/* Optimization of PHI nodes by converting them into straightline code.
- Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
- Inc.
+ Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010
+ Free Software Foundation, Inc.
This file is part of GCC.
edge, edge, gimple, tree, tree);
static bool cond_store_replacement (basic_block, basic_block, edge, edge,
struct pointer_set_t *);
+static bool cond_if_else_store_replacement (basic_block, basic_block, basic_block);
static struct pointer_set_t * get_non_trapping (void);
static void replace_phi_edge_with_variable (basic_block, edge, gimple, tree);
bb0:
if (cond) goto bb2; else goto bb1;
bb1:
- *p = RHS
+ *p = RHS;
bb2:
with
condtmp' = *p;
bb2:
condtmp = PHI <RHS, condtmp'>
- *p = condtmp
+ *p = condtmp;
This transformation can only be done under several constraints,
- documented below. */
+ documented below. It also replaces:
+
+ bb0:
+ if (cond) goto bb2; else goto bb1;
+ bb1:
+ *p = RHS1;
+ goto bb3;
+ bb2:
+ *p = RHS2;
+ bb3:
+
+ with
+
+ bb0:
+ if (cond) goto bb3; else goto bb1;
+ bb1:
+ bb3:
+ condtmp = PHI <RHS1, RHS2>
+ *p = condtmp; */
static unsigned int
tree_ssa_cs_elim (void)
e1 = e2;
e2 = e_tmp;
}
+ else if (do_store_elim
+ && EDGE_SUCC (bb1, 0)->dest == EDGE_SUCC (bb2, 0)->dest)
+ {
+ basic_block bb3 = EDGE_SUCC (bb1, 0)->dest;
+
+ if (!single_succ_p (bb1)
+ || (EDGE_SUCC (bb1, 0)->flags & EDGE_FALLTHRU) == 0
+ || !single_succ_p (bb2)
+ || (EDGE_SUCC (bb2, 0)->flags & EDGE_FALLTHRU) == 0
+ || EDGE_COUNT (bb3->preds) != 2)
+ continue;
+ if (cond_if_else_store_replacement (bb1, bb2, bb3))
+ cfgchanged = true;
+ continue;
+ }
else
- continue;
+ continue;
e1 = EDGE_SUCC (bb1, 0);
gimple newphi, new_stmt;
gimple_stmt_iterator gsi;
source_location locus;
- enum tree_code code;
/* Check if middle_bb contains of only one store. */
if (!assign
- || gimple_code (assign) != GIMPLE_ASSIGN)
+ || !gimple_assign_single_p (assign))
return false;
locus = gimple_location (assign);
lhs = gimple_assign_lhs (assign);
rhs = gimple_assign_rhs1 (assign);
if (TREE_CODE (lhs) != MEM_REF
- || TREE_CODE (TREE_OPERAND (lhs, 0)) != SSA_NAME)
+ || TREE_CODE (TREE_OPERAND (lhs, 0)) != SSA_NAME
+ || !is_gimple_reg_type (TREE_TYPE (lhs)))
return false;
- /* RHS is either a single SSA_NAME or a constant. */
- code = gimple_assign_rhs_code (assign);
- if (get_gimple_rhs_class (code) != GIMPLE_SINGLE_RHS
- || (code != SSA_NAME && !is_gimple_min_invariant (rhs)))
- return false;
/* Prove that we can move the store down. We could also check
TREE_THIS_NOTRAP here, but in that case we also could move stores,
whose value is not available readily, which we want to avoid. */
/* Now we've checked the constraints, so do the transformation:
1) Remove the single store. */
- mark_symbols_for_renaming (assign);
gsi = gsi_for_stmt (assign);
+ unlink_stmt_vdef (assign);
gsi_remove (&gsi, true);
+ release_defs (assign);
/* 2) Create a temporary where we can store the old content
of the memory touched by the store, if we need to. */
name = make_ssa_name (condstoretemp, new_stmt);
gimple_assign_set_lhs (new_stmt, name);
gimple_set_location (new_stmt, locus);
- mark_symbols_for_renaming (new_stmt);
gsi_insert_on_edge (e1, new_stmt);
/* 4) Create a PHI node at the join block, with one argument
lhs = unshare_expr (lhs);
new_stmt = gimple_build_assign (lhs, PHI_RESULT (newphi));
- mark_symbols_for_renaming (new_stmt);
/* 5) Insert that PHI node. */
gsi = gsi_after_labels (join_bb);
return true;
}
+/* Do the main work of conditional store replacement. We already know
+ that the recognized pattern looks like so:
+
+ split:
+ if (cond) goto THEN_BB; else goto ELSE_BB (edge E1)
+ THEN_BB:
+ X = Y;
+ goto JOIN_BB;
+ ELSE_BB:
+ X = Z;
+ fallthrough (edge E0)
+ JOIN_BB:
+ some more
+
+ We check that THEN_BB and ELSE_BB contain only one store
+ that the stores have a "simple" RHS. */
+
+static bool
+cond_if_else_store_replacement (basic_block then_bb, basic_block else_bb,
+ basic_block join_bb)
+{
+ gimple then_assign = last_and_only_stmt (then_bb);
+ gimple else_assign = last_and_only_stmt (else_bb);
+ tree lhs_base, lhs, then_rhs, else_rhs;
+ source_location then_locus, else_locus;
+ gimple_stmt_iterator gsi;
+ gimple newphi, new_stmt;
+
+ /* Check if then_bb and else_bb contain only one store each. */
+ if (then_assign == NULL
+ || !gimple_assign_single_p (then_assign)
+ || else_assign == NULL
+ || !gimple_assign_single_p (else_assign))
+ return false;
+
+ lhs = gimple_assign_lhs (then_assign);
+ if (!is_gimple_reg_type (TREE_TYPE (lhs))
+ || !operand_equal_p (lhs, gimple_assign_lhs (else_assign), 0))
+ return false;
+
+ lhs_base = get_base_address (lhs);
+ if (lhs_base == NULL_TREE
+ || (!DECL_P (lhs_base) && TREE_CODE (lhs_base) != MEM_REF))
+ return false;
+
+ then_rhs = gimple_assign_rhs1 (then_assign);
+ else_rhs = gimple_assign_rhs1 (else_assign);
+ then_locus = gimple_location (then_assign);
+ else_locus = gimple_location (else_assign);
+
+ /* Now we've checked the constraints, so do the transformation:
+ 1) Remove the stores. */
+ gsi = gsi_for_stmt (then_assign);
+ unlink_stmt_vdef (then_assign);
+ gsi_remove (&gsi, true);
+ release_defs (then_assign);
+
+ gsi = gsi_for_stmt (else_assign);
+ unlink_stmt_vdef (else_assign);
+ gsi_remove (&gsi, true);
+ release_defs (else_assign);
+
+ /* 2) Create a temporary where we can store the old content
+ of the memory touched by the store, if we need to. */
+ if (!condstoretemp || TREE_TYPE (lhs) != TREE_TYPE (condstoretemp))
+ {
+ condstoretemp = create_tmp_reg (TREE_TYPE (lhs), "cstore");
+ get_var_ann (condstoretemp);
+ }
+ add_referenced_var (condstoretemp);
+
+ /* 3) Create a PHI node at the join block, with one argument
+ holding the old RHS, and the other holding the temporary
+ where we stored the old memory contents. */
+ newphi = create_phi_node (condstoretemp, join_bb);
+ add_phi_arg (newphi, then_rhs, EDGE_SUCC (then_bb, 0), then_locus);
+ add_phi_arg (newphi, else_rhs, EDGE_SUCC (else_bb, 0), else_locus);
+
+ new_stmt = gimple_build_assign (lhs, PHI_RESULT (newphi));
+
+ /* 4) Insert that PHI node. */
+ gsi = gsi_after_labels (join_bb);
+ if (gsi_end_p (gsi))
+ {
+ gsi = gsi_last_bb (join_bb);
+ gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
+ }
+ else
+ gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
+
+ return true;
+}
+
/* Always do these optimizations if we have SSA
trees to work on. */
static bool
OSDN Git Service
