https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114769
Bug ID: 114769
Summary: Suspicious code in vect_recog_sad_pattern()
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: fxue at os dot amperecomputing.com
Target Milestone: ---
This function may contain buggy code, which was introduced due to recent
support to the new ABD pattern. It calls "vect_recog_absolute_difference" to
check ABS/ABSU statement, if succeed, it expects that "vect_unpromoted_value
unprom[2]" is properly set for the two operands. Though, at the final code
snippet, this is missed, so "unprom" could have unwanted values.
/* Failed to find a widen operation so we check for a regular MINUS_EXPR. */
gassign *diff = dyn_cast <gassign *> (STMT_VINFO_STMT (diff_stmt_vinfo));
if (diff_stmt && diff
&& gimple_assign_rhs_code (diff) == MINUS_EXPR
&& TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (abs_oprnd)))
{
*diff_stmt = diff;
*half_type = NULL_TREE;
// unprom is not set accordingly
return true;
}
This execution path would be triggered for an architecture that merely support
dot-product instruction, but w/o "IFN_ABD" and "IFN_VEC_WIDEN_ABD"
instructions.
