This small change reduces compile time for small programs on targets that have

large register files. The omission of Queries.clear() is perfectly safe because
LiveIntervalUnion::Query doesn't contain any data that needs freeing and
because LiveRegMatrix::runOnFunction happens to reset the OwningArrayPtr
holding Queries every time it is run, so there's no need to zero out the
queries either. Not having to do this for very large numbers of physregs
is a noticeable constant cost reduction in compilation of small programs.

llvm-svn: 200913

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LiveRegMatrix.cpp b/llvm/lib/CodeGen/LiveRegMatrix.cpp
index 1d801ac914a..7c943786635 100644
--- a/llvm/lib/CodeGen/LiveRegMatrix.cpp
+++ b/llvm/lib/CodeGen/LiveRegMatrix.cpp
@@ -65,7 +65,9 @@ bool LiveRegMatrix::runOnMachineFunction(MachineFunction &MF) {
 void LiveRegMatrix::releaseMemory() {
   for (unsigned i = 0, e = Matrix.size(); i != e; ++i) {
     Matrix[i].clear();
-    Queries[i].clear();
+    // No need to clear Queries here, since LiveIntervalUnion::Query doesn't
+    // have anything important to clear and LiveRegMatrix's runOnFunction()
+    // does a OwningPtr::reset anyways.
   }
 }