tree-optimization/121753 - ICE with pattern breaking reduction constraints

The recent change to vect_synth_mult_by_constant missed to handle
the synth_shift_p case for alg_shift, so we still changed c * 4
to c + c + c + c.  The following also amends alg_add_t2_m, alg_sub_t2_m,
alg_add_factor and alg_sub_factor appropriately.

	PR tree-optimization/121753
	* tree-vect-patterns.cc (vect_synth_mult_by_constant): Properly
	bail when synth_shift_p and an alg_shift use.  Handle other
	problematic cases.

diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index 64a49cccc2450ef061e2386cabfe1762c3c82a16..d0bf2f9e79906b52193d6d2228ea7a6c9bf386ec 100644 (file)
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -4329,7 +4329,14 @@ vect_synth_mult_by_constant (vec_info *vinfo, tree op, tree val,
          case alg_add_t2_m:
          case alg_sub_t2_m:
            op_uses++;
+           /* Fallthru.  */
+         case alg_shift:
+           if (synth_shift_p && alg.log[i])
+             return NULL;
            break;
+         case alg_add_factor:
+         case alg_sub_factor:
+           return NULL;
          default:
            break;
          }