[llvm-commits] [llvm] r95832 - /llvm/trunk/lib/CodeGen/TailDuplication.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Wed Feb 10 18:34:33 2010
New Revision: 95832

URL: http://llvm.org/viewvc/llvm-project?rev=95832&view=rev
Log:
Reuse operand location when updating PHI instructions.

Calling RemoveOperand is very expensive on huge PHI instructions. This makes
early tail duplication run twice as fast on the Firefox JavaScript
interpreter.

Modified:
    llvm/trunk/lib/CodeGen/TailDuplication.cpp

Modified: llvm/trunk/lib/CodeGen/TailDuplication.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TailDuplication.cpp?rev=95832&r1=95831&r2=95832&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/TailDuplication.cpp (original)
+++ llvm/trunk/lib/CodeGen/TailDuplication.cpp Wed Feb 10 18:34:33 2010
@@ -403,26 +403,45 @@
             II->RemoveOperand(i);
           }
         }
-        II->RemoveOperand(Idx+1);
-        II->RemoveOperand(Idx);
-      }
+      } else
+        Idx = 0;
+
+      // If Idx is set, the operands at Idx and Idx+1 must be removed.
+      // We reuse the location to avoid expensive RemoveOperand calls.
+
       DenseMap<unsigned,AvailableValsTy>::iterator LI=SSAUpdateVals.find(Reg);
       if (LI != SSAUpdateVals.end()) {
         // This register is defined in the tail block.
         for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) {
           MachineBasicBlock *SrcBB = LI->second[j].first;
           unsigned SrcReg = LI->second[j].second;
-          II->addOperand(MachineOperand::CreateReg(SrcReg, false));
-          II->addOperand(MachineOperand::CreateMBB(SrcBB));
+          if (Idx != 0) {
+            II->getOperand(Idx).setReg(SrcReg);
+            II->getOperand(Idx+1).setMBB(SrcBB);
+            Idx = 0;
+          } else {
+            II->addOperand(MachineOperand::CreateReg(SrcReg, false));
+            II->addOperand(MachineOperand::CreateMBB(SrcBB));
+          }
         }
       } else {
         // Live in tail block, must also be live in predecessors.
         for (unsigned j = 0, ee = TDBBs.size(); j != ee; ++j) {
           MachineBasicBlock *SrcBB = TDBBs[j];
-          II->addOperand(MachineOperand::CreateReg(Reg, false));
-          II->addOperand(MachineOperand::CreateMBB(SrcBB));
+          if (Idx != 0) {
+            II->getOperand(Idx).setReg(Reg);
+            II->getOperand(Idx+1).setMBB(SrcBB);
+            Idx = 0;
+          } else {
+            II->addOperand(MachineOperand::CreateReg(Reg, false));
+            II->addOperand(MachineOperand::CreateMBB(SrcBB));
+          }
         }
       }
+      if (Idx != 0) {
+        II->RemoveOperand(Idx+1);
+        II->RemoveOperand(Idx);
+      }
     }
   }
 }