From: Richard Biener <rguenther@suse.de>
Date: Tue, 2 Sep 2025 08:16:28 +0000 (+0200)
Subject: tree-optimization/121753 - ICE with pattern breaking reduction constraints
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=edeb5b8258382a58e1ce8e1e79e61386250d42b2;p=thirdparty%2Fgcc.git

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 64a49cccc24..d0bf2f9e799 100644
--- 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;
 	  }