From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 5 Dec 2008 17:41:31 +0000 (+0000)
Subject: Reason #3 from 60595 doesn't hold true. If we can fold a PIC load from constpool... 
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=650d7f3ff4d22646def71b842f7f163c539e0aaf;p=oota-llvm.git

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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60596 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 31b300a7204..1df6c7d2732 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -2059,15 +2059,17 @@ addIntervalsForSpills(const LiveInterval &li,
           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));
+            }
           }
         }
       }
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 330b4d6ac85..9e60a0fe551 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -2141,8 +2141,6 @@ MachineInstr* X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
       // 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.