[llvm-commits] [llvm] r72889 - /llvm/trunk/lib/CodeGen/RegAllocLinearScan.cpp

[Evan Cheng]

Author: evancheng
Date: Thu Jun  4 15:28:22 2009
New Revision: 72889

URL: http://llvm.org/viewvc/llvm-project?rev=72889&view=rev
Log:
A value defined by an implicit_def can be liven to a use BB. This is unfortunate. But register allocator still has to add it to the live-in set of the use BB.

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

Modified: llvm/trunk/lib/CodeGen/RegAllocLinearScan.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegAllocLinearScan.cpp?rev=72889&r1=72888&r2=72889&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/RegAllocLinearScan.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegAllocLinearScan.cpp Thu Jun  4 15:28:22 2009
@@ -542,6 +542,24 @@
     // Ignore splited live intervals.
     if (!isPhys && vrm_->getPreSplitReg(cur.reg))
       continue;
+
+    // A register defined by an implicit_def can be liveout the def BB and livein
+    // to a use BB. Add it to the livein set of the use BB's.
+    if (!isPhys && cur.empty()) {
+      if (MachineInstr *DefMI = mri_->getVRegDef(cur.reg)) {
+        assert(DefMI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF);
+        MachineBasicBlock *DefMBB = DefMI->getParent();
+        SmallPtrSet<MachineBasicBlock*, 4> Seen;
+        Seen.insert(DefMBB);
+        for (MachineRegisterInfo::reg_iterator ri = mri_->reg_begin(cur.reg),
+               re = mri_->reg_end(); ri != re; ++ri) {
+          MachineInstr *UseMI = &*ri;
+          MachineBasicBlock *UseMBB = UseMI->getParent();
+          if (Seen.insert(UseMBB))
+            UseMBB->addLiveIn(Reg);
+        }
+      }
+    }
     for (LiveInterval::Ranges::const_iterator I = cur.begin(), E = cur.end();
          I != E; ++I) {
       const LiveRange &LR = *I;