[Bug 101442] Piglit shaders@ssa@fs-if-def-else-break fails with sb but passes with R600_DEBUG=nosb - bugzilla-daemon

From: bugzilla-daemon@freedesktop.org
To: dri-devel@lists.freedesktop.org
Subject: [Bug 101442] Piglit shaders@ssa@fs-if-def-else-break fails with sb but passes with R600_DEBUG=nosb
Date: Sat, 27 Jan 2018 21:00:57 +0000	[thread overview]
Message-ID: <bug-101442-502-PW0BDRM9K9@http.bugs.freedesktop.org/> (raw)
In-Reply-To: <bug-101442-502@http.bugs.freedesktop.org/>

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https://bugs.freedesktop.org/show_bug.cgi?id=101442

--- Comment #5 from Gert Wollny <gw.fossdev@gmail.com> ---
With a bit more digging I found out that the sb optimizer simply drops the ELSE
if no ALU instructions are found in the else branch, i.e. 

   while(cond1)
      if (cond2) {
          a = b + c; 
      } else {
          break; 
      }
   }

becomes 

   while(cond1)
      if (cond2) {
         a = b + c; 
         break; 
   }
}

after the first sb/dce_cleanup pass, and this is obviously wrong. With the
break in the if path this is not a problem. I'll attach two piglits that
illustrate the behaviour.

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