[llvm-commits] [llvm] r114630 - /llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

[Evan Cheng]

Author: evancheng
Date: Thu Sep 23 01:51:55 2010
New Revision: 114630

URL: http://llvm.org/viewvc/llvm-project?rev=114630&view=rev
Log:
SDISel should not optimize a unconditional branch following a conditional branch
when the unconditional branch destination is the fallthrough block. The
canonicalization makes it easier to allow optimizations on DAGs to invert
conditional branches. The branch folding pass (and AnalyzeBranch) will clean up
the unnecessary unconditional branches later.

This is one of the patches leading up to disabling codegen prepare critical edge
splitting.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=114630&r1=114629&r2=114630&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Thu Sep 23 01:51:55 2010
@@ -1503,10 +1503,11 @@
                                MVT::Other, getControlRoot(), Cond,
                                DAG.getBasicBlock(CB.TrueBB));
 
-  // Insert the false branch.
-  if (CB.FalseBB != NextBlock)
-    BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, BrCond,
-                         DAG.getBasicBlock(CB.FalseBB));
+  // Insert the false branch. Do this even if it's a fall through branch,
+  // this makes it easier to do DAG optimizations which require inverting
+  // the branch condition.
+  BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, BrCond,
+                       DAG.getBasicBlock(CB.FalseBB));
 
   DAG.setRoot(BrCond);
 }