[Bug tree-optimization/106293] [13 Regression] 456.hmmer at -Ofast -march=native regressed by 19% on zen2 and zen3 in July 2022

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106293

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot 
gnu.org

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Interesting.  It seems that early DSE is hindered by the extra PHI, possibly
not
reaching the CLOBBER.

@@ -24,6 +24,8 @@
     goto <bb 8>; [INV]

   <bb 3> :
+  # .MEM_10 = VDEF <.MEM_9>
+  g = &b;
   goto <bb 6>; [INV]

   <bb 4> :
@@ -39,7 +41,7 @@
     goto <bb 6>; [INV]

   <bb 6> :
-  # .MEM_5 = PHI <.MEM_9(3), .MEM_14(5)>
+  # .MEM_5 = PHI <.MEM_10(3), .MEM_14(5)>
   # VUSE <.MEM_5>
   d.3_4 = d;
   if (d.3_4 != 0)
@@ -48,7 +50,8 @@
     goto <bb 7>; [INV]

   <bb 7> :
-  # .MEM_12 = VDEF <.MEM_5>
+  # .MEM_17 = PHI <.MEM_5(6)>
+  # .MEM_12 = VDEF <.MEM_17>
   g ={v} {CLOBBER(eol)};