https://bugs.gentoo.org/750905
https://gcc.gnu.org/PR94163

From db3584552871c8caccdc22e97ea1573da9458253 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Fri, 13 Mar 2020 13:56:26 +0100
Subject: [PATCH] tree-optimization/94163 constrain alignment set by PRE

This avoids HWI -> unsigned truncation to end up with zero alignment
which set_ptr_info_alignment ICEs on.

2020-03-13  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/94163
	* tree-ssa-pre.c (create_expression_by_pieces): Check
	whether alignment would be zero.
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -2810,7 +2810,8 @@ create_expression_by_pieces (basic_block block, pre_expr expr,
 	      unsigned HOST_WIDE_INT hmisalign
 		= args.length () == 3 ? tree_to_uhwi (args[2]) : 0;
 	      if ((halign & (halign - 1)) == 0
-		  && (hmisalign & ~(halign - 1)) == 0)
+		  && (hmisalign & ~(halign - 1)) == 0
+		  && (unsigned int)halign != 0)
 		set_ptr_info_alignment (get_ptr_info (forcedname),
 					halign, hmisalign);
 	    }
-- 
2.29.2