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tree-optimization/96370 - make reassoc expr rewrite more robust

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In the face of the more complex tricks in reassoc with respect
to negate processing it can happen that the expression rewrite
is fooled to recurse on a leaf and pick up a bogus expression
code.  The following patch makes the expression rewrite more
robust in providing the expression code to it directly since
it is the same for all operations in a chain.

2020-07-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/96370
	* tree-ssa-reassoc.c (rewrite_expr_tree): Add operation
	code parameter and use it instead of picking it up from
	the stmt that is being rewritten.
	(reassociate_bb): Pass down the operation code.

	* gcc.dg/pr96370.c: New testcase.
This commit is contained in:
Richard Biener 2020-07-30 10:24:42 +02:00
parent 8240f2f498
commit 2c558d2655
2 changed files with 13 additions and 5 deletions
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8
gcc/testsuite/gcc.dg/pr96370.c Normal file
View file

@ -0,0 +1,8 @@
/* { dg-do compile { target dfp } } */
/* { dg-options "-O2 -ffast-math" } */
void c(_Decimal128);
void a(_Decimal128 b)
{
c(-b * b);
}

10
gcc/tree-ssa-reassoc.c
View file

@ -4913,7 +4913,7 @@ insert_stmt_before_use (gimple *stmt, gimple *stmt_to_insert)
recursive invocations. */
static tree
rewrite_expr_tree (gimple *stmt, unsigned int opindex,
rewrite_expr_tree (gimple *stmt, enum tree_code rhs_code, unsigned int opindex,
vec<operand_entry *> ops, bool changed, bool next_changed)
{
tree rhs1 = gimple_assign_rhs1 (stmt);
@ -4960,7 +4960,7 @@ rewrite_expr_tree (gimple *stmt, unsigned int opindex,
= find_insert_point (stmt, oe1->op, oe2->op);
lhs = make_ssa_name (TREE_TYPE (lhs));
stmt
= gimple_build_assign (lhs, gimple_assign_rhs_code (stmt),
= gimple_build_assign (lhs, rhs_code,
oe1->op, oe2->op);
gimple_set_uid (stmt, uid);
gimple_set_visited (stmt, true);
@ -5004,7 +5004,7 @@ rewrite_expr_tree (gimple *stmt, unsigned int opindex,
/* Recurse on the LHS of the binary operator, which is guaranteed to
be the non-leaf side. */
tree new_rhs1
= rewrite_expr_tree (SSA_NAME_DEF_STMT (rhs1), opindex + 1, ops,
= rewrite_expr_tree (SSA_NAME_DEF_STMT (rhs1), rhs_code, opindex + 1, ops,
changed || oe->op != rhs2 || next_changed,
false);
@ -5030,7 +5030,7 @@ rewrite_expr_tree (gimple *stmt, unsigned int opindex,
gimple *insert_point = find_insert_point (stmt, new_rhs1, oe->op);
lhs = make_ssa_name (TREE_TYPE (lhs));
stmt = gimple_build_assign (lhs, gimple_assign_rhs_code (stmt),
stmt = gimple_build_assign (lhs, rhs_code,
new_rhs1, oe->op);
gimple_set_uid (stmt, uid);
gimple_set_visited (stmt, true);
@ -6477,7 +6477,7 @@ reassociate_bb (basic_block bb)
if (len >= 3)
swap_ops_for_binary_stmt (ops, len - 3, stmt);
new_lhs = rewrite_expr_tree (stmt, 0, ops,
new_lhs = rewrite_expr_tree (stmt, rhs_code, 0, ops,
powi_result != NULL
|| negate_result,
len != orig_len);