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phiopt: Improve minmax optimization [PR95699]

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As discussed in the PR, the
x < 0x80000000U to (int) x >= 0
optimization stands in the way of minmax_replacement optimization,
so for comparisons with most of the constants it works well, but when the
above mentioned optimization triggers, it is unable to do it.
The match.pd (cond (cmp (convert? x) c1) (op x c2) c3) -> (op (minmax x c1) c2)
optimization is able to look through that and this patch
teaches minmax_replacement about it too.

2020-06-18  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/95699
	* tree-ssa-phiopt.c (minmax_replacement): Treat (signed int)x < 0
	as x > INT_MAX and (signed int)x >= 0 as x <= INT_MAX.  Move variable
	declarations to the statements that set them where possible.

	* gcc.dg/tree-ssa/pr95699.c: New test.
This commit is contained in:
Jakub Jelinek 2020-06-18 12:11:09 +02:00
parent 9a875db43c
commit 2e0f4a18bc
2 changed files with 92 additions and 10 deletions
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39
gcc/testsuite/gcc.dg/tree-ssa/pr95699.c Normal file
View file

@ -0,0 +1,39 @@
/* PR tree-optimization/95699 */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump "MAX_EXPR <\[^>\n\r]*9223372036854775807\[^>\n\r]*>" "optimized" } } */
/* { dg-final { scan-tree-dump "MAX_EXPR <\[^>\n\r]*9223372036854775808\[^>\n\r]*>" "optimized" } } */
/* { dg-final { scan-tree-dump "MIN_EXPR <\[^>\n\r]*9223372036854775807\[^>\n\r]*>" "optimized" } } */
/* { dg-final { scan-tree-dump "MIN_EXPR <\[^>\n\r]*9223372036854775808\[^>\n\r]*>" "optimized" } } */
unsigned long long
f1 (unsigned long long x)
{
if (x < 0x7fffffffffffffffULL)
x = 0x7fffffffffffffffULL;
return x;
}
unsigned long long
f2 (unsigned long long x)
{
if (x < 0x8000000000000000ULL)
x = 0x8000000000000000ULL;
return x;
}
unsigned long long
f3 (unsigned long long x)
{
if (x >= 0x7fffffffffffffffULL)
x = 0x7fffffffffffffffULL;
return x;
}
unsigned long long
f4 (unsigned long long x)
{
if (x >= 0x8000000000000000ULL)
x = 0x8000000000000000ULL;
return x;
}

63
gcc/tree-ssa-phiopt.c
View file

@ -1363,22 +1363,21 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
edge e0, edge e1, gimple *phi,
tree arg0, tree arg1)
{
tree result, type, rhs;
gcond *cond;
tree result;
edge true_edge, false_edge;
enum tree_code cmp, minmax, ass_code;
tree smaller, alt_smaller, larger, alt_larger, arg_true, arg_false;
enum tree_code minmax, ass_code;
tree smaller, larger, arg_true, arg_false;
gimple_stmt_iterator gsi, gsi_from;
type = TREE_TYPE (PHI_RESULT (phi));
tree type = TREE_TYPE (PHI_RESULT (phi));
/* The optimization may be unsafe due to NaNs. */
if (HONOR_NANS (type) || HONOR_SIGNED_ZEROS (type))
return false;
cond = as_a <gcond *> (last_stmt (cond_bb));
cmp = gimple_cond_code (cond);
rhs = gimple_cond_rhs (cond);
gcond *cond = as_a <gcond *> (last_stmt (cond_bb));
enum tree_code cmp = gimple_cond_code (cond);
tree rhs = gimple_cond_rhs (cond);
/* Turn EQ/NE of extreme values to order comparisons. */
if ((cmp == NE_EXPR || cmp == EQ_EXPR)
@ -1401,8 +1400,8 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
/* This transformation is only valid for order comparisons. Record which
operand is smaller/larger if the result of the comparison is true. */
alt_smaller = NULL_TREE;
alt_larger = NULL_TREE;
tree alt_smaller = NULL_TREE;
tree alt_larger = NULL_TREE;
if (cmp == LT_EXPR || cmp == LE_EXPR)
{
smaller = gimple_cond_lhs (cond);
@ -1463,6 +1462,50 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
else
return false;
/* Handle the special case of (signed_type)x < 0 being equivalent
to x > MAX_VAL(signed_type) and (signed_type)x >= 0 equivalent
to x <= MAX_VAL(signed_type). */
if ((cmp == GE_EXPR || cmp == LT_EXPR)
&& INTEGRAL_TYPE_P (type)
&& TYPE_UNSIGNED (type)
&& integer_zerop (rhs))
{
tree op = gimple_cond_lhs (cond);
if (TREE_CODE (op) == SSA_NAME
&& INTEGRAL_TYPE_P (TREE_TYPE (op))
&& !TYPE_UNSIGNED (TREE_TYPE (op)))
{
gimple *def_stmt = SSA_NAME_DEF_STMT (op);
if (gimple_assign_cast_p (def_stmt))
{
tree op1 = gimple_assign_rhs1 (def_stmt);
if (INTEGRAL_TYPE_P (TREE_TYPE (op1))
&& TYPE_UNSIGNED (TREE_TYPE (op1))
&& (TYPE_PRECISION (TREE_TYPE (op))
== TYPE_PRECISION (TREE_TYPE (op1)))
&& useless_type_conversion_p (type, TREE_TYPE (op1)))
{
wide_int w1 = wi::max_value (TREE_TYPE (op));
wide_int w2 = wi::add (w1, 1);
if (cmp == LT_EXPR)
{
larger = op1;
smaller = wide_int_to_tree (TREE_TYPE (op1), w1);
alt_smaller = wide_int_to_tree (TREE_TYPE (op1), w2);
alt_larger = NULL_TREE;
}
else
{
smaller = op1;
larger = wide_int_to_tree (TREE_TYPE (op1), w1);
alt_larger = wide_int_to_tree (TREE_TYPE (op1), w2);
alt_smaller = NULL_TREE;
}
}
}
}
}
/* We need to know which is the true edge and which is the false
edge so that we know if have abs or negative abs. */
extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);