Do not count unused scalar use when marking STMT_VINFO_LIVE_P [PR113091]

When pattern recognition is involved, a statement whose definition is
consumed in some pattern, may not be included in the final replacement
pattern statements, and would be skipped when building SLP graph.

 * Original
  char a_c = *(char *) a;
  char b_c = *(char *) b;
  unsigned short a_s = (unsigned short) a_c;
  int a_i = (int) a_s;
  int b_i = (int) b_c;
  int r_i = a_i - b_i;

 * After pattern replacement
  a_s = (unsigned short) a_c;
  a_i = (int) a_s;

  patt_b_s = (unsigned short) b_c;    // b_i = (int) b_c
  patt_b_i = (int) patt_b_s;          // b_i = (int) b_c

  patt_r_s = widen_minus(a_c, b_c);   // r_i = a_i - b_i
  patt_r_i = (int) patt_r_s;          // r_i = a_i - b_i

The definitions of a_i(original statement) and b_i(pattern statement)
are related to, but actually not part of widen_minus pattern.
Vectorizing the pattern does not cause these definition statements to
be marked as PURE_SLP.  For this case, we need to recursively check
whether their uses are all absorbed into vectorized code.  But there
is an exception that some use may participate in an vectorized
operation via an external SLP node containing that use as an element.

gcc/ChangeLog:

	PR tree-optimization/113091
	* tree-vect-slp.cc (vect_slp_has_scalar_use): New function.
	(vect_bb_slp_mark_live_stmts): New parameter scalar_use_map, check
	scalar use with new function.
	(vect_bb_slp_mark_live_stmts): New function as entry to existing
	overriden functions with same name.
	(vect_slp_analyze_operations): Call new entry function to mark
	live statements.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/bb-slp-pr113091.c: New test.

0 files changed, 0 insertions, 0 deletions