[LiveVariables] Replace std::vector with SmallVector.

Replace std::vector with SmallVector to reduce the number of mallocs.
This method is frequently executed, and the number of elements in the
vector is typically small.

https://reviews.llvm.org/D83920

1 files changed, 4 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/LiveVariables.cpp b/llvm/lib/CodeGen/LiveVariables.cpp
index 6610491..4fba8f3 100644
--- a/llvm/lib/CodeGen/LiveVariables.cpp
+++ b/llvm/lib/CodeGen/LiveVariables.cpp
@@ -89,10 +89,9 @@ LiveVariables::VarInfo &LiveVariables::getVarInfo(unsigned RegIdx) {
   return VirtRegInfo[RegIdx];
 }
 
-void LiveVariables::MarkVirtRegAliveInBlock(VarInfo& VRInfo,
-                                            MachineBasicBlock *DefBlock,
-                                            MachineBasicBlock *MBB,
-                                    std::vector<MachineBasicBlock*> &WorkList) {
+void LiveVariables::MarkVirtRegAliveInBlock(
+    VarInfo &VRInfo, MachineBasicBlock *DefBlock, MachineBasicBlock *MBB,
+    SmallVectorImpl<MachineBasicBlock *> &WorkList) {
   unsigned BBNum = MBB->getNumber();
 
   // Check to see if this basic block is one of the killing blocks.  If so,
@@ -118,7 +117,7 @@ void LiveVariables::MarkVirtRegAliveInBlock(VarInfo& VRInfo,
 void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo,
                                             MachineBasicBlock *DefBlock,
                                             MachineBasicBlock *MBB) {
-  std::vector<MachineBasicBlock*> WorkList;
+  SmallVector<MachineBasicBlock *, 16> WorkList;
   MarkVirtRegAliveInBlock(VRInfo, DefBlock, MBB, WorkList);
 
   while (!WorkList.empty()) {