[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

diff --git a/llvm/include/llvm/CodeGen/LiveVariables.h b/llvm/include/llvm/CodeGen/LiveVariables.h
index efb0fa8..815f779 100644 (file)
--- a/llvm/include/llvm/CodeGen/LiveVariables.h
+++ b/llvm/include/llvm/CodeGen/LiveVariables.h
@@ -274,9 +274,10 @@ public:
 
   void MarkVirtRegAliveInBlock(VarInfo& VRInfo, MachineBasicBlock* DefBlock,
                                MachineBasicBlock *BB);
-  void MarkVirtRegAliveInBlock(VarInfo& VRInfo, MachineBasicBlock* DefBlock,
+  void MarkVirtRegAliveInBlock(VarInfo &VRInfo, MachineBasicBlock *DefBlock,
                                MachineBasicBlock *BB,
-                               std::vector<MachineBasicBlock*> &WorkList);
+                               SmallVectorImpl<MachineBasicBlock *> &WorkList);
+
   void HandleVirtRegDef(unsigned reg, MachineInstr &MI);
   void HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB, MachineInstr &MI);
 

diff --git a/llvm/lib/CodeGen/LiveVariables.cpp b/llvm/lib/CodeGen/LiveVariables.cpp
index 6610491..4fba8f3 100644 (file)
--- 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()) {