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

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);