[llvm-commits] [llvm] r61027 - /llvm/trunk/lib/Transforms/Scalar/GVN.cpp

[Chris Lattner]

Author: lattner
Date: Sun Dec 14 23:28:29 2008
New Revision: 61027

URL: http://llvm.org/viewvc/llvm-project?rev=61027&view=rev
Log:
Enable Load PRE.  This teaches GVN to push partially redundant loads up the
CFG when there is exactly one predecessor where the load is not available.
This is designed to not increase code size but still eliminate partially
redundant loads.  This fires 1765 times on 403.gcc even though it doesn't
do critical edge splitting yet (the most common reason for it to fail).

Modified:
    llvm/trunk/lib/Transforms/Scalar/GVN.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=61027&r1=61026&r2=61027&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Sun Dec 14 23:28:29 2008
@@ -48,7 +48,7 @@
 
 static cl::opt<bool> EnablePRE("enable-pre",
                                cl::init(true), cl::Hidden);
-cl::opt<bool> EnableLoadPRE("enable-load-pre"/*, cl::init(true)*/);
+cl::opt<bool> EnableLoadPRE("enable-load-pre", cl::init(true));
 
 //===----------------------------------------------------------------------===//
 //                         ValueTable Class
@@ -957,6 +957,11 @@
   if (Deps.size() > 100)
     return false;
   
+  // If we had a phi translation failure, we'll have a single entry which is a
+  // clobber in the current block.  Reject this early.
+  if (Deps.size() == 1 && Deps[0].second.isClobber())
+    return false;
+  
   // Filter out useless results (non-locals, etc).  Keep track of the blocks
   // where we have a value available in repl, also keep track of whether we see
   // dependencies that produce an unknown value for the load (such as a call