[llvm-commits] [llvm] r144527 - in /llvm/trunk: include/llvm/CodeGen/MachineBranchProbabilityInfo.h lib/CodeGen/MachineBranchProbabilityInfo.cpp

[Chandler Carruth]

Author: chandlerc
Date: Mon Nov 14 02:55:59 2011
New Revision: 144527

URL: http://llvm.org/viewvc/llvm-project?rev=144527&view=rev
Log:
Reuse the logic in getEdgeProbability within getHotSucc in order to
correctly handle blocks whose successor weights sum to more than
UINT32_MAX. This is slightly less efficient, but the entire thing is
already linear on the number of successors. Calling it within any hot
routine is a mistake, and indeed no one is calling it. It also
simplifies the code.

Modified:
    llvm/trunk/include/llvm/CodeGen/MachineBranchProbabilityInfo.h
    llvm/trunk/lib/CodeGen/MachineBranchProbabilityInfo.cpp

Modified: llvm/trunk/include/llvm/CodeGen/MachineBranchProbabilityInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineBranchProbabilityInfo.h?rev=144527&r1=144526&r2=144527&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineBranchProbabilityInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineBranchProbabilityInfo.h Mon Nov 14 02:55:59 2011
@@ -59,6 +59,7 @@
   bool isEdgeHot(MachineBasicBlock *Src, MachineBasicBlock *Dst) const;
 
   // Return a hot successor for the block BB or null if there isn't one.
+  // NB: This routine's complexity is linear on the number of successors.
   MachineBasicBlock *getHotSucc(MachineBasicBlock *MBB) const;
 
   // Return a probability as a fraction between 0 (0% probability) and

Modified: llvm/trunk/lib/CodeGen/MachineBranchProbabilityInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBranchProbabilityInfo.cpp?rev=144527&r1=144526&r2=144527&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBranchProbabilityInfo.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBranchProbabilityInfo.cpp Mon Nov 14 02:55:59 2011
@@ -76,26 +76,18 @@
 
 MachineBasicBlock *
 MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
-  uint32_t Sum = 0;
   uint32_t MaxWeight = 0;
   MachineBasicBlock *MaxSucc = 0;
-
   for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
        E = MBB->succ_end(); I != E; ++I) {
-    MachineBasicBlock *Succ = *I;
-    uint32_t Weight = getEdgeWeight(MBB, Succ);
-    uint32_t PrevSum = Sum;
-
-    Sum += Weight;
-    assert(Sum > PrevSum); (void) PrevSum;
-
+    uint32_t Weight = getEdgeWeight(MBB, *I);
     if (Weight > MaxWeight) {
       MaxWeight = Weight;
-      MaxSucc = Succ;
+      MaxSucc = *I;
     }
   }
 
-  if (BranchProbability(MaxWeight, Sum) >= BranchProbability(4, 5))
+  if (getEdgeProbability(MBB, MaxSucc) >= BranchProbability(4, 5))
     return MaxSucc;
 
   return 0;