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predict.c (find_qualified_ssa_name): New

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2012-05-08  Dehao Chen  <dehao@google.com>
gcc/
	* predict.c (find_qualified_ssa_name): New
	(find_ssa_name_in_expr): New
	(find_ssa_name_in_assign_stmt): New
	(is_comparison_with_loop_invariant_p): New
	(is_bound_expr_similar): New
	(predict_iv_comparison): New
	(predict_loops): Add heuristic for loop-nested branches that compare an
	induction variable to a loop bound variable.
	* predict.def (PRED_LOOP_IV_COMPARE): New macro
testsuite/
	* gcc.dg/predict-1.c: Check if LOOP_IV_COMPARE static predict
	heuristic is working properly.
	* gcc.dg/predict-2.c: Likewise.
	* gcc/dg/predict-3.c: Likewise.
	* gcc/dg/predict-4.c: Likewise.
	* gcc/dg/predict-5.c: Likewise.
	* gcc/dg/predict-6.c: Likewise.

From-SVN: r187277
This commit is contained in:
Dehao Chen 2012-05-08 10:01:44 +00:00 committed by Dehao Chen
parent 536b0cb7af
commit 9c04723a04
10 changed files with 706 additions and 0 deletions
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12
gcc/ChangeLog
View File

@ -1,3 +1,15 @@
2012-05-08 Dehao Chen <dehao@google.com>
* predict.c (find_qualified_ssa_name): New
(find_ssa_name_in_expr): New
(find_ssa_name_in_assign_stmt): New
(is_comparison_with_loop_invariant_p): New
(is_bound_expr_similar): New
(predict_iv_comparison): New
(predict_loops): Add heuristic for loop-nested branches that compare an
induction variable to a loop bound variable.
* predict.def (PRED_LOOP_IV_COMPARE): New macro
2012-05-08 Uros Bizjak <ubizjak@gmail.com>
* config/i386/i386.c (has_dispatch): Use TARGET_BDVER1 and

378
gcc/predict.c
View File

@ -946,6 +946,355 @@ combine_predictions_for_bb (basic_block bb)
}
}
/* 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
strips_small_constant (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 (host_integerp (t1, 0))
value = tree_low_cst (t1, 0);
else
return NULL;
if (!t2)
return ret;
else if (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 SSA_NAME cannot be found. */
static tree
get_base_value (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 strips_small_constant (TREE_OPERAND (t, 0), NULL);
case 2:
return strips_small_constant (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 = get_base_value (bound);
if (!bound)
return false;
if (TREE_CODE (base) != INTEGER_CST)
base = get_base_value (base);
if (!base)
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 are value coherent. */
static bool
expr_coherent_p (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 with LOOP_IV_BASE_VAR 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,
tree loop_iv_base_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_GUESS, TAKEN);
return;
}
else if (compare_code == EQ_EXPR)
{
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, NOT_TAKEN);
return;
}
if (!expr_coherent_p (loop_iv_base_var, compare_base))
return;
/* If loop bound, base and compare bound are all constants, we can
calculate the probability directly. */
if (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 (compare_count < 0)
compare_count = 0;
if (loop_count < 0)
loop_count = 0;
if (loop_count == 0)
probability = 0;
else if (compare_count > loop_count)
probability = REG_BR_PROB_BASE;
else
probability = (double) REG_BR_PROB_BASE * compare_count / loop_count;
predict_edge (then_edge, PRED_LOOP_IV_COMPARE, probability);
return;
}
if (expr_coherent_p (loop_bound_var, compare_var))
{
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_GUESS, 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_GUESS, 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_GUESS, TAKEN);
else if (loop_bound_step < 0
&& (compare_code == GT_EXPR
|| compare_code == GE_EXPR))
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN);
else
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, 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_GUESS, NOT_TAKEN);
}
else if (expr_coherent_p (loop_iv_base_var, compare_var))
{
/* For cases like:
for (i = s; i < h; i++)
if (i > s + 2) ....
The branch should be predicted taken. */
if (loop_bound_step > 0
&& (compare_code == GT_EXPR || compare_code == GE_EXPR))
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN);
else if (loop_bound_step < 0
&& (compare_code == LT_EXPR || compare_code == LE_EXPR))
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN);
else
predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, NOT_TAKEN);
}
}
/* Predict edge probabilities by exploiting loop structure. */
static void
@ -963,6 +1312,12 @@ predict_loops (void)
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 +1365,25 @@ predict_loops (void)
}
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 +1445,10 @@ predict_loops (void)
|| !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_iv_base,
loop_bound_code,
loop_bound_step);
}
/* Free basic blocks from get_loop_body. */

10
gcc/predict.def
View File

@ -116,3 +116,13 @@ DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (90), 0)
/* 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_GUESS, "guess loop iv compare",
PROB_VERY_LIKELY, 0)
/* Use number of loop iterations determined by # of iterations analysis
to set probability of branches that compares IV to loop bound variable. */
DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY,
PRED_FLAG_FIRST_MATCH)

10
gcc/testsuite/ChangeLog
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@ -1,3 +1,13 @@
2012-05-08 Dehao Chen <dehao@google.com>
* gcc.dg/predict-1.c: Check if LOOP_IV_COMPARE static predict
heuristic is working properly.
* gcc.dg/predict-2.c: Likewise.
* gcc/dg/predict-3.c: Likewise.
* gcc/dg/predict-4.c: Likewise.
* gcc/dg/predict-5.c: Likewise.
* gcc/dg/predict-6.c: Likewise.
2012-05-07 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/53239

54
gcc/testsuite/gcc.dg/predict-1.c Normal file
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@ -0,0 +1,54 @@
/* { 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);
if (i >= bound + 2)
global += bar (i);
if (i > bound - 2)
global += bar (i);
if (i + 2 > bound)
global += bar (i);
if (i == 10)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 0.0%" 5 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
/* { 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);
if (i >= bound + 2)
global += bar (i);
if (i > bound - 2)
global += bar (i);
if (i + 2 > bound)
global += bar (i);
if (i == 10)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 0.0%" 5 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */

54
gcc/testsuite/gcc.dg/predict-2.c Normal file
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@ -0,0 +1,54 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
extern int global;
int bar(int);
void foo (int base, int bound)
{
int i, ret = 0;
for (i = base; i < bound; i++)
{
if (i > bound * bound)
global += bar (i);
if (i > bound + 10)
global += bar (i);
if (i <= bound + 10)
global += bar (i);
if (i > base + 10)
global += bar (i);
if (i < base - 10)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-not "loop iv compare heuristics" "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
extern int global;
int bar(int);
void foo (int base, int bound)
{
int i, ret = 0;
for (i = base; i < bound; i++)
{
if (i > bound * bound)
global += bar (i);
if (i > bound + 10)
global += bar (i);
if (i <= bound + 10)
global += bar (i);
if (i > base + 10)
global += bar (i);
if (i < base - 10)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-not "loop iv compare heuristics" "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */

50
gcc/testsuite/gcc.dg/predict-3.c Normal file
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@ -0,0 +1,50 @@
/* { 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);
if (i <= bound)
global += bar (i);
if (i + 1 < bound)
global += bar (i);
if (i != bound)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 100.0%" 4 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
/* { 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);
if (i <= bound)
global += bar (i);
if (i + 1 < bound)
global += bar (i);
if (i != bound)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 100.0%" 4 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */

38
gcc/testsuite/gcc.dg/predict-4.c Normal file
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@ -0,0 +1,38 @@
/* { 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: 50.0%" "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
/* { 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: 50.0%" "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */

50
gcc/testsuite/gcc.dg/predict-5.c Normal file
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@ -0,0 +1,50 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
extern int global;
int bar (int);
void foo (int base, int bound)
{
int i, ret = 0;
for (i = base; i <= bound; i++)
{
if (i > base)
global += bar (i);
if (i > base + 1)
global += bar (i);
if (i >= base + 3)
global += bar (i);
if (i - 2 >= base)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 100.0%" 4 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
extern int global;
int bar (int);
void foo (int base, int bound)
{
int i, ret = 0;
for (i = base; i <= bound; i++)
{
if (i > base)
global += bar (i);
if (i > base + 1)
global += bar (i);
if (i >= base + 3)
global += bar (i);
if (i - 2 >= base)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 100.0%" 4 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */

50
gcc/testsuite/gcc.dg/predict-6.c Normal file
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@ -0,0 +1,50 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
extern int global;
int bar (int);
void foo (int base, int bound)
{
int i, ret = 0;
for (i = base; i <= bound; i++)
{
if (i < base)
global += bar (i);
if (i < base + 1)
global += bar (i);
if (i <= base + 3)
global += bar (i);
if (i - 1 < base)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 0.0%" 4 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
extern int global;
int bar (int);
void foo (int base, int bound)
{
int i, ret = 0;
for (i = base; i <= bound; i++)
{
if (i < base)
global += bar (i);
if (i < base + 1)
global += bar (i);
if (i <= base + 3)
global += bar (i);
if (i - 1 < base)
global += bar (i);
}
}
/* { dg-final { scan-tree-dump-times "loop iv compare heuristics: 0.0%" 4 "profile_estimate"} } */
/* { dg-final { cleanup-tree-dump "profile_estimate" } } */