[llvm-commits] [llvm] r60596 - in /llvm/trunk/lib: CodeGen/LiveIntervalAnalysis.cpp Target/X86/X86InstrInfo.cpp

[Evan Cheng]

Author: evancheng
Date: Fri Dec  5 11:41:31 2008
New Revision: 60596

URL: http://llvm.org/viewvc/llvm-project?rev=60596&view=rev
Log:
Reason #3 from 60595 doesn't hold true. If we can fold a PIC load from constpool into a use, the rewrite happens at time of spill (not in VirtRegMap). Later on, if the GlobalBaseReg is spilled, the spiller can see the use uses GlobalBaseReg and do the right thing.

Modified:
    llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp
    llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

Modified: llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp?rev=60596&r1=60595&r2=60596&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp Fri Dec  5 11:41:31 2008
@@ -2059,15 +2059,17 @@
           if (isLoadSS || ReMatDefMI->getDesc().canFoldAsLoad())
             Folded = tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index,
                                           Ops, isLoadSS, LdSlot, VReg);
-          unsigned ImpUse = getReMatImplicitUse(li, ReMatDefMI);
-          if (ImpUse) {
-            // Re-matting an instruction with virtual register use. Add the
-            // register as an implicit use on the use MI and update the register
-            // interval's spill weight to HUGE_VALF to prevent it from being
-            // spilled.
-            LiveInterval &ImpLi = getInterval(ImpUse);
-            ImpLi.weight = HUGE_VALF;
-            MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true));
+          if (!Folded) {
+            unsigned ImpUse = getReMatImplicitUse(li, ReMatDefMI);
+            if (ImpUse) {
+              // Re-matting an instruction with virtual register use. Add the
+              // register as an implicit use on the use MI and update the register
+              // interval's spill weight to HUGE_VALF to prevent it from being
+              // spilled.
+              LiveInterval &ImpLi = getInterval(ImpUse);
+              ImpLi.weight = HUGE_VALF;
+              MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true));
+            }
           }
         }
       }

Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=60596&r1=60595&r2=60596&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Fri Dec  5 11:41:31 2008
@@ -2141,8 +2141,6 @@
       // This doesn't work for several reasons.
       // 1. GlobalBaseReg may have been spilled.
       // 2. It may not be live at MI.
-      // 3. If this is used during register allocation / spilling, the spiller
-      // must know not to spill GlobalBaseReg (which is a temporary nasty hack).
       return false;
 
     // Create a v4i32 constant-pool entry.