[llvm-commits] [llvm] r150288 - /llvm/trunk/lib/CodeGen/MachineLICM.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Fri Feb 10 18:44:19 2012
New Revision: 150288

URL: http://llvm.org/viewvc/llvm-project?rev=150288&view=rev
Log:
Allow Post-RA LICM to hoist reserved register reads.

When using register masks, registers like %rip are clobbered by the
register mask. LICM should still be able to hoist instructions reading
%rip from a loop containing calls.

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

Modified: llvm/trunk/lib/CodeGen/MachineLICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineLICM.cpp?rev=150288&r1=150287&r2=150288&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineLICM.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineLICM.cpp Fri Feb 10 18:44:19 2012
@@ -68,6 +68,7 @@
     MachineRegisterInfo *MRI;
     const InstrItineraryData *InstrItins;
     bool PreRegAlloc;
+    BitVector ReservedRegs;
 
     // Various analyses that we use...
     AliasAnalysis        *AA;      // Alias analysis info.
@@ -337,6 +338,8 @@
     for (TargetRegisterInfo::regclass_iterator I = TRI->regclass_begin(),
            E = TRI->regclass_end(); I != E; ++I)
       RegLimit[(*I)->getID()] = TRI->getRegPressureLimit(*I, MF);
+  } else {
+    ReservedRegs = TRI->getReservedRegs(MF);
   }
 
   // Get our Loop information...
@@ -426,6 +429,9 @@
            "Not expecting virtual register!");
 
     if (!MO.isDef()) {
+      // Allow reserved register reads to be hoisted.
+      if (ReservedRegs.test(Reg))
+        continue;
       if (Reg && (PhysRegDefs.test(Reg) || PhysRegClobbers.test(Reg)))
         // If it's using a non-loop-invariant register, then it's obviously not
         // safe to hoist.
@@ -531,6 +537,11 @@
         const MachineOperand &MO = MI->getOperand(j);
         if (!MO.isReg() || MO.isDef() || !MO.getReg())
           continue;
+        // Allow hoisting of reserved register reads that aren't call preserved.
+        // For example %rip.
+        // IsLoopInvariantInst() already checks MRI->isConstantPhysReg().
+        if (ReservedRegs.test(MO.getReg()))
+          continue;
         if (PhysRegDefs.test(MO.getReg()) ||
             PhysRegClobbers.test(MO.getReg())) {
           // If it's using a non-loop-invariant register, then it's obviously