CodeGen: Tune the SmallVector size in LiveRange

The vast majority of LiveRanges (ie, 4/5) have exactly 1 segment and 1
value number, and a good chunk of the rest have 2 of each, so
allocating space for 4 is wasteful. This is especially noticeable when
dealing with a very large number of vregs, and I have an internal case
where dropping this to 2 shaves over 5% off of peak memory when
compiling a particularly large function.

llvm-svn: 262681

diff --git a/llvm/include/llvm/CodeGen/LiveInterval.h b/llvm/include/llvm/CodeGen/LiveInterval.h
index 27c5355..1772809 100644 (file)
--- a/llvm/include/llvm/CodeGen/LiveInterval.h
+++ b/llvm/include/llvm/CodeGen/LiveInterval.h
@@ -190,8 +190,8 @@ namespace llvm {
       void dump() const;
     };
 
-    typedef SmallVector<Segment,4> Segments;
-    typedef SmallVector<VNInfo*,4> VNInfoList;
+    typedef SmallVector<Segment, 2> Segments;
+    typedef SmallVector<VNInfo *, 2> VNInfoList;
 
     Segments segments;   // the liveness segments
     VNInfoList valnos;   // value#'s