->safe_push (x);
+
+ register_jump_thread (jump_thread_path);
+ --max_threaded_paths;
+
+ /* Remove BBI from the path. */
+ path->pop ();
+ }
+
+ /* Remove all the nodes that we added from NEXT_PATH. */
+ if (next_path_length)
+ vec_safe_truncate (path, (path->length () - next_path_length));
+}
+
/* We are exiting E->src, see if E->dest ends with a conditional
- jump which has a known value when reached via E.
+ jump which has a known value when reached via E.
+
+ E->dest can have arbitrary side effects which, if threading is
+ successful, will be maintained.
Special care is necessary if E is a back edge in the CFG as we
may have already recorded equivalences for E->dest into our
limited in that case to avoid short-circuiting the loop
incorrectly.
- Note it is quite common for the first block inside a loop to
- end with a conditional which is either always true or always
- false when reached via the loop backedge. Thus we do not want
- to blindly disable threading across a loop backedge. */
+ DUMMY_COND is a shared cond_expr used by condition simplification as scratch,
+ to avoid allocating memory.
-void
-thread_across_edge (tree dummy_cond,
- edge e,
- bool handle_dominating_asserts,
- VEC(tree, heap) **stack,
- tree (*simplify) (tree, tree))
-{
- tree stmt;
+ HANDLE_DOMINATING_ASSERTS is true if we should try to replace operands of
+ the simplified condition with left-hand sides of ASSERT_EXPRs they are
+ used in.
- /* If E is a backedge, then we want to verify that the COND_EXPR,
- SWITCH_EXPR or GOTO_EXPR at the end of e->dest is not affected
- by any statements in e->dest. If it is affected, then it is not
- safe to thread this edge. */
- if (e->flags & EDGE_DFS_BACK)
- {
- ssa_op_iter iter;
- use_operand_p use_p;
- tree last = bsi_stmt (bsi_last (e->dest));
+ STACK is used to undo temporary equivalences created during the walk of
+ E->dest.
- FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE)
- {
- tree use = USE_FROM_PTR (use_p);
+ SIMPLIFY is a pass-specific function used to simplify statements.
- if (TREE_CODE (use) == SSA_NAME
- && TREE_CODE (SSA_NAME_DEF_STMT (use)) != PHI_NODE
- && bb_for_stmt (SSA_NAME_DEF_STMT (use)) == e->dest)
- goto fail;
- }
- }
-
- stmt_count = 0;
+ Our caller is responsible for restoring the state of the expression
+ and const_and_copies stacks.
- /* PHIs create temporary equivalences. */
- if (!record_temporary_equivalences_from_phis (e, stack))
- goto fail;
+ Positive return value is success. Zero return value is failure, but
+ the block can still be duplicated as a joiner in a jump thread path,
+ negative indicates the block should not be duplicated and thus is not
+ suitable for a joiner in a jump threading path. */
+
+static int
+thread_through_normal_block (edge e,
+ gcond *dummy_cond,
+ bool handle_dominating_asserts,
+ const_and_copies *const_and_copies,
+ tree (*simplify) (gimple, gimple),
+ vec<jump_thread_edge *> *path,
+ bitmap visited,
+ bool *backedge_seen_p)
+{
+ /* If we have traversed a backedge, then we do not want to look
+ at certain expressions in the table that can not be relied upon.
+ Luckily the only code that looked at those expressions is the
+ SIMPLIFY callback, which we replace if we can no longer use it. */
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+
+ /* PHIs create temporary equivalences.
+ Note that if we found a PHI that made the block non-threadable, then
+ we need to bubble that up to our caller in the same manner we do
+ when we prematurely stop processing statements below. */
+ if (!record_temporary_equivalences_from_phis (e, const_and_copies))
+ return -1;
/* Now walk each statement recording any context sensitive
temporary equivalences we can detect. */
- stmt = record_temporary_equivalences_from_stmts_at_dest (e, stack, simplify);
+ gimple stmt
+ = record_temporary_equivalences_from_stmts_at_dest (e, const_and_copies, simplify,
+ *backedge_seen_p);
+
+ /* There's two reasons STMT might be null, and distinguishing
+ between them is important.
+
+ First the block may not have had any statements. For example, it
+ might have some PHIs and unconditionally transfer control elsewhere.
+ Such blocks are suitable for jump threading, particularly as a
+ joiner block.
+
+ The second reason would be if we did not process all the statements
+ in the block (because there were too many to make duplicating the
+ block profitable. If we did not look at all the statements, then
+ we may not have invalidated everything needing invalidation. Thus
+ we must signal to our caller that this block is not suitable for
+ use as a joiner in a threading path. */
if (!stmt)
- goto fail;
-
+ {
+ /* First case. The statement simply doesn't have any instructions, but
+ does have PHIs. */
+ if (gsi_end_p (gsi_start_nondebug_bb (e->dest))
+ && !gsi_end_p (gsi_start_phis (e->dest)))
+ return 0;
+
+ /* Second case. */
+ return -1;
+ }
+
/* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
will be taken. */
- if (TREE_CODE (stmt) == COND_EXPR
- || TREE_CODE (stmt) == GOTO_EXPR
- || TREE_CODE (stmt) == SWITCH_EXPR)
+ if (gimple_code (stmt) == GIMPLE_COND
+ || gimple_code (stmt) == GIMPLE_GOTO
+ || gimple_code (stmt) == GIMPLE_SWITCH)
{
tree cond;
/* Extract and simplify the condition. */
- cond = simplify_control_stmt_condition (e, stmt, dummy_cond, simplify, handle_dominating_asserts);
+ cond = simplify_control_stmt_condition (e, stmt, dummy_cond, simplify,
+ handle_dominating_asserts);
- if (cond && is_gimple_min_invariant (cond))
+ if (!cond)
+ return 0;
+
+ if (is_gimple_min_invariant (cond))
{
edge taken_edge = find_taken_edge (e->dest, cond);
basic_block dest = (taken_edge ? taken_edge->dest : NULL);
- if (dest == e->dest)
- goto fail;
+ /* DEST could be NULL for a computed jump to an absolute
+ address. */
+ if (dest == NULL
+ || dest == e->dest
+ || bitmap_bit_p (visited, dest->index))
+ return 0;
+
+ /* Only push the EDGE_START_JUMP_THREAD marker if this is
+ first edge on the path. */
+ if (path->length () == 0)
+ {
+ jump_thread_edge *x
+ = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
+ path->safe_push (x);
+ *backedge_seen_p |= ((e->flags & EDGE_DFS_BACK) != 0);
+ }
+
+ jump_thread_edge *x
+ = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_BLOCK);
+ path->safe_push (x);
+ *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+
+ /* See if we can thread through DEST as well, this helps capture
+ secondary effects of threading without having to re-run DOM or
+ VRP.
+
+ We don't want to thread back to a block we have already
+ visited. This may be overly conservative. */
+ bitmap_set_bit (visited, dest->index);
+ bitmap_set_bit (visited, e->dest->index);
+ thread_around_empty_blocks (taken_edge,
+ dummy_cond,
+ handle_dominating_asserts,
+ simplify,
+ visited,
+ path,
+ backedge_seen_p);
+ return 1;
+ }
+
+ if (!flag_expensive_optimizations
+ || optimize_function_for_size_p (cfun)
+ || TREE_CODE (cond) != SSA_NAME
+ || e->dest->loop_father != e->src->loop_father
+ || loop_depth (e->dest->loop_father) == 0)
+ return 0;
+
+ /* When COND cannot be simplified, try to find paths from a control
+ statement back through the PHI nodes which would affect that control
+ statement. */
+ vec<basic_block, va_gc> *bb_path;
+ vec_alloc (bb_path, n_basic_blocks_for_fn (cfun));
+ vec_safe_push (bb_path, e->dest);
+ hash_set<basic_block> *visited_bbs = new hash_set<basic_block>;
+
+ max_threaded_paths = PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATHS);
+ fsm_find_control_statement_thread_paths (cond, visited_bbs, bb_path,
+ false);
+
+ delete visited_bbs;
+ vec_free (bb_path);
+ }
+ return 0;
+}
+
+/* We are exiting E->src, see if E->dest ends with a conditional
+ jump which has a known value when reached via E.
+
+ Special care is necessary if E is a back edge in the CFG as we
+ may have already recorded equivalences for E->dest into our
+ various tables, including the result of the conditional at
+ the end of E->dest. Threading opportunities are severely
+ limited in that case to avoid short-circuiting the loop
+ incorrectly.
+
+ Note it is quite common for the first block inside a loop to
+ end with a conditional which is either always true or always
+ false when reached via the loop backedge. Thus we do not want
+ to blindly disable threading across a loop backedge.
+
+ DUMMY_COND is a shared cond_expr used by condition simplification as scratch,
+ to avoid allocating memory.
- remove_temporary_equivalences (stack);
- register_jump_thread (e, taken_edge);
+ HANDLE_DOMINATING_ASSERTS is true if we should try to replace operands of
+ the simplified condition with left-hand sides of ASSERT_EXPRs they are
+ used in.
+
+ STACK is used to undo temporary equivalences created during the walk of
+ E->dest.
+
+ SIMPLIFY is a pass-specific function used to simplify statements. */
+
+void
+thread_across_edge (gcond *dummy_cond,
+ edge e,
+ bool handle_dominating_asserts,
+ const_and_copies *const_and_copies,
+ tree (*simplify) (gimple, gimple))
+{
+ bitmap visited = BITMAP_ALLOC (NULL);
+ bool backedge_seen;
+
+ stmt_count = 0;
+
+ vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> ();
+ bitmap_clear (visited);
+ bitmap_set_bit (visited, e->src->index);
+ bitmap_set_bit (visited, e->dest->index);
+ backedge_seen = ((e->flags & EDGE_DFS_BACK) != 0);
+ if (backedge_seen)
+ simplify = dummy_simplify;
+
+ int threaded = thread_through_normal_block (e, dummy_cond,
+ handle_dominating_asserts,
+ const_and_copies, simplify, path,
+ visited, &backedge_seen);
+ if (threaded > 0)
+ {
+ propagate_threaded_block_debug_into (path->last ()->e->dest,
+ e->dest);
+ const_and_copies->pop_to_marker ();
+ BITMAP_FREE (visited);
+ register_jump_thread (path);
+ return;
+ }
+ else
+ {
+ /* Negative and zero return values indicate no threading was possible,
+ thus there should be no edges on the thread path and no need to walk
+ through the vector entries. */
+ gcc_assert (path->length () == 0);
+ path->release ();
+ delete path;
+
+ /* A negative status indicates the target block was deemed too big to
+ duplicate. Just quit now rather than trying to use the block as
+ a joiner in a jump threading path.
+
+ This prevents unnecessary code growth, but more importantly if we
+ do not look at all the statements in the block, then we may have
+ missed some invalidations if we had traversed a backedge! */
+ if (threaded < 0)
+ {
+ BITMAP_FREE (visited);
+ const_and_copies->pop_to_marker ();
+ return;
}
}
- fail:
- remove_temporary_equivalences (stack);
+ /* We were unable to determine what out edge from E->dest is taken. However,
+ we might still be able to thread through successors of E->dest. This
+ often occurs when E->dest is a joiner block which then fans back out
+ based on redundant tests.
+
+ If so, we'll copy E->dest and redirect the appropriate predecessor to
+ the copy. Within the copy of E->dest, we'll thread one or more edges
+ to points deeper in the CFG.
+
+ This is a stopgap until we have a more structured approach to path
+ isolation. */
+ {
+ edge taken_edge;
+ edge_iterator ei;
+ bool found;
+
+ /* If E->dest has abnormal outgoing edges, then there's no guarantee
+ we can safely redirect any of the edges. Just punt those cases. */
+ FOR_EACH_EDGE (taken_edge, ei, e->dest->succs)
+ if (taken_edge->flags & EDGE_ABNORMAL)
+ {
+ const_and_copies->pop_to_marker ();
+ BITMAP_FREE (visited);
+ return;
+ }
+
+ /* Look at each successor of E->dest to see if we can thread through it. */
+ FOR_EACH_EDGE (taken_edge, ei, e->dest->succs)
+ {
+ /* Push a fresh marker so we can unwind the equivalences created
+ for each of E->dest's successors. */
+ const_and_copies->push_marker ();
+
+ /* Avoid threading to any block we have already visited. */
+ bitmap_clear (visited);
+ bitmap_set_bit (visited, e->src->index);
+ bitmap_set_bit (visited, e->dest->index);
+ bitmap_set_bit (visited, taken_edge->dest->index);
+ vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> ();
+
+ /* Record whether or not we were able to thread through a successor
+ of E->dest. */
+ jump_thread_edge *x = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
+ path->safe_push (x);
+
+ x = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_JOINER_BLOCK);
+ path->safe_push (x);
+ found = false;
+ backedge_seen = ((e->flags & EDGE_DFS_BACK) != 0);
+ backedge_seen |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (backedge_seen)
+ simplify = dummy_simplify;
+ found = thread_around_empty_blocks (taken_edge,
+ dummy_cond,
+ handle_dominating_asserts,
+ simplify,
+ visited,
+ path,
+ &backedge_seen);
+
+ if (backedge_seen)
+ simplify = dummy_simplify;
+
+ if (!found)
+ found = thread_through_normal_block (path->last ()->e, dummy_cond,
+ handle_dominating_asserts,
+ const_and_copies, simplify, path, visited,
+ &backedge_seen) > 0;
+
+ /* If we were able to thread through a successor of E->dest, then
+ record the jump threading opportunity. */
+ if (found)
+ {
+ propagate_threaded_block_debug_into (path->last ()->e->dest,
+ taken_edge->dest);
+ register_jump_thread (path);
+ }
+ else
+ {
+ delete_jump_thread_path (path);
+ }
+
+ /* And unwind the equivalence table. */
+ const_and_copies->pop_to_marker ();
+ }
+ BITMAP_FREE (visited);
+ }
+
+ const_and_copies->pop_to_marker ();
}