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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72426 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index aae76873d0..26c036269d 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/include/llvm/CodeGen/LiveVariables.h
@@ -33,6 +33,7 @@
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SparseBitVector.h"
 
 namespace llvm {
 
@@ -75,7 +76,7 @@ public:
     /// through.  This is a bit set which uses the basic block number as an
     /// index.
     ///
-    BitVector AliveBlocks;
+    SparseBitVector<> AliveBlocks;
 
     /// NumUses - Number of uses of this register across the entire function.
     ///