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Remove inefficient branchless conditional negate optimization 

2015-03-06  Wilco Dijkstra  <wdijkstr@arm.com>

  gcc/
    * tree-ssa-phiopt.c (neg_replacement): Remove.
    (tree_ssa_phiopt_worker): Remove negate optimization.

  gcc/testsuite/
    * gcc.dg/tree-ssa/pr45685.c: Move to gcc.target/i386.
    * gcc.target/aarch64/csneg-1.c (test_csneg_cmp): New test.
    * gcc.target/i386/pr45685.c: Moved test, check for conditional move on x64.

From-SVN: r221246
This commit is contained in:
Wilco Dijkstra 2015-03-06 16:35:30 +00:00 committed by Jiong Wang
parent c271e224c2
commit 268cb4b373
5 changed files with 23 additions and 161 deletions
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5
gcc/ChangeLog
View File

@ -1,3 +1,8 @@
2015-03-06 Wilco Dijkstra <wilco.dijkstra@arm.com>
* tree-ssa-phiopt.c (neg_replacement): Remove.
(tree_ssa_phiopt_worker): Remove negate optimization.
2015-03-05 Jan Hubicka <hubicka@ucw.cz>
PR ipa/65302

7
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,10 @@
2015-03-06 Wilco Dijkstra <wilco.dijkstra@arm.com>
* gcc.dg/tree-ssa/pr45685.c: Move to gcc.target/i386.
* gcc.target/aarch64/csneg-1.c (test_csneg_cmp): New test.
* gcc.target/i386/pr45685.c: Moved test, check for conditional move on
x64.
2015-03-05 Jan Hubicka <hubicka@ucw.cz>
* g++.dg/lto/pr65302_1.C: New testcase.

8
gcc/testsuite/gcc.target/aarch64/csneg-1.c
View File

@ -48,3 +48,11 @@ test_csneg64_condasn2(long long x0,
x4 = (x0 == x1) ? x3 : -x2;
return x4;
}
int test_csneg_cmp(int x)
{
/* { dg-final { scan-assembler "csneg\tw\[0-9\]" } } */
if (x > 3)
x = -x;
return x;
}

8
gcc/testsuite/gcc.dg/tree-ssa/pr45685.c → gcc/testsuite/gcc.target/i386/pr45685.c
View File

@ -1,5 +1,5 @@
/* { dg-do compile } */
/* { dg-options "-O3 -fdump-tree-phiopt1-details" } */
/* { dg-do compile { target { ! { ia32 } } } } */
/* { dg-options "-O3" } */
typedef unsigned long int uint64_t;
typedef long int int64_t;
@ -36,6 +36,4 @@ int summation_helper_2(int64_t* products, uint64_t count)
return s;
}
/* { dg-final { scan-tree-dump-times "converted to straightline code" 2 "phiopt1" } } */
/* { dg-final { cleanup-tree-dump "phiopt1" } } */
/* { dg-final { scan-assembler-times "cmov" 4 } } */

156
gcc/tree-ssa-phiopt.c
View File

@ -96,8 +96,6 @@ static bool minmax_replacement (basic_block, basic_block,
edge, edge, gimple, tree, tree);
static bool abs_replacement (basic_block, basic_block,
edge, edge, gimple, tree, tree);
static bool neg_replacement (basic_block, basic_block,
edge, edge, gimple, tree, tree);
static bool cond_store_replacement (basic_block, basic_block, edge, edge,
hash_set<tree> *);
static bool cond_if_else_store_replacement (basic_block, basic_block, basic_block);
@ -209,23 +207,6 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads)
/* Calculate the set of non-trapping memory accesses. */
nontrap = get_non_trapping ();
/* The replacement of conditional negation with a non-branching
sequence is really only a win when optimizing for speed and we
can avoid transformations by gimple if-conversion that result
in poor RTL generation.
Ideally either gimple if-conversion or the RTL expanders will
be improved and the code to emit branchless conditional negation
can be removed. */
bool replace_conditional_negation = false;
if (!do_store_elim)
replace_conditional_negation
= ((!optimize_size && optimize >= 2)
|| (((flag_tree_loop_vectorize || cfun->has_force_vectorize_loops)
&& flag_tree_loop_if_convert != 0)
|| flag_tree_loop_if_convert == 1
|| flag_tree_loop_if_convert_stores == 1));
/* Search every basic block for COND_EXPR we may be able to optimize.
We walk the blocks in order that guarantees that a block with
@ -380,9 +361,6 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads)
cfgchanged = true;
else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
cfgchanged = true;
else if (replace_conditional_negation
&& neg_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
cfgchanged = true;
else if (minmax_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
cfgchanged = true;
}
@ -1319,140 +1297,6 @@ abs_replacement (basic_block cond_bb, basic_block middle_bb,
return true;
}
/* The function neg_replacement replaces conditional negation with
equivalent straight line code. Returns TRUE if replacement is done,
otherwise returns FALSE.
COND_BB branches around negation occuring in MIDDLE_BB.
E0 and E1 are edges out of COND_BB. E0 reaches MIDDLE_BB and
E1 reaches the other successor which should contain PHI with
arguments ARG0 and ARG1.
Assuming negation is to occur when the condition is true,
then the non-branching sequence is:
result = (rhs ^ -cond) + cond
Inverting the condition or its result gives us negation
when the original condition is false. */
static bool
neg_replacement (basic_block cond_bb, basic_block middle_bb,
edge e0 ATTRIBUTE_UNUSED, edge e1,
gimple phi, tree arg0, tree arg1)
{
gimple new_stmt, cond;
gimple_stmt_iterator gsi;
gimple assign;
edge true_edge, false_edge;
tree rhs, lhs;
enum tree_code cond_code;
bool invert = false;
/* This transformation performs logical operations on the
incoming arguments. So force them to be integral types. */
if (!INTEGRAL_TYPE_P (TREE_TYPE (arg0)))
return false;
/* OTHER_BLOCK must have only one executable statement which must have the
form arg0 = -arg1 or arg1 = -arg0. */
assign = last_and_only_stmt (middle_bb);
/* If we did not find the proper negation assignment, then we can not
optimize. */
if (assign == NULL)
return false;
/* If we got here, then we have found the only executable statement
in OTHER_BLOCK. If it is anything other than arg0 = -arg1 or
arg1 = -arg0, then we can not optimize. */
if (gimple_code (assign) != GIMPLE_ASSIGN)
return false;
lhs = gimple_assign_lhs (assign);
if (gimple_assign_rhs_code (assign) != NEGATE_EXPR)
return false;
rhs = gimple_assign_rhs1 (assign);
/* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
if (!(lhs == arg0 && rhs == arg1)
&& !(lhs == arg1 && rhs == arg0))
return false;
/* The basic sequence assumes we negate when the condition is true.
If we need the opposite, then we will either need to invert the
condition or its result. */
extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
invert = false_edge->dest == middle_bb;
/* Unlike abs_replacement, we can handle arbitrary conditionals here. */
cond = last_stmt (cond_bb);
cond_code = gimple_cond_code (cond);
/* If inversion is needed, first try to invert the test since
that's cheapest. */
if (invert)
{
bool honor_nans = HONOR_NANS (gimple_cond_lhs (cond));
enum tree_code new_code = invert_tree_comparison (cond_code, honor_nans);
/* If invert_tree_comparison was successful, then use its return
value as the new code and note that inversion is no longer
needed. */
if (new_code != ERROR_MARK)
{
cond_code = new_code;
invert = false;
}
}
tree cond_val = make_ssa_name (boolean_type_node);
new_stmt = gimple_build_assign (cond_val, cond_code,
gimple_cond_lhs (cond),
gimple_cond_rhs (cond));
gsi = gsi_last_bb (cond_bb);
gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
/* If we still need inversion, then invert the result of the
condition. */
if (invert)
{
tree tmp = make_ssa_name (boolean_type_node);
new_stmt = gimple_build_assign (tmp, BIT_XOR_EXPR, cond_val,
boolean_true_node);
gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
cond_val = tmp;
}
/* Get the condition in the right type so that we can perform
logical and arithmetic operations on it. */
tree cond_val_converted = make_ssa_name (TREE_TYPE (rhs));
new_stmt = gimple_build_assign (cond_val_converted, NOP_EXPR, cond_val);
gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
tree neg_cond_val_converted = make_ssa_name (TREE_TYPE (rhs));
new_stmt = gimple_build_assign (neg_cond_val_converted, NEGATE_EXPR,
cond_val_converted);
gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
tree tmp = make_ssa_name (TREE_TYPE (rhs));
new_stmt = gimple_build_assign (tmp, BIT_XOR_EXPR, rhs,
neg_cond_val_converted);
gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
tree new_lhs = make_ssa_name (TREE_TYPE (rhs));
new_stmt = gimple_build_assign (new_lhs, PLUS_EXPR, tmp, cond_val_converted);
gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
replace_phi_edge_with_variable (cond_bb, e1, phi, new_lhs);
/* Note that we optimized this PHI. */
return true;
}
/* Auxiliary functions to determine the set of memory accesses which
can't trap because they are preceded by accesses to the same memory
portion. We do that for MEM_REFs, so we only need to track