[llvm-commits] [llvm] r103933 - /llvm/trunk/lib/CodeGen/RegAllocFast.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Sun May 16 22:26:06 2010
New Revision: 103933

URL: http://llvm.org/viewvc/llvm-project?rev=103933&view=rev
Log:
Execute virtreg kills immediately instead of after processing all uses.

This is safe to do because the physreg has been marked UsedInInstr and the kill flag will be set on the last operand using the virtreg if there are more then one.

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

Modified: llvm/trunk/lib/CodeGen/RegAllocFast.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegAllocFast.cpp?rev=103933&r1=103932&r2=103933&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegAllocFast.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegAllocFast.cpp Sun May 16 22:26:06 2010
@@ -563,6 +563,7 @@
   bool New;
   tie(LRI, New) = LiveVirtRegs.insert(std::make_pair(VirtReg, LiveReg()));
   LiveReg &LR = LRI->second;
+  MachineOperand &MO = MI->getOperand(OpNum);
   if (New) {
     allocVirtReg(MI, *LRI, Hint);
     const TargetRegisterClass *RC = MRI->getRegClass(VirtReg);
@@ -572,7 +573,6 @@
     TII->loadRegFromStackSlot(*MBB, MI, LR.PhysReg, FrameIndex, RC, TRI);
     ++NumLoads;
   } else if (LR.Dirty) {
-    MachineOperand &MO = MI->getOperand(OpNum);
     if (isLastUseOfLocalReg(MO)) {
       DEBUG(dbgs() << "Killing last use: " << MO << "\n");
       MO.setIsKill();
@@ -580,6 +580,13 @@
       DEBUG(dbgs() << "Clearing dubious kill: " << MO << "\n");
       MO.setIsKill(false);
     }
+  } else if (MO.isKill()) {
+    // We must remove kill flags from uses of reloaded registers because the
+    // register would be killed immediately, and there might be a second use:
+    //   %foo = OR %x<kill>, %x
+    // This would cause a second reload of %x into a different register.
+    DEBUG(dbgs() << "Clearing clean kill: " << MO << "\n");
+    MO.setIsKill(false);
   }
   assert(LR.PhysReg && "Register not assigned");
   LR.LastUse = MI;
@@ -630,7 +637,7 @@
          E = MBB->livein_end(); I != E; ++I)
     definePhysReg(MII, *I, regReserved);
 
-  SmallVector<unsigned, 8> VirtKills, PhysDefs;
+  SmallVector<unsigned, 8> PhysECs;
   SmallVector<MachineInstr*, 32> Coalesced;
 
   // Otherwise, sequentially allocate each instruction in the MBB.
@@ -694,7 +701,7 @@
 
     // Track registers used by instruction.
     UsedInInstr.reset();
-    PhysDefs.clear();
+    PhysECs.clear();
 
     // First scan.
     // Mark physreg uses and early clobbers as used.
@@ -714,7 +721,7 @@
         usePhysReg(MO);
       } else if (MO.isEarlyClobber()) {
         definePhysReg(MI, Reg, MO.isDead() ? regFree : regReserved);
-        PhysDefs.push_back(Reg);
+        PhysECs.push_back(Reg);
       }
     }
 
@@ -730,25 +737,20 @@
         unsigned PhysReg = reloadVirtReg(MI, i, Reg, CopyDst);
         CopySrc = (CopySrc == Reg || CopySrc == PhysReg) ? PhysReg : 0;
         if (setPhysReg(MO, PhysReg))
-          VirtKills.push_back(Reg);
+          killVirtReg(Reg);
       } else if (MO.isEarlyClobber()) {
         unsigned PhysReg = defineVirtReg(MI, i, Reg, 0);
         setPhysReg(MO, PhysReg);
-        PhysDefs.push_back(PhysReg);
+        PhysECs.push_back(PhysReg);
       }
     }
 
-    // Process virtreg kills
-    for (unsigned i = 0, e = VirtKills.size(); i != e; ++i)
-      killVirtReg(VirtKills[i]);
-    VirtKills.clear();
-
     MRI->addPhysRegsUsed(UsedInInstr);
 
     // Track registers defined by instruction - early clobbers at this point.
     UsedInInstr.reset();
-    for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i) {
-      unsigned PhysReg = PhysDefs[i];
+    for (unsigned i = 0, e = PhysECs.size(); i != e; ++i) {
+      unsigned PhysReg = PhysECs[i];
       UsedInInstr.set(PhysReg);
       for (const unsigned *AS = TRI->getAliasSet(PhysReg);
             unsigned Alias = *AS; ++AS)
@@ -781,17 +783,12 @@
       }
       unsigned PhysReg = defineVirtReg(MI, i, Reg, CopySrc);
       if (setPhysReg(MO, PhysReg)) {
-        VirtKills.push_back(Reg);
+        killVirtReg(Reg);
         CopyDst = 0; // cancel coalescing;
       } else
         CopyDst = (CopyDst == Reg || CopyDst == PhysReg) ? PhysReg : 0;
     }
 
-    // Process virtreg deads.
-    for (unsigned i = 0, e = VirtKills.size(); i != e; ++i)
-      killVirtReg(VirtKills[i]);
-    VirtKills.clear();
-
     MRI->addPhysRegsUsed(UsedInInstr);
 
     if (CopyDst && CopyDst == CopySrc && CopyDstSub == CopySrcSub) {