LiveVariables::VarInfo contains an AliveBlocks BitVector, which has as many

entries as there are basic blocks in the function.  LiveVariables::getVarInfo
creates a VarInfo struct for every register in the function, leading to
quadratic space use.  This patch changes the BitVector to a SparseBitVector,
which doesn't help the worst-case memory use but does reduce the actual use in
very long functions with short-lived variables.

llvm-svn: 72426

1 files changed, 2 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index 2eacb086d8b..c5c76fc7946 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -334,8 +334,7 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
 
       // Is it alive in this successor?
       unsigned SuccIdx = SuccMBB->getNumber();
-      if (SuccIdx < InRegVI.AliveBlocks.size() &&
-          InRegVI.AliveBlocks[SuccIdx]) {
+      if (InRegVI.AliveBlocks.test(SuccIdx)) {
         ValueIsLive = true;
         break;
       }
@@ -407,8 +406,7 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
 
       // This vreg no longer lives all of the way through opBlock.
       unsigned opBlockNum = opBlock.getNumber();
-      if (opBlockNum < InRegVI.AliveBlocks.size())
-        InRegVI.AliveBlocks[opBlockNum] = false;
+      InRegVI.AliveBlocks.reset(opBlockNum);
     }
   }