===================================================================
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+extern int global;
+
+int bar(int);
+
+void foo (int bound)
+{
+ int i, ret = 0;
+ for (i = 0; i <= bound; i++)
+ {
+ if (i != bound)
+ global += bar (i);
+ }
+}
+
+/* { dg-final { scan-tree-dump "loop iv compare heuristics"
"profile_estimate"} } */
+/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
===================================================================
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+extern int global;
+
+int bar(int);
+
+void foo (int bound)
+{
+ int i, ret = 0;
+ for (i = 0; i < 10; i++)
+ {
+ if (i < 5)
+ global += bar (i);
+ }
+}
+
+/* { dg-final { scan-tree-dump "loop iv compare heuristics"
"profile_estimate"} } */
+/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
===================================================================
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+extern int global;
+
+int bar(int);
+
+void foo (int bound)
+{
+ int i, ret = 0;
+ for (i = 0; i < bound; i++)
+ {
+ if (i > bound - 2)
+ global += bar (i);
+ }
+}
+
+/* { dg-final { scan-tree-dump "loop iv compare heuristics"
"profile_estimate"} } */
+/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
===================================================================
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+extern int global;
+
+int bar(int);
+
+void foo (int bound)
+{
+ int i, ret = 0;
+ for (i = 0; i < bound; i++)
+ {
+ if (i > bound * bound )
+ global += bar (i);
+ }
+}
+
+/* { dg-final { scan-tree-dump-not "loop iv compare heuristics"
"profile_estimate"} } */
+/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
===================================================================
@@ -946,6 +946,332 @@
}
}
+/* Check if T1 and T2 satisfy the IV_COMPARE condition.
+ Return the SSA_NAME if the condition satisfies, NULL otherwise.
+
+ T1 and T2 should be one of the following cases:
+ 1. T1 is SSA_NAME, T2 is NULL
+ 2. T1 is SSA_NAME, T2 is INTEGER_CST between [-4, 4]
+ 3. T2 is SSA_NAME, T1 is INTEGER_CST between [-4, 4] */
+
+static tree
+find_qualified_ssa_name (tree t1, tree t2)
+{
+ tree ret = NULL;
+ int value = 0;
+
+ if (!t1)
+ return NULL;
+ else if (TREE_CODE (t1) == SSA_NAME)
+ ret = t1;
+ else if (TREE_CODE (t1) == INTEGER_CST && host_integerp (t1, 0))
+ value = tree_low_cst (t1, 0);
+ else
+ return NULL;
+
+ if (!t2)
+ return ret;
+ else if (TREE_CODE (t2) == INTEGER_CST && host_integerp (t2, 0))
+ value = tree_low_cst (t2, 0);
+ else if (TREE_CODE (t2) == SSA_NAME)
+ {
+ if (ret)
+ return NULL;
+ else
+ ret = t2;
+ }
+
+ if (value <= 4 && value >= -4)
+ return ret;
+ else
+ return NULL;
+}
+
+/* Return the SSA_NAME in T or T's operands.
+ Return NULL if T does not satisfy IV_COMPARE condition. */
+
+static tree
+find_ssa_name_in_expr (tree t)
+{
+ if (TREE_CODE (t) == SSA_NAME)
+ return t;
+
+ if (!BINARY_CLASS_P (t))
+ return NULL;
+
+ switch (TREE_OPERAND_LENGTH (t))
+ {
+ case 1:
+ return find_qualified_ssa_name (TREE_OPERAND (t, 0), NULL);
+ case 2:
+ return find_qualified_ssa_name (TREE_OPERAND (t, 0),
+ TREE_OPERAND (t, 1));
+ default:
+ return NULL;
+ }
+}
+
+/* Check the compare STMT in LOOP. If it compares an induction
+ variable to a loop invariant, return true, and save
+ LOOP_INVARIANT, COMPARE_CODE and LOOP_STEP.
+ Otherwise return false and set LOOP_INVAIANT to NULL. */
+
+static bool
+is_comparison_with_loop_invariant_p (gimple stmt, struct loop *loop,
+ tree *loop_invariant,
+ enum tree_code *compare_code,
+ int *loop_step,
+ tree *loop_iv_base)
+{
+ tree op0, op1, bound, base;
+ affine_iv iv0, iv1;
+ enum tree_code code;
+ int step;
+
+ code = gimple_cond_code (stmt);
+ *loop_invariant = NULL;
+
+ switch (code)
+ {
+ case GT_EXPR:
+ case GE_EXPR:
+ case NE_EXPR:
+ case LT_EXPR:
+ case LE_EXPR:
+ case EQ_EXPR:
+ break;
+
+ default:
+ return false;
+ }
+
+ op0 = gimple_cond_lhs (stmt);
+ op1 = gimple_cond_rhs (stmt);
+
+ if ((TREE_CODE (op0) != SSA_NAME && TREE_CODE (op0) != INTEGER_CST)
+ || (TREE_CODE (op1) != SSA_NAME && TREE_CODE (op1) != INTEGER_CST))
+ return false;
+ if (!simple_iv (loop, loop_containing_stmt (stmt), op0, &iv0, true))
+ return false;
+ if (!simple_iv (loop, loop_containing_stmt (stmt), op1, &iv1, true))
+ return false;
+ if (TREE_CODE (iv0.step) != INTEGER_CST
+ || TREE_CODE (iv1.step) != INTEGER_CST)
+ return false;
+ if ((integer_zerop (iv0.step) && integer_zerop (iv1.step))
+ || (!integer_zerop (iv0.step) && !integer_zerop (iv1.step)))
+ return false;
+
+ if (integer_zerop (iv0.step))
+ {
+ if (code != NE_EXPR && code != EQ_EXPR)
+ code = invert_tree_comparison (code, false);
+ bound = iv0.base;
+ base = iv1.base;
+ if (host_integerp (iv1.step, 0))
+ step = tree_low_cst (iv1.step, 0);
+ else
+ return false;
+ }
+ else
+ {
+ bound = iv1.base;
+ base = iv0.base;
+ if (host_integerp (iv0.step, 0))
+ step = tree_low_cst (iv0.step, 0);
+ else
+ return false;
+ }
+
+ if (TREE_CODE (bound) != INTEGER_CST)
+ bound = find_ssa_name_in_expr (bound);
+ if (!bound)
+ return false;
+
+ *loop_invariant = bound;
+ *compare_code = code;
+ *loop_step = step;
+ *loop_iv_base = base;
+ return true;
+}
+
+/* Compare two SSA_NAMEs: returns TRUE if T1 and T2 reference
+ a similar variable. */
+
+static bool
+is_bound_expr_similar (tree t1, tree t2)
+{
+ gimple stmt;
+ tree ssa_name_1 = NULL;
+ tree ssa_name_2 = NULL;
+
+ gcc_assert (TREE_CODE (t1) == SSA_NAME || TREE_CODE (t1) == INTEGER_CST);
+ gcc_assert (TREE_CODE (t2) == SSA_NAME || TREE_CODE (t2) == INTEGER_CST);
+
+ if (t1 == t2)
+ return true;
+
+ if (TREE_CODE (t1) == INTEGER_CST && TREE_CODE (t2) == INTEGER_CST)
+ return true;
+ if (TREE_CODE (t1) == INTEGER_CST || TREE_CODE (t2) == INTEGER_CST)
+ return false;
+
+ /* Check to see if t1 is expressed/defined with t2. */
+ stmt = SSA_NAME_DEF_STMT (t1);
+ gcc_assert (stmt != NULL);
+ if (is_gimple_assign (stmt))
+ {
+ ssa_name_1 = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
+ if (ssa_name_1 && ssa_name_1 == t2)
+ return true;
+ }
+
+ /* Check to see if t2 is expressed/defined with t1. */
+ stmt = SSA_NAME_DEF_STMT (t2);
+ gcc_assert (stmt != NULL);
+ if (is_gimple_assign (stmt))
+ {
+ ssa_name_2 = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
+ if (ssa_name_2 && ssa_name_2 == t1)
+ return true;
+ }
+
+ /* Compare if t1 and t2's def_stmts are identical. */
+ if (ssa_name_2 != NULL && ssa_name_1 == ssa_name_2)
+ return true;
+ else
+ return false;
+}
+
+/* Predict branch probability of BB when BB contains a branch that compares
+ an induction variable in LOOP to LOOP_BOUND_VAR. The loop exit is
+ compared using LOOP_BOUND_CODE, with step of LOOP_BOUND_STEP.
+
+ E.g.
+ for (int i = 0; i < bound; i++) {
+ if (i < bound - 2)
+ computation_1();
+ else
+ computation_2();
+ }
+
+ In this loop, we will predict the branch inside the loop to be taken. */
+
+static void
+predict_iv_comparison (struct loop *loop, basic_block bb,
+ tree loop_bound_var,
+ enum tree_code loop_bound_code,
+ int loop_bound_step)
+{
+ gimple stmt;
+ tree compare_var, compare_base;
+ enum tree_code compare_code;
+ int compare_step;
+ edge then_edge;
+ edge_iterator ei;
+
+ if (predicted_by_p (bb, PRED_LOOP_ITERATIONS_GUESSED)
+ || predicted_by_p (bb, PRED_LOOP_ITERATIONS)
+ || predicted_by_p (bb, PRED_LOOP_EXIT))
+ return;
+
+ stmt = last_stmt (bb);
+ if (!stmt || gimple_code (stmt) != GIMPLE_COND)
+ return;
+ if (!is_comparison_with_loop_invariant_p (stmt, loop, &compare_var,
+ &compare_code,
+ &compare_step,
+ &compare_base))
+ return;
+
+ /* Find the taken edge. */
+ FOR_EACH_EDGE (then_edge, ei, bb->succs)
+ if (then_edge->flags & EDGE_TRUE_VALUE)
+ break;
+
+ /* When comparing an IV to a loop invariant, NE is more likely to be
+ taken while EQ is more likely to be not-taken. */
+ if (compare_code == NE_EXPR)
+ {
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ return;
+ }
+ else if (compare_code == EQ_EXPR)
+ {
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
+ return;
+ }
+
+ if (!is_bound_expr_similar (loop_bound_var, compare_var))
+ return;
+
+ /* If loop bound, base and compare bound are all constents, we can
+ calculate the probability directly. */
+ if (TREE_CODE (loop_bound_var) == INTEGER_CST
+ && TREE_CODE (compare_var) == INTEGER_CST
+ && TREE_CODE (compare_base) == INTEGER_CST
+ && host_integerp (loop_bound_var, 0)
+ && host_integerp (compare_var, 0)
+ && host_integerp (compare_base, 0))
+ {
+ int probability;
+ HOST_WIDE_INT compare_count;
+ HOST_WIDE_INT loop_bound = tree_low_cst (loop_bound_var, 0);
+ HOST_WIDE_INT compare_bound = tree_low_cst (compare_var, 0);
+ HOST_WIDE_INT base = tree_low_cst (compare_base, 0);
+ HOST_WIDE_INT loop_count = (loop_bound - base) / compare_step;
+
+ if ((compare_step > 0)
+ ^ (compare_code == LT_EXPR || compare_code == LE_EXPR))
+ compare_count = (loop_bound - compare_bound) / compare_step;
+ else
+ compare_count = (compare_bound - base) / compare_step;
+
+ if (compare_code == LE_EXPR || compare_code == GE_EXPR)
+ compare_count ++;
+ if (loop_bound_code == LE_EXPR || loop_bound_code == GE_EXPR)
+ loop_count ++;
+
+ if (loop_count == 0)
+ probability = 0;
+ else if (compare_count > loop_count)
+ probability = 1;
+ else
+ probability = REG_BR_PROB_BASE * compare_count / loop_count;
+ predict_edge (then_edge, PRED_LOOP_IV_COMPARE, probability);
+ return;
+ }
+
+ if ((loop_bound_code == LT_EXPR || loop_bound_code == LE_EXPR)
+ && (compare_code == LT_EXPR || compare_code == LE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else if ((loop_bound_code == GT_EXPR || loop_bound_code == GE_EXPR)
+ && (compare_code == GT_EXPR || compare_code == GE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else if (loop_bound_code == NE_EXPR)
+ {
+ /* If the loop backedge condition is "(i != bound)", we do
+ the comparison based on the step of IV:
+ * step < 0 : backedge condition is like (i > bound)
+ * step > 0 : backedge condition is like (i < bound) */
+ gcc_assert (loop_bound_step != 0);
+ if (loop_bound_step > 0
+ && (compare_code == LT_EXPR
+ || compare_code == LE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else if (loop_bound_step < 0
+ && (compare_code == GT_EXPR
+ || compare_code == GE_EXPR))
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, TAKEN);
+ else
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
+ }
+ else
+ /* The branch is predicted not-taken if loop_bound_code is
+ opposite with compare_code. */
+ predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE, NOT_TAKEN);
+}
+
/* Predict edge probabilities by exploiting loop structure. */
static void
@@ -963,6 +1289,12 @@
VEC (edge, heap) *exits;
struct tree_niter_desc niter_desc;
edge ex;
+ struct nb_iter_bound *nb_iter;
+ enum tree_code loop_bound_code = ERROR_MARK;
+ int loop_bound_step = 0;
+ tree loop_bound_var = NULL;
+ tree loop_iv_base = NULL;
+ gimple stmt = NULL;
exits = get_loop_exit_edges (loop);
n_exits = VEC_length (edge, exits);
@@ -1010,6 +1342,25 @@
}
VEC_free (edge, heap, exits);
+ /* Find information about loop bound variables. */
+ for (nb_iter = loop->bounds; nb_iter;
+ nb_iter = nb_iter->next)
+ if (nb_iter->stmt
+ && gimple_code (nb_iter->stmt) == GIMPLE_COND)
+ {
+ stmt = nb_iter->stmt;
+ break;
+ }
+ if (!stmt && last_stmt (loop->header)
+ && gimple_code (last_stmt (loop->header)) == GIMPLE_COND)
+ stmt = last_stmt (loop->header);
+ if (stmt)
+ is_comparison_with_loop_invariant_p (stmt, loop,
+ &loop_bound_var,
+ &loop_bound_code,
+ &loop_bound_step,
+ &loop_iv_base);
+
bbs = get_loop_body (loop);
for (j = 0; j < loop->num_nodes; j++)
@@ -1071,6 +1422,10 @@
|| !flow_bb_inside_loop_p (loop, e->dest))
predict_edge (e, PRED_LOOP_EXIT, probability);
}
+ if (loop_bound_var)
+ predict_iv_comparison (loop, bb, loop_bound_var,
+ loop_bound_code,
+ loop_bound_step);
}
/* Free basic blocks from get_loop_body. */
===================================================================
@@ -116,3 +116,7 @@
/* Branches to a mudflap bounds check are extremely unlikely. */
DEF_PREDICTOR (PRED_MUDFLAP, "mudflap check", PROB_VERY_LIKELY, 0)
+
+/* Branches to compare induction variable to a loop bound is
+ extremely likely. */
+DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY, 0)