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re PR middle-end/62263 (Good codegen for bitwise rotate requires code that is technically undefined behavior)

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PR middle-end/62263
	PR middle-end/82498
	* tree-ssa-phiopt.c (value_replacement): Comment fix.  Handle
	up to 2 preparation statements for ASSIGN in MIDDLE_BB.

	* c-c++-common/rotate-8.c: Expect no PHIs in optimized dump.

From-SVN: r253761
This commit is contained in:
Jakub Jelinek 2017-10-14 20:48:38 +02:00 committed by Jakub Jelinek
parent cc453086d2
commit 14745bcac0
4 changed files with 118 additions and 7 deletions
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5
gcc/ChangeLog
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@ -1,5 +1,10 @@
2017-10-14 Jakub Jelinek <jakub@redhat.com>
PR middle-end/62263
PR middle-end/82498
* tree-ssa-phiopt.c (value_replacement): Comment fix. Handle
up to 2 preparation statements for ASSIGN in MIDDLE_BB.
PR middle-end/62263
PR middle-end/82498
* tree-ssa-forwprop.c (simplify_rotate): Allow def_arg1[N]

4
gcc/testsuite/ChangeLog
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@ -1,5 +1,9 @@
2017-10-14 Jakub Jelinek <jakub@redhat.com>
PR middle-end/62263
PR middle-end/82498
* c-c++-common/rotate-8.c: Expect no PHIs in optimized dump.
PR middle-end/62263
PR middle-end/82498
* c-c++-common/rotate-5.c (f2): New function. Move old

1
gcc/testsuite/c-c++-common/rotate-8.c
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@ -3,6 +3,7 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fno-ipa-icf -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump-times "r\[<>]\[<>]" 23 "optimized" } } */
/* { dg-final { scan-tree-dump-not "PHI <" "optimized" } } */
unsigned int
f1 (unsigned int x, unsigned char y)

115
gcc/tree-ssa-phiopt.c
View File

@ -995,11 +995,13 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
}
/* Now optimize (x != 0) ? x + y : y to just y.
The following condition is too restrictive, there can easily be another
stmt in middle_bb, for instance a CONVERT_EXPR for the second argument. */
gimple *assign = last_and_only_stmt (middle_bb);
if (!assign || gimple_code (assign) != GIMPLE_ASSIGN
/* Now optimize (x != 0) ? x + y : y to just x + y. */
gsi = gsi_last_nondebug_bb (middle_bb);
if (gsi_end_p (gsi))
return 0;
gimple *assign = gsi_stmt (gsi);
if (!is_gimple_assign (assign)
|| gimple_assign_rhs_class (assign) != GIMPLE_BINARY_RHS
|| (!INTEGRAL_TYPE_P (TREE_TYPE (arg0))
&& !POINTER_TYPE_P (TREE_TYPE (arg0))))
@ -1009,6 +1011,71 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
if (!gimple_seq_empty_p (phi_nodes (middle_bb)))
return 0;
/* Allow up to 2 cheap preparation statements that prepare argument
for assign, e.g.:
if (y_4 != 0)
goto <bb 3>;
else
goto <bb 4>;
<bb 3>:
_1 = (int) y_4;
iftmp.0_6 = x_5(D) r<< _1;
<bb 4>:
# iftmp.0_2 = PHI <iftmp.0_6(3), x_5(D)(2)>
or:
if (y_3(D) == 0)
goto <bb 4>;
else
goto <bb 3>;
<bb 3>:
y_4 = y_3(D) & 31;
_1 = (int) y_4;
_6 = x_5(D) r<< _1;
<bb 4>:
# _2 = PHI <x_5(D)(2), _6(3)> */
gimple *prep_stmt[2] = { NULL, NULL };
int prep_cnt;
for (prep_cnt = 0; ; prep_cnt++)
{
gsi_prev_nondebug (&gsi);
if (gsi_end_p (gsi))
break;
gimple *g = gsi_stmt (gsi);
if (gimple_code (g) == GIMPLE_LABEL)
break;
if (prep_cnt == 2 || !is_gimple_assign (g))
return 0;
tree lhs = gimple_assign_lhs (g);
tree rhs1 = gimple_assign_rhs1 (g);
use_operand_p use_p;
gimple *use_stmt;
if (TREE_CODE (lhs) != SSA_NAME
|| TREE_CODE (rhs1) != SSA_NAME
|| !INTEGRAL_TYPE_P (TREE_TYPE (lhs))
|| !INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
|| !single_imm_use (lhs, &use_p, &use_stmt)
|| use_stmt != (prep_cnt ? prep_stmt[prep_cnt - 1] : assign))
return 0;
switch (gimple_assign_rhs_code (g))
{
CASE_CONVERT:
break;
case PLUS_EXPR:
case BIT_AND_EXPR:
case BIT_IOR_EXPR:
case BIT_XOR_EXPR:
if (TREE_CODE (gimple_assign_rhs2 (g)) != INTEGER_CST)
return 0;
break;
default:
return 0;
}
prep_stmt[prep_cnt] = g;
}
/* Only transform if it removes the condition. */
if (!single_non_singleton_phi_for_edges (phi_nodes (gimple_bb (phi)), e0, e1))
return 0;
@ -1019,7 +1086,7 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
&& profile_status_for_fn (cfun) != PROFILE_ABSENT
&& EDGE_PRED (middle_bb, 0)->probability < profile_probability::even ()
/* If assign is cheap, there is no point avoiding it. */
&& estimate_num_insns (assign, &eni_time_weights)
&& estimate_num_insns (bb_seq (middle_bb), &eni_time_weights)
>= 3 * estimate_num_insns (cond, &eni_time_weights))
return 0;
@ -1030,6 +1097,32 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
tree cond_lhs = gimple_cond_lhs (cond);
tree cond_rhs = gimple_cond_rhs (cond);
/* Propagate the cond_rhs constant through preparation stmts,
make sure UB isn't invoked while doing that. */
for (int i = prep_cnt - 1; i >= 0; --i)
{
gimple *g = prep_stmt[i];
tree grhs1 = gimple_assign_rhs1 (g);
if (!operand_equal_for_phi_arg_p (cond_lhs, grhs1))
return 0;
cond_lhs = gimple_assign_lhs (g);
cond_rhs = fold_convert (TREE_TYPE (grhs1), cond_rhs);
if (TREE_CODE (cond_rhs) != INTEGER_CST
|| TREE_OVERFLOW (cond_rhs))
return 0;
if (gimple_assign_rhs_class (g) == GIMPLE_BINARY_RHS)
{
cond_rhs = int_const_binop (gimple_assign_rhs_code (g), cond_rhs,
gimple_assign_rhs2 (g));
if (TREE_OVERFLOW (cond_rhs))
return 0;
}
cond_rhs = fold_convert (TREE_TYPE (cond_lhs), cond_rhs);
if (TREE_CODE (cond_rhs) != INTEGER_CST
|| TREE_OVERFLOW (cond_rhs))
return 0;
}
if (((code == NE_EXPR && e1 == false_edge)
|| (code == EQ_EXPR && e1 == true_edge))
&& arg0 == lhs
@ -1071,7 +1164,15 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
duplicate_ssa_name_range_info (lhs, SSA_NAME_RANGE_TYPE (phires),
phires_range_info);
}
gimple_stmt_iterator gsi_from = gsi_for_stmt (assign);
gimple_stmt_iterator gsi_from;
for (int i = prep_cnt - 1; i >= 0; --i)
{
tree plhs = gimple_assign_lhs (prep_stmt[i]);
SSA_NAME_RANGE_INFO (plhs) = NULL;
gsi_from = gsi_for_stmt (prep_stmt[i]);
gsi_move_before (&gsi_from, &gsi);
}
gsi_from = gsi_for_stmt (assign);
gsi_move_before (&gsi_from, &gsi);
replace_phi_edge_with_variable (cond_bb, e1, phi, lhs);
return 2;